Boron in the Americas

Transcription

Boron in the Americas XV
Queen’s University
Kingston, ON, Canada
June 25-28, 2016
Program & Abstracts
Welcome
It is with great pleasure that we welcome you to Kingston, Ontario for the Boron in
the Americas XV conference at Queen’s University. We are honored to host the
first BORAM meeting held in Canada. Kingston was the first capital of Canada; rich
with history and natural wonders. We hope that you will enjoy the beautiful city of
Kingston as well as the three-day meeting packed with scientific sessions,
stimulating discussions, and opportunities to reconnect with friends or meet new
friends and colleagues.
One of the many facets of our program is the poster session and exhibition on
Sunday evening. This will be an excellent opportunity to mingle and discuss the
most recent advances in Boron research while enjoying complimentary beverages.
On Monday evening, we are excited to share the 1000 Islands Dinner Cruise, one
of Kingston’s premier dining experiences featuring a gourmet bistro style meal and
drinks as you travel along the Saint Lawrence River. Following the final session on
Tuesday afternoon, if you are still in town, please explore the many historical sites
and diverse local eateries in downtown Kingston, and the beautiful Lake Ontario.
Have a wonderful time at the BORAM XV conference and enjoy Kingston.
Professor Suning Wang
Conference Chair
Organizing Committee:
Prof. Cathleen Crudden, Prof. Victor Snieckus, Megan Bruce, Pam Bandy-Dafoe,
Deng-Tao Yang, Soren K. Mellerup
1
Generous Sponsorship for the BORAM XV
Conference has been provided by:
GOLD SPONSORS
SILVER SPONSORS
BRONZE SPONSORS
2
Schedule
3
4
Restaurants in Downtown Kingston
5
Tourist Attractions in Kingston
1. Bellevue House National Historic Site (the home to Canada’s First Prime
Minister Sir John A. MacDonald), 35 Centre St.
2. Queen’s University Clock Tower, 43 University Ave.
3. Murney Tower, Barrie St. and King St.
4. City Park, East of Queen’s Campus
5. City Hall, 216 Ontario St.
6. The Grand Theatre, 218 Princess Street
7. Kingston Trolley Tours, 1 Brock St.
8. Docks for Island Cruise (Banquet), 1 Brock St.
9. Ferry to Wolfe Island, Barrack St. and Ontario St. (Free ride)
10. Royal Military College, 13 General Crerar Cr.
11. Fort Henry, 1 Fort Henry Dr (a very beautiful site, 30-minute walk).
For the banquet and cruise on 27th,
please go to 1 Brock St to board
the boat (boarding time 5:20 PM).
It is number 8 on the map.
6
Conference Schedule
13:30-19:30
16:00-19:30
Saturday, June 25th
Registration
Chernoff Hall, 90 Bader Lane
Welcome Reception
Chernoff Hall, 90 Bader Lane
07:30-08:15
08:15-08:20
Sunday, June 26th
Breakfast, Leonard Hall
Opening Remarks
Session I
Session Chair: Matthias Wagner
08:20-08:45
OP1 - Douglas Stephan
University of Toronto, Canada
Exploiting FLP Reductions for Catalysis and Synthesis
08:45-09:10
OP2 - Gerhard Erker
Universität Münster, Germany
Frustrated Lewis Pairs: Principle and Some Recent Developments
09:10-09:20
SP1 - Jolie Lam, Benjamin Günther, Jeffrey M. Farrell, Rebecca L. Melen,
Douglas W. Stephan
Chiral Carbene–Borane Adducts: Towards Borenium Catalysts for Asymmetric
FLP Hydrogenations
09:20-09:45
OP3 - Patrick Eisenberger, Joshua Clarke, Brian Bestvater, Eric Keske, Adrian
Bailey, Cathleen M. Crudden
Queen’s University, Canada
Catalysis with Boro-Cations: Taking the F out of FLP
09:45-10:05
OP4 - Jonathan H. Barnard, Kexuan Huang, Sam Yruegas, Caleb D. Martin
Baylor University, USA
Investigating the Reactivity of Anti-Aromatic Boroles
10:05-10:20
Coffee Break, Chernoff Hall
Session II
Session Chair: Cathleen Crudden
10:20-10:45
OP5 - Martin Oestreich
Technische Universität Berlin, Germany
B(C6F5)3-Catalyzed Si–H Bond Activation
10:45-11:10
OP6 - Michael J. Ingleson
University of Manchester, UK
Catalytic and Stoichiometric C-B Bond Formation Using Boron Eletrophiles
11:10-11:20
SP2 - Daniel. L. Crossley, M. L. Turner, M. J. Ingleson
University of Manchester, UK
Synthesis and Photophysical Properies of Highly Emissive Organoboron
Oligomers and Polymers
11:20-11:45
OP7 - Stephen J. Geier, Christopher M. Vogels, Niall R. Mellonie, Simon Doherty,
Stephen A. Westcott
Mount Allison University, Canada
7
To B-E or not to B-E? Developing the Phosphinoboration Reaction
11:45-12:05
OP8 - Lewis C. Wilkins, Rebecca L. Melen
Cardiff University, UK
Reactivity of electron deficient boranes with π ‐bonds: cyclization, carboboration
and rearrangement
12:05-13:30
Lunch, Leonard Hall / Poster Set-up
Session III
Session Chair: Jens Müller
13:30-13:55
OP9 - Holger Braunschweig
University of Würzburg, Germany
Boron-Boron-Bonds: Unexpected Results and New Insights
13:55-14:20
OP10 - R. Bruce King, Alexandru Lupan
University of Georgia, USA
Metal-Metal Multiple Bonding in Dimetallaboranes
14:20-14:30
SP3 - Reid E. Messersmith, J. D. Tovar
Johns Hopkins University, USA
Competition for Aromaticity in Borepin-Fused Polycyclic Aromatics
14:30-14:55
OP11 - Webster L. Santos, Joseph A. Calderone, Amanda K. Nelson, Srinath
Pashikanti, Cheryl L. Peck, Russel Snead, Astha Verma
Virginia Tech, USA
Boron Activation in B-(B/Si) Bonds: Addition to C-C Multiple Bonds
14:55-15:15
OP12 - Audrey Ledoux, Paolo Larini, Christophe Boisson, Vincent Monteil, Jean
Raynaud, Emmanuel Lacôte
CNRS - Université de Lyon, France
Lewis Pair-assembled Boron-based polymers
15:15-15:30
Session IV
Session Chair: Todd Marder
15:30-15:55
OP13 - Shih-Yuan Liu
Boston College, USA
BN-Doping of Conjugated Carbon Rich Scaffolds
15:55-16:20
OP14 - Jian Pei
Peking University, China
Organic Semiconductors Based on Polycyclic Azaborines for Organic Field-Effect
Transistors
16:20-16:30
SP4 - Marco Nutz, Holger Braunschweig, Christopher W. Tate
Universität Würzburg, Germany
Reactivity of Terminal Group VI Arylborylene Complexes
16:30-16:40
SP5 - Hridaynath Bhattacharjee, Subhayan Dey, Jonathon D. Martell, Elaheh
Khozeimeh Sarbisheh, Jens Müller
University of Saskatchewan, Canada
Boron-Bridged Ferrocenophanes: Strained Monomers for Metallopolymers
8
16:40-17:00
OP15 - Jingwen Guan, Shin Homin, Keun Su Kim, Christa Homenick, M.
Plunkett, Malgosia Daroszewska, Christopher Kingston, Benoit Simard
National Research Council Canada, Canada
Chemistry on BNNT and BNNT-PC composite
17:00-17:20
OP16 - Pakkirisamy Thilagar
Indian Institute of Science (IISc), India
Structure-Property Correlations and Functional Opportunities of Aggregationinduced Emissive Organic/Organometallic Materials
17:20-19:30
Poster Session and Mixer, Chernoff Hall (1st floor)
07:30-08:20
Monday, June 27th
Session V
Session Chair: Frieder Jäkle
08:25-08:45
OP17 - Shigehiro Yamaguchi
Nagoya University, Furo, Japan
Chemistry of Boron-Doped Nanographenes
08:45-09:10
OP18 - Thomas Kaese, Esther v. Grotthuss, Matthias Wagner
Goethe-University Frankfurt, Germany
Redox Chemistry of Aryl(hydro)boranes
09:10-09:20
SP6 - Etienne Rochette, Nicolas Bouchard, Julien Légaré Lavergne, Marc-André
Légaré and Frédéric-Georges Fontaine
Université Laval, Canada
Design and synthesis of NR2-C6H4-BH2 Frustrated Lewis Pairs for the metal-free
catalytic C-H bond activation and borylation of heteroarenes
09:20-09:45
OP19 - Dennis Curran
University of Pittsburgh, USA
Synthesis and Reactions of N-Heterocyclic Carbene Boranes
09:45-10:05
OP20 - Thomas Cole
San Diego State University, USA
Additional Development to Functionalized Alkyl- and Alkenylboronic Derivatives
via Hydrodroboration
10:05-10:20
Session VI
Session Chair: Michael Ingleson
10:20-10:45
OP21 - Guy Lloyd-Jones, Paul Cox, Jorge Gonzalez, Andrew Leach
University of Edinburgh, UK
Heteroaromatic Boronic Acids in Aqueous-Organic Media
10:45-11:10
OP22 - Dennis G. Hall, You-Ri Kim, Taras Rybak, Samantha Kwok
University of Alberta, Canada
New Frontiers in Preparation and Coupling of Chiral Boronates for the Synthesis
of Bioactive Heterocycles
9
11:10-11:20
DP1 - Merle Arrowsmith, Dominic Auerhammer, Holger Braunschweig
CAAC: An Ideal Ligand for Stabilizing Highly Reactive Low-Valent Boron Species
11:20-11:45
OP23 - Mark S. Taylor
Selective reactions of carbohydrates using organoboron catalysts and promoters
11:45-12:05
OP24 - Frank Pammer, M. Grandl, Y. Sun
University of Ulm, Germany
Generation of N→B-Ladders via Regioselective Hydroboration
12:05-13:20
Lunch, Leonard Hall
13:20-13:30
Conference Photo (Atrium of Chernoff Hall)
Session VII
Session Chair: Shih-Yuan Liu
13:30-13:55
OP25 - Warren Piers, Denis Spasyuk, Laurent Maron, Christos Kefalidis, Michael
Neidig, Stephanie Carpenter
University of Calgary, Canada
Iron(III) Imido Radical Complexes of a Diborate Tetrapodal Pentadentate Ligand
Framework
13:55-14:20
OP26 -Thomas N Hooper, Nicholas A. Beattie, Stuart A. Macgregor, Andrew S.
Weller
University of Oxford, UK
B–H and P–H activation steps in phopshine–borane dehydropolymerization: What
you see is not what you first get.
14:20-14:30
SP7 - Matthew Morgan, Warren E. Piers
University of Calgary, Canada
Synthesis and Characterization of Boron-Nitrogen Containing Antiaromatic sIndacene Derivatives
14:30-14:55
OP27 - John Soderquist
University of Puerto Rico, USA
Asymmetric
Organoborane
Borabicyclo[3.3.2]decanes
Conversions
via
the
Amazing
14:55-15:15
OP28 - Donald S. Matteson
Washington State University, USA
HOCH2B(OH)2 and 2,5-Dihydroxy-1,4-dioxa-2,5-diborinane
15:15-15:30
Session VIII
Session Chair: Shih-Yuan Liu
15:30-15:55
OP29 - Todd Marder
Ruthenium-Promoted
Reduction
of
CO
to
Tetraborylmethane
Hexaborylethane and NHC-Mediated Cleavage of B-B Bonds
10
9-
and
15:55-16:20
OP30 - Atsushi Wakamiya, Hiroyuki Shimogawa, Yoshitaka Aramaki, Osamu
Yoshikawa, Takuhiro Taniguchi, Michihisa Murata, Yasujiro Murata
Kyoto University, Japan
Design and Synthesis of Functional Organoboron Materials with Intramolecular BN Coordination Bonds
16:20-16:30
SP8 - Soren Mellerup, Kang Yuan, Suning Wang
Queen’s University, Canada
Donor-Functionlized N,C-Organoboron Chelates: Exploring the Impact of
Substitution at Boron
16:30-21:00
Cruise and Banquet, Poster prize presentation, Boram award presentation
07:30-08:20
Tuesday, June 28th
Session IX
Session Chair: Stephen Westcott
08:25-08:45
OP31 - Frieder Jäkle
Rutgers University-Newark, USA
Organoboron Polymers as Supported Lewis Acids and Bases
08:45-09:10
OP32 - Yi Li, Shayu Li, Guoqiang Yang
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences,
China
Fluorescent temperature probes based on triarylboron compounds
09:10-09:20
SP9 - Stefanie Griesbeck, Zuolun Zhang, Tessa Lühmann, Marcus Gutmann,
Lorenz Meinel, Todd B. Marder
Julius-Maximilians Universität Würzburg, Germany
3-Coordinate Boron -Acceptors in Water-Soluble Chromophores for Live Cell
Imaging
09:20-09:45
OP33 - Trevor Janes, Yanxin Yang, Kimberly Osten, Maotong Xu, Adam
Pantaleo, Ellen Yan, Datong Song
CO2 insertion into the C-B bond of boronic esters
09:45-10:05
OP34 - Krishnan Venkatasubbaiah, Vanga Mukundam, Kunchala
Dhanunjayarao, Mamidala Ramesh
National Institute of Science Education and Research (NISER), India
New Tetra-coordinated Boron Complexes: Synthesis, Characterization and
Photophysical Properties
10:05-10:20
Session X
Session Chair: Debra Feakes
10:20-10:45
OP35 - David Schubert
U.S. Borax Inc., USA
New developments in the synthesis of industrial borates
10:45-11:10
OP36 - Sundargopal Ghosh
Indian Institute of Technology Madras, India
Triple Decker Sandwich Complexes Containing Six Membered Puckered and
Planar Ring
11
11:10-11:20
SP10 - Stephanie M. Barbon, Ryan R. Maar, Samantha Novoa and Joe B.
Gilroy
The University of Western Ontario, Canada
Molecular Materials Based on Boron Complexes of Formazanate Ligands
11:20-11:45
OP37 - Zuowei Xie
The Chinese University of Hong Kong, China
Transition Metal Catalyzed Selective B-H Activation and Functionalization of
Carboranes
11:45-12:05
OP38 - Mark W. Lee Jr.
University of Missouri, USA
Polyarylboranes: A New and Diverse Class of Organic-Inorganic Hybrid Materials
Exhibiting High Photoluminescence Efficiencies
12:05-13:30
Lunch, Leonard Hall
Session XI
Session Chair: Zuo-Wei Xie
13:30-13:55
OP39 - Yang-Jin Cho, So-Yoen Kim, Minji Cho, Won-Sik Han, Ho-Jin Son, Dae
Won Cho, Sang Ook Kang
Korea University, Korea
Aggregation-induced emission of diarylamino-π-carborane triads: effects of
charge transfer and π-conjugation
13:55-14:20
OP40 - Daniel G. Pruitt, Kristin Bullock, William A. Banks, Paul A. Jelliss
Saint Louis University, USA
Toward the Development of Rhenacarborane Complexes as CNS Drug Delivery
Agents
14:20-14:30
SP11 - Julian Böhnke, Holger Braunschweig, Theresa Dellermann, Kai
Hammond
Reactivity of Boron–Boron Multiple Bonds
14:30-14:55
OP41 - Alexander M. Spokoyny
University of California, Los Angeles, USA
Boron Cluster Chromophores and Photosensitizers
14:55-15:15
OP42 - Zaozao Qiu
Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, China
Reactivity of Novel Carboryne Precursor
15:15-15:30
Session XII
Session Chair: Webster Santos
15:30-15:55
OP43 - Xuenian Chen, Jin Wang, Ximeng Chen, Ruirui Wang, Congchao Cui,
Xiaoge Feng
Henan Normal University, China
Target Synthesis Boron/Nitrogen-Alkane Analogs
15:55-16:20
OP44 - Bhaskar C. Das, Mrinmay Chakrabarti, and Swapan K. Ray
The University of Kansas Medical Center, USA
Boron Containing Retinoids as Potential Therapeutics for Spinal Cord Injury
12
16:20-16:30
SP12 - Bijan Mondal, V. Ramkumar, Sundargopal Ghosh
Indian Institute of Technology Madras, India
Transition Metal Diborane Complexes: An Experimental and Quantum Chemical
Study
16:30-16:40
DP2 - Alain C. Tagne Kuate, Jiawei Chen, Roger A. Lalancette, Frieder Jaekle
Rutgers University – Newark, USA
Ferrocene-Based Planar Chiral Lewis Pair Systems
16:40-17:00
OP45 - Joel Dopke, Dorothy Buening, Kristen Westdorp, Richard Staples,
Alejandro Ramirez
Alma College, Alma, United States
Palladium-catalyzed Coupling Reactions of Iodododecaborates
17:00-17:20
Student Oral Presentation Prize Presentation
End of the Meeting
13
ORAL PRESENTATION ABSTRACTS
14
OP1 - Exploiting FLP Reductions for Catalysis and Synthesis
Douglas W. Stephan
Department of Chemistry
University of Toronto
80 St George St. Toronto, Ontario, M5S3H6
[email protected]
Frustrated Lewis pair (FLP) chemistry exploits unquenched reactivity of stericallyencumbered combinations of Lewis acids and bases to activate small molecules.1,2 This
discovery has led to the development of main group systems for catalytic reductions of a
growing breadth of organic substrates, including olefins, aromatic rings and polyaromatics. More recently we have developed several strategies to extend this to ketones.3–
6
While such reductions affords alcohols in high yields, efforts to apply this same strategies
to aromatic diones results in the stoichiometric reduction to generate new stable,
borocyclic radicals.8 The generality of this reactivity is probed and the chemistry of these
radicals has been examined and these results will be presented.
References:
(1)
Welch, G. C.; San Juan, R. R.; Masuda, J. D.; Stephan, D. W. Science 2006, 314,
1124.
(2)
McCahill, J. S. J.; Welch, G. C.; Stephan, D. W. Angew. Chem. Int. Ed. 2007, 46,
4968.
(3)
Stephan, D. W.; Erker, G. Angew. Chem. Int. Ed. 2015, 54, 6400.
(4)
Stephan, D. W. J. Am. Chem. Soc. 2015, 137, 10018.
(5)
Stephan, D. W. Acc. Chem. Res. 2015, 48, 306.
(6)
Bayne, J. M.; Stephan, D. W. Chem. Soc. Rev. 2015, 45, 765.
(7)
Longobardi, L. E.; Tang, C.; Stephan, D. W. Dalton Trans. 2014, 43, 15723.
(8)
Longobardi, L. E.; Liu, L.; Grimme, S.; Stephan, D. W. J. Am. Chem. Soc. 2016,
138, 2500.
15
OP2 - Frustrated Lewis Pairs: Principle and Some Recent
Developments
Prof. Gerhard Erker
Organisch-Chemisches Institut
Universität Münster
Corrensstr.40, Münster, Germany
Email: [email protected]
Lewis acids and bases can effectively be hindered from neutralizing adduct formation by
the attachment of very bulky substituents at their core atoms. The presence of an active
strong Lewis acid and a bulky strong Lewis base in the same solution can be utilized for
finding new cooperative reactions. A typical reaction that many such intra- or
intermolecular frustrated Lewis pairs (FLPs) undergo is heterolytic cleavage of dihydrogen
under mild conditions. In this lecture several examples of (mostly) intramolecular
phosphane (or amine)/borane FLPs are presented and their reactivity toward dihydrogen is
probed and the essential features of the metal-free dihydrogen splitting reaction are
discussed.
P/B FLPs undergo a variety of other reactions as well. Some recent examples of FLP
reactions with small molecules will be presented, including reactions with oxides of carbon,
nitrogen and sulfur. The chemistry of the resulting FLP reaction products derived from
these simple substrates will be outlined. Possible similarities of these metal-free reactions
with typical reactions at transition metal complexes will be discussed.
Bibliography
[1] "Intramolecular Frustrated Lewis Pairs: Formation, Structural and Chemical Features", G.
Kehr, S. Schwendemann, G. Erker, Top. Curr. Chem. 2013, 332, 45-83
[2] "Frustrated Lewis Pair Mediated Hydrogenations", D. W. Stephan, G. Erker, Top. Curr.
Chem. 2013, 332, 85-110
[3] "Radical Frustrated Lewis Pairs", T. H. Warren, G. Erker, Top. Curr. Chem. 2013, 334,
219-238
[4] "Frustrated Lewis pair chemistry of carbon, nitrogen and sulfur oxides", D. W. Stephan, G.
Erker, Chem. Sci. 2014, 5, 2625-2641
[5] "Frustrated Lewis Pair Chemistry: Development and Perspectives", D. W. Stephan, G.
Erker, Angew. Chem. Int. Ed. 2015, 54, 6400-6441
16
SP1 - Chiral Carbene–Borane Adducts: Towards Borenium Catalysts
for Asymmetric FLP Hydrogenations
Jolie Lam, Benjamin Günther, Jeffrey M. Farrell, Rebecca L. Melen, Douglas W.
Stephan*
80 St George St. Toronto, Ontario, M5S3H6
Email: [email protected], [email protected]
Amines and their derivatives are invaluable compounds to numerous industries, from
agrochemicals to pharmaceuticals. In particular, chiral products of interest for
pharmaceutical applications are required in high enantiopurity, which is typically achieved
by transition metal-mediated asymmetric transformations.1 N-heterocyclic carbene (NHC)stabilized borenium ions2 have recently been reported to be excellent metal-free catalysts
for the hydrogenation of imines under mild conditions by Stephan and coworkers. The
synthesis of new borenium ions that incorporate chiral substituents for the enantioselective
hydrogenation of prochiral imines were then targeted. Borenium cations stabilized by chiral
bisoxazoline-based3 carbenes and camphoric acid-derived carbenes were successfully
generated, as well as diisopinocampheylborane-based cationic boreniums.4 The synthesis
and efficacy of these systems in the asymmetric catalytic reduction of ketimines will be
discussed.
Bibliography
1.
Fleury-Brégeot, N.; Fuente, V.; Castillón, S.; Claver, C. ChemCatChem. 2010, 2,
1346-1371.
2.
Farrell, J. M.; Hatnean, J. A.; Stephan, D. W.. J. Am. Chem. Soc. 2012, 134,
15728-15731.
3.
Lindsay, D. M.; McArthur, D. Chem. Commun. 2010, 46, 2474-2476.
4.
Farrell, J. M.; Posaratnananthan, R. T.; Stephan, D. W. Chem. Sci. 2015, 6, 20102015.
17
OP3 - Catalysis with Boro-Cations: Taking the F out of FLP
Patrick Eisenberger, Joshua Clarke, Brian Bestvater, Eric
Keske, Adrian Bailey, Cathleen M. Crudden*
Kingston, ON, K7L 3N7, Canada
Boron has always been a central player in Lewis acid chemistry. Boranes containing
multiply fluorinated substituents such as B(C6F5)3 have proven highly effective for the
activation of unreactive bonds such as H–B,[1] H–Si,[2] and H–H[3] bonds and the
development in general of frustrated Lewis pair (FLP) chemistry[4]. Although this work has
been revolutionary in the area of catalysis, difficulties with the synthetic manipulation of
these electrophilic boranes has limited the field, with few exceptions, in terms of the design
of more functional group-tolerant boranes and enantioselective catalysis[5].
Thus the recent development of borenium ions, which are
trivalent positively charged boranes, is having a significant
Ph
N
N N
impact on the field.[6] Without needing to introduce a high
N Ph
number of fluorine atoms, and with several different synthetic
N
schemes available for their preparation, borenium ions are
B
B
O
O
rapidly expanding the scope of transformations that can be
[7]
catalyzed by boron-based catalysts. This presentation will
describe our recent work in this area.[8]
Bibliography
[1] (a) Blackwell, J. M.; Foster, K. L.; Beck, V. H.; Piers, W. E. J. Org. Chem. 1999, 64, 4887-4892. (b)
Parks, D. J.; Blackwell, J. M.; Piers, W. E. J. Org. Chem. 2000, 65, 3090-3098.
[2] (a) Denmark, S. E.; Ueki, Y. Organometallics, 2013, 32, 6631-6634. (b) Gandhamsetty, N.; Park,
S.; Chang, S. J. Am. Chem. Soc. 2015, 137, 15176–15184. (c) Ma, Y., Wang, B., Zhang, L. & Hou,
Z. J. Am. Chem. Soc. 2016, 138, 3663–3666.
[3] Welch, G. C.; San Juan, R. R.; Masuda, J. D.; Stephan, D.W. Science 2006, 314, 1124.
[4] Stephan, D. W.; Erker, G. in Frustrated Lewis Pairs I: Uncovering and Understanding, eds. Erker, G.
and Stephan, D. W., Springer-Verlag Berlin, Berlin, 2013, vol. 332, pp. V-V.
[5] (a) Liu, Y.B.; Du, H.G. J. Am. Chem. Soc., 2013, 135, 6810-6813. (b) Lindqvist, M.; Borre, K.;
Axenov, K.; Kotai, B.; Nieger, M. Leskela, M.; Papai, I.; Repo, T. J. Am. Chem. Soc., 2015, 137,
4038-4041. (c) Ghattas, G.; Chen, D.; Pan, F.; Klankermayer, J. Dalton Trans., 2012, 41, 90269028.
[6] (a) Koelle, P.; Noeth, H. Chem. Rev., 1985, 85, 399-418. (b) Piers, W. E.; Bourke, S. C.; Conroy,
K. D. Angew. Chem., Int. Ed., 2005, 44, 5016-5036. (c) De Vries, T. S.; Prokofjevs, A.; Vedejs, E.
Chem. Rev., 2012, 112, 4246-4282. (d) Ingleson, M. J., in Synthesis and Application of
Organoboron Compounds, eds. Fernandez, E. and Whiting, A., Springer-Verlag Berlin, Berlin,
2015, vol. 49, pp. 39-71.
[7] (a) Farrell, J.M.; Posaratnanathan, R.T.; Stephan, D.W. Chem. Sci., 2015, 6, 2010-2015. (b)
Farrell, J. M.; Hatnean, J.A.; Stephan, D.W. J. Am. Chem. Soc., 2012, 134, 15728-15731.
[8] (a) Eisenberger, P.; Bailey, A.M;. Crudden, C.M. J. Am. Chem. Soc., 2012, 134, 17384-17387.
(b) Eisenberger, P.; Bestvater, B.P.; Keske, E.C.; Crudden, C.M. Angew. Chem. Int. Ed., 2015, 54,
2467-2471. (c) Baptista de Oliveira Freitas, L.; Eisenberger, P.; Crudden, C.M. Organometallics,
2013, 32, 6635-6638.
18
OP4 - Investigating the Reactivity of Anti-Aromatic Boroles
Jonathan H. Barnard, Kexuan Huang, Sam Yruegas, and Caleb D.
Martin*
Department of Chemistry and Biochemistry
Baylor University
Waco, TX, 76798, USA
The anti-aromatic borole (1) was first reported in 1969, but its reactivity is not well
developed.1 Investigations have shown that boroles have very diverse reactivity. The
boron center is a powerful Lewis acid, the central ring can be reduced by one or two
electrons, and the butadiene can engage in Diels-Alder cycloadditions with dienophile
partners.2 We have explored the reactivity of boroles with 1,2-dipolar molecules such as
aldehydes, ketones, nitriles, isocyanides, isocyanates, and isothiocyanates.3 In some
cases, migration reactions and C-H bond activation occurred. For the majority, the reaction
proceeded via coordination of the nucleophilic site of the substrate, followed by a ring
expansion resulting from the attack of the nucleophilc endocyclic B-C bond to the
electrophilic site of the substrate to generate seven membered BNC5 or BOC5 rings (2).
Upon recognizing that boroles are effective reagents to generate larger boron-containing
unsaturated rings, we targeted the synthesis of six -electron heteroarenes. This method
proved to be effective for the preparation of 1,2-azaborines (3), 1,2-oxaborines (4), and
1,2-phosphaborines (5).4 The latter is the first example of this type of benzene analogue.
The mechanisms to form these species and properties of the novel heterocycles will be
discussed.
Bibliography
[1] J. J. Eisch, N. H. Hota and S. Kozima, J. Am. Chem. Soc. 1969, 91, 4575.
[2] a) H. Braunschweig and T. Kupfer, Chem. Commun., 2011, 47, 10903.; b) H.
Braunschweig, I. Krummenacher and J. Wahler, in Adv. Organomet. Chem., Eds. A. F. Hill
and M. J. Fink, Academic Press, San Diego, CA, 2013, Vol. 61, Ch. 1, pp. 1-53.
[3] a) K. Huang, C. D. Martin, Inorg. Chem., 2016, 55, 330.; b) K. Huang, S. A. Couchman, D.
J. D. Wilson, J. L. Dutton, C. D. Martin, Inorg. Chem., 2015, 54, 8957.; c) K. Huang, C. D.
Martin, Inorg. Chem., 2015, 54, 1869.
[4] a) S. A. Couchman, T. K. Thompson, D. J. D. Wilson, J. L. Dutton, C. D. Martin, Chem.
Commun., 2014, 11724.; b) J. H. Barnard, P. A. Brown, K. L. Shuford, C. D. Martin, Angew.
Chem. Int. Ed., 2015, 54, 12083.
19
OP5 - B(C6F5)3-Catalyzed Si–H Bond Activation
Martin Oestreich
Institut für Chemie
Technische Universität Berlin
Strasse des 17. Juni 115
10623 Berlin, Germany
Piers’ discovery that B(C6F5)3 catalyzes C=O hydrosilylation [1] opened a new chapter in
reduction methodology that still continues to grow.[2] Part of the fascination with this
reaction came from its at the time peculiar mechanism. Early insight had already
suggested that it proceeds through activation of the hydrosilane reagent by B(C6F5)3 rather
than conventional Lewis pair formation with the C=O substrate.[3] Over recent years, the
full mechanistic picture evolved,[4] and η1 coordination of the Si–H bond to B(C6F5)3
followed by SN2-Si displacement of hydride at the silicon atom with the C=O group as the
nucleophile is now well accepted. The borohydride emerging from that step is the actual
reducing agent, and chiral electron-deficient boranes are needed to render the hydride
transfer onto C=X groups enantioselective.
To date, asymmetric Piers C=O and also C=N hydrosilylations are elusive, and we
disclose here a solution to this long-standing problem.[5] We present the preparation of
axially chiral, C6F5-substituted borane catalysts [6] and discuss the mechanistic challenges
associated with these catalyses.[7]
Bibliography
[1] D. J. Parks, W. E. Piers, J. Am. Chem. Soc. 1996, 118, 9440.
[2] M. Oestreich, J. Hermeke, J. Mohr, Chem. Soc. Rev. 2015, 44, 2202.
[3] D. J. Parks, J. M. Blackwell, W. E. Piers, J. Org. Chem. 2000, 65, 3090.
[4] (a) S. Rendler, M. Oestreich, Angew. Chem. Int. Ed. 2008, 47, 5997. (b) K. Sakata, H.
Fujimoto, J. Org. Chem. 2013, 78, 12505. (c) A. Y. Houghton, J. Hurmalainen, A.
Mansikkamäki, W. E. Piers, H. M. Tuononen, Nat. Chem. 2014, 6, 983.
[5] L. Süsse, J. Hermeke, M. Oestreich, to be submitted for publication.
[6] (a) M. Mewald, R. Fröhlich, M. Oestreich, Chem. Eur. J. 2011, 17, 9406. (b) J. Hermeke,
M. Mewald, E. Irran, M. Oestreich, Organometallics 2014, 33, 5097.
[7] (a) M. Mewald, M. Oestreich, Chem. Eur. J. 2012, 18, 14079. (b) J. Hermeke, M. Mewald,
M. Oestreich, J. Am. Chem. Soc. 2013, 135, 17537.
20
OP6 - Catalytic and Stoichiometric C-B Bond Formation Using Boron
Eletrophiles
Michael J. Ingleson* and co-workers
School of Chemistry
University of Manchester
Manchester, M13 9PL, United Kingdom
The development of new routes to form C-B bonds enables the facile generation of
ubiquitous synthetic intermediates (boronic acids and derivatives)1 and novel functional
materials.2 We and others have utilized neutral and cationic boron electrophiles for the direct
(metal free) functionalization of pi nucleophiles.3,4,Our previous work focused on the C-H
electrophilic borylation of (hetero)arenes and the elemento-boration of alkynes. This
presentation will discuss our latest work in this area, including the development of: (i) new
alkyne elemento-boration reactions such as borylative cyclisation,5 trans-hydroboration6 and
trans-haloboration7; (ii) sequential electrophilic borylation of polyaromatic hydrocarbons to
generate boron containing functional materials7 (Figure 1); (iii) catalytic C-H borylation
reactions.7 These all require the use of strong boron electrophiles such as borenium cations
or their functional equivalents.
(X-Ray)
Figure 1: Triple electrophilic C-H borylation for the generation of fused planar materials
Bibliography
[1] Boronic Acids: Preparation and Applications, 2011, Ed. D. G. Hall
[2] A. Escande, M. J. Ingleson, Chem. Commun., 2015, 51, 6257
[3] T. S. De Vries, A. Prokofjevs, E. Vedejs, Chem. Rev., 2012, 112, 4246
[4] M. J. Ingleson, Top. Organomet. Chem., 2015, 49, 39.
[5] A. J. Warner, J. R. Lawson, V. Fasano, M. J. Ingleson, Angew. Chem. Int. Ed. 2015, 54,
11245.
[6] J. S. McGough, S. M. Butler, I. A. Cade, M. J. Ingleson, Chem. Sci., 2016,7, 3384
[7] Unpublished work
21
SP2 - Synthesis and Photophysical Properies of Highly Emissive
Organoboron Oligomers and Polymers
Daniel. L. Crossley, M. L. Turner,* M. J. Ingleson*
School of Chemistry,
The University of Manchester,
Manchester, M13 9PL, UK
Email: [email protected],
[email protected],
[email protected]
Four-coordinate boron compounds containing a chelating π-conjugated C,N donor and two
exocyclic aromatic moieties, termed (C,N-chelate)BAr2 have been extensively studied for
applications in optoelectronic devices [1] and as photoresponsive materials [2]. We will
present the incorporation of a boryl group into well studied and ubiquitous moieties in
donor-acceptor conjugated small molecules and polymers via a selective electrophilic C-H
borylation. This results in a large decrease in the band-gap of the material due to a
substantial decrease in the LUMO energy level (up to 1 eV) with a concomitant modest
increase in the HOMO energy level.[3] These low band-gap materials show near infra-red
emission with exceptionally high solid state quantum yield values (up to 44% at max ≥700
nm) and good solution processed OLED performance (>0.4% EQE). Furthermore, the
optoelectronic properties of 4-coorodinate C,N-chelate boranes can be modulated through
the judicious modification of the exocyclic aromatic substituent. Moreover, the arylation of
(C,N-chelate)BX2 (X = Cl or Br) using conventional transmetalation reagents (arylithium,
diarylzinc or aryl-Grignard reagents) can be problematic due to their sensitivity to protic
species and ill-defined structure which often result in a low yielding transmetalation.[4] We
therefore developed an efficient and versatile synthetic route to arylate (C,N-chelate)BX2
complexes utilizing a catalytic borenium mediated boro-desilylation/destannylation
reaction.[4]
Bibliography
[1] Y. L. Rao, Y.-L.; Wang, S. Inorg. Chem., 2011, 50, 12263-12274.
[2] Y. L. Rao, H. Amarne, S. Wang, Coord. Chem. Rev., 2012, 256, 759-770.
[3] D. L. Crossley, I. A Cade, E. R. Clark, A. Escande, M. J. Humphries, S. M. King, I. Vitorica-Yrezabal, M. J.
Ingleson, M. L. Turner, Chem. Sci., 2015, 6, 5144-5151.
[4] D. L. Crossley, J. Cid, L. D. Curless, M. L. Turner, M. J. Ingleson, Organometallics, 2015, 34, 5767-5774.
22
OP7 - To B-E or not to B-E? Developing the Phosphinoboration
Reaction
Stephen J. Geier,† Christopher M. Vogels,† Niall R. Mellonie,‡
Simon Doherty,‡ Stephen A. Westcott†*
†
Mount Allison University
Sackville, NB E4L 1G8, Canada
‡
NUCAT, School of Chemistry
Bedson Building
Newcastle University
Newcastle upon Tyne, NE1 7RU, England
Over the past two decades, the transition metal catalysed addition of boron-element (B-E,
where E = H, B, Sn, Si, etc) [1] bonds to unsaturated compounds has received a
considerable amount of attention. Given the intensity of interest in the reactivity of B-E
bonds it is somewhat surprising that relatively little is known about the analogous addition
chemistry of compounds containing single B-E bonds where E is phosphorus. The
corresponding phosphinoboration would introduce a P-C bond and a reactive B-C bond
that could be further elaborated to provide access to a host of useful structural motifs and,
in this regard, is a worthy target. The synthesis of phosphinoboronate esters containing a
single P-B bond is reported herein, together with reactivity studies towards a range of
organic substrates. We also discuss the transition metal catalysed phosphinoboration of CC multiple bonds in which P-C and B-C bonds are formed in a single step; allenes react via
a highly regioselective 1,2-addition while terminal alkynes give products where both P and
B groups have added to the same carbon atom [2].
References
[1] (a) Crudden, C. M.; Edwards, D. Eur. J. Org. Chem. 2003, 4695-4712. (b)
Fujihara, T.; Semba, K.; Terao, J.; Tsuji, Y. Catal. Sci. Technol. 2014, 4, 16991709. (c) Marder, T. B.; Norman, N. C. Top. Catal. 1998, 5, 63-73. (d) Suginome, M.;
Ohmura, T. In Boronic Acids 2nd Ed., (Ed. D. G. Hall) WILEY-VCH, Weinheim,
2011, pp. 171-212. (e) Oestreich, M.; Hartmann, E.; Mewald, M. Chem. Rev.
2013, 113, 402-441. (f) Ishiyama, T.; Nishijima, K.; Miyaura, N.; Suzuki, A. J.
Am. Chem. Soc., 1993, 115, 7219–7225.
[2] Daley, E. N.; Vogels, C. M.; Geier, S. J.; Decken, A.; Doherty, S.; Westcott, S. A.
Angew. Chem. Int. Ed. 2015, 54, 2121-2125.
23
OP8 - Reactivity of electron deficient boranes with π‐bonds: cyclization,
carboboration and rearrangement
Lewis C. Wilkins and Rebecca L. Melen*
School of Chemistry, Cardiff University
Main Building, Park Place
Cardiff, CF10 3AT, UK
Depletion of the π-electron density in alkenes and alkynes, by Lewis-acid (electrophile)
coordination, activates such groups to nucleophilic attack from amines, phosphines, thiols,
amides and/or other C-C π-bonds. In these reactions the Lewis acid and Lewis base
(nucleophile) undergo a 1,2-addition across the π-bond, reactivity that has been observed
in frustrated Lewis pair (FLP) chemistry.[1] Recently we have established that main group
Lewis acids are capable of activating C≡C π-bonds bearing intramolecular nucleophiles
towards cyclisation reactions yielding a diversity of heterocycles containing B, N and O
heteroatoms (Figure 1).[2-3] In some cases these heterocycles can be formed catalytically
in the absence of a transition metal.[2] Recent developments will be discussed.[1-4]
Figure 1. Cyclization reactions using boron Lewis acids.
Bibliography
[1] R. L. Melen, Chem. Commun., 2014, 50, 1161.
[2] R. L. Melen, M. M. Hansmann, A. J. Lough, A. S. K. Hashmi, D. W. Stephan, Chem.Eur. J., 2013, 19, 11928.
[3] M. M. Hansmann, R. L. Melen, F. Rominger, A. S. K. Hashmi, D. W. Stephan, J. Am.
Chem. Soc., 2014, 136, 777; M. M. Hansmann, R. L. Melen, F. Rominger, A. S. K.
Hashmi, D. W. Stephan, Chem. Commun., 2014, 50, 7243.
[4] M. M. Hansmann, R. L. Melen, M. Rudolph, F. Rominger, H. Wadepohl, D. W.
Stephan, A. S. K. Hashmi, J. Am. Chem. Soc., 2015, 137, 15469.
24
OP9 - Boron-Boron-Bonds: Unexpected Results and
New Insights
Holger Braunschweig
Institute of Inorganic Chemistry, University of Würzburg,
Am Hubland
D-97074 Würzburg, Germany
Due to its inherent electron deficiency, boron prefers non-classical bonding regimes when
combined to molecules with itself - in other words, boron forms polyhedral boranes, made
up of multicenter bonds, rather than chains or rings with electron-precise boron-boron
bonds. In the case of the latter, only very few well-defined examples have been published
over the past decades, which all suffer from low-yielding, non-selective syntheses that
solely rely on reductive coupling of amino(halo)boranes. Consequently, the area of
classical boron-boron multiple bonds is relatively undeveloped. Over the past four years
we have put significant effort into the development of new synthetic strategies to overcome
this seemingly element-specific deficiency.[1] Here, some new results on the formation of
B-B-double and –triple bonds will be presented together with some unusual results from
reactivity studies of the latter.[2]
Bibliography
[1] H. Braunschweig, F. Güthlein, Angew. Chem. Int. Ed. 2011, 50, 12613; Eur. Patent
EP2554547 (A1), 2013; H. Braunschweig, R. D. Dewhurst, K. Hammond, J. Mies, K.
Radacki, A. Vargas, Science 2012, 336, 1420; H. Braunschweig, Q. Ye, A. Vargas, R. D.
Dewhurst, K. Radacki, A. Damme, Nat. Chem. 2012, 4, 563; H. Braunschweig, T.
Dellermann, R. D. Dewhurst, W. C. Ewing, K. Hammond, J. O. C. Jimenez-Halla, T. Kramer,
I. Krummenacher, J. Mies, A. K. Phukan, A. Vargas, Nat. Chem. 2013, 5, 1025; H.
Braunschweig, R. D. Dewhurst, Angew. Chem. Int. Ed. 2013, 52, 3574.
[2] J. Böhnke, H. Braunschweig, T. Dellermann, W. C. Ewing, T. Kramer, I. Krummenacher,
A. Vargas, Angew. Chem. Int. Ed. 2015, 54, in press; P. Bissinger, A. Steffen, A. Vargas, R.
D. Dewhurst, A. Damme, H. Braunschweig, Angew. Chem. Int. Ed. 2015, 54, in press; P.
Bissinger, H. Braunschweig, A. Damme, C. Hörl, I. Krummenacher, T. Kupfer, Angew. Chem.
Int. Ed. 2015, 54, 359; J. Böhnke, H. Braunschweig, W. C. Ewing, C. Hörl, T. Kramer, I.
Krummenacher, J. Mies, A. Vargas, Angew. Chem. Int. Ed. 2014, 53, 9082; H.
Braunschweig, P. Bissinger, A. Damme, T. Kupfer, I. Krummenacher, A. Vargas, Angew.
Chem. Int. Ed. 2014, 53, 5689.
25
OP10 - Metal-Metal Multiple Bonding in Dimetallaboranes
R. Bruce Kinga and Alexandru Lupanb
a
University of Georgia
Athens, GA 30602 USA
b
Faculty of Chemistry and Chemical Engineering
Babeş-Bolyai University
Cluj-Napoca, Romania
Hypoelectronic dirhenaboranes and ditungstaboranes provide examples of
dimetallaboranes containing metal-metal multiple bonds. The skeletal bonding topology as
well as the Re=Re distances and Wiberg bond indices in the experimentally known
oblatocloso dirhenaboranes Cp2Re2Bn–2Hn–2 (Cp = 5-C5H5, n = 8 to 12)[1] suggest formal
Re=Re double bonds through the center of a flattened Re2Bn–2 deltahedron [2]. Removal
of a boron vertex from these oblatocloso structures leads to oblatonido structures such as
Cp2W 2B5H9 and Cp2W 2B6H10. In these oblatonido structures the central M=M double bond
is exposed to the outside through the hole generated by vertex removal. Similar removal
of two boron vertices from the Cp2Re2Bn–2Hn–2 (n = 8 to 12) structures generates
oblatoarachno structures such as Cp2Re2B4H8 and Cp2Re2B7H11. Higher energy Cp2Re2Bn–
5
2Hn–2 (Cp =  -C5H5, n = 8 to 12) structures exhibit closo deltahedral structures similar to
the deltahedral borane dianions BnHn2– [3]. The rhenium atoms in these structures are
located at adjacent vertices with ultrashort Re =
= Re distances similar to the formal
2–
quadruple bond found in Re2Cl8 by X-ray crystallography. Such surface Re =
= Re
!
quadruple bonds are found in the lowest energy PnRe2Bn–2Hn–2 structures (Pn =
5,5-pentalene) in which the pentalene ligand forces the rhenium atoms to occupy
adjacent deltahedral vertices [4].
!
!
Cp2Re2B8H8 (0.0 kcal/mol)
Re=Re 2.942 Å (WBI 0.47)
oblatocloso structure
Cp2Re2B8H8 (23.3 kcal/mol)
Re=
= Re 2.327 Å (WBI 1.94)
Bicapped tetragonal antiprism
PnRe2B7H7 (0.0 kcal/mol)
Re=
= Re 2.263 Å (WBI 2.18)
Bicapped tetragonal antiprism
Bibliography
[] B. Le Guennic, H. Jiao, S. Kahlal, J.-Y. Saillard, J.-F. Halet, S. Ghosh, M. Shang, A. M.
Beatty, A. L. Rheingold, T. P. Fehlner, J. Am. Chem. Soc. 2004, 126, 3203–3217.
[2] R. B. King, Inorg. Chem., 2006, 45, 8211–8216.
[3] A. Lupan, R. B. King, Inorg. Chem., 2012, 51, 7609–7616.
[4] A. Lupan, R. B. King, Organometallics, 2013, 32, 4002–4008.
26
SP3 - Competition for Aromaticity in Borepin-Fused Polycyclic
Aromatics
Reid E. Messersmith and J. D. Tovar*
Johns Hopkins University
3400 N. Charles St, Baltimore, MD 21218
Borepins are seven-membered, six -electron rings that are charge-neutral analogues of
the tropylium ion.1 The early years of borepin research (1960-1990s) uncovered
compounds with interesting properties but limited chemical stability. Recent work has
shown that borepins incorporated into polycyclic aromatic scaffolds with bulky protecting
groups on the boron atom can lead to compounds that are stable to air, water and column
chromatography and maintain ambient stability for months.2 These compounds have
allowed for further investigation of the physical properties of borepins and a more complete
understanding of the fundamental aspects of aromaticity. We have synthesized four novel
thieno-, benzo- and naphtho- fused borepins and evaluated their spectroscopic,
crystallographic and electrochemical properties. By comparing differentially fused borepins,
we can observe the impact of thiophene vs. carbocyclic ring fusions and the impact it has
on the aromaticity of the borepin ring.
References:
1. Messersmith, R. E.; Tovar, J. D., J. Phys. Org. Chem. 2015, 28, 378-387.
2. (a) Mercier, L. G.; Piers, W. E.; Parvez, M., Angew. Chem. Int. Ed. 2009, 48, 6108-6111;
(b) Caruso, A.; Siegler, M. A.; Tovar, J. D., Angew. Chem. Int. Ed. 2010, 49, 4213-4217; (c)
Levine, D. R.; Siegler, M. A.; Tovar, J. D., J. Am. Chem. Soc. 2014, 136, 7132-7139.
3. Messersmith, R. E.; Siegler, M. A.; Tovar, J. D., Submitted 2016
27
OP11 - Boron Activation in B-(B/Si) Bonds: Addition to C-C Multiple
Bonds
Webster L. Santos,* Joseph A. Calderone, Amanda K. Nelson, Srinath
Pashikanti, Cheryl L. Peck, Russel Snead, Astha Verma
Virginia Tech
Blacksburg, VA 24061, USA
Vinylboronic acid and vinylsilane derivatives are an important class of synthetic building
blocks in organic synthesis, particularly with Suzuki-Miyaura and Hiyama cross coupling
reactions.1 Therefore, methods toward their synthesis is vital. Our laboratories have been
focused on developing sustainable methods for the synthesis of these important class of
compounds. In particular, protocols that are transition metal-free or utilize earth abundant
copper instead of transition metals such as platinum or palladium are highly desirable.
Further, water is used as the solvent as much as possible. A key feature of our chemistry
is the Lewis base activation of boron in diboron or borylsilane reagents to effect
stereoselective synthesis of vinylboron or silane derivatives. This presentation will disclose
our recent findings and discuss mechanistic investigations.2
Bibliography
(1) (a) Barbero, A.; Pulido, F. J. Acc. Chem. Res. 2004, 37, 817; (b) Fleming, I.
Organocopper Reagent; Oxford University Press: New York, 1994; (c) Denmark, S. E.; Liu,
J. H. C. Angew. Chem. Int. Ed. 2010, 49, 2978; (d) Lennox, A. J. J.; Lloyd-Jones, G. C.
Chem. Soc. Rev. 2014, 43, 412.
(2) (a) Nelson, A. K.; Peck, C. L.; Rafferty, S. M.; Santos, W. L. J. Org. Chem. 2016,
10.1021/acs.joc.6b00648; (b) Peck, C. L.; Calderone, J. A.; Santos, W. L. Synthesis 2015,
47, 2242; (c) Pashikanti, S.; Calderone, J. A.; Nguyen, M. K.; Sibley, C. D.; Santos, W. L.
Org. Lett. 2016, DOI:10.1021/acs.orglett.6b00981. (d) Snead, R.; Verma, A.; Dai, Y.;
Rastatter, B.; Santos, W.L. manuscript in preparation.
28
OP12 - Lewis Pair-assembled Boron-based polymers
Audrey Ledoux, Paolo Larini, Christophe Boisson, Vincent
Monteil, Jean Raynaud,* Emmanuel Lacôte*
Laboratoires C2P2 & LHCEP
CNRS - Université de Lyon
43 Bd du 11 novembre 1918, Villeurbanne, France
Boron-based polymers have been the focus of growing attention because they exhibit
outstanding properties, such as photoluminescence, electroluminescence, nonlinear
optical properties, n-type semiconductivity, etc. that make them well-suited as materials for
organic electronics, imaging, or ion and molecule sensing.[1] A vast majority of the former
derive from B-containing monomers polymerized via free radical additions, or
organometallic couplings.[1] That is, their main chain contain only covalent bonds. We
harnessed new boron polymers built from monomers assembled on long-range via Lewis
pairs. We selected N and B hydrogen-disubstituted amine-boranes in poly-Lewis paired
polymers. Examples of poly(amine-borane)s or polyboramines are limited to the use
bipyridines or pyrazines with aryl/aliphatic bisborane monomers.[2] Most of these polymers
are synthesized by precipitation methods and have a poor stability in solution. Therefore
none of them were extensively characterized.
We will discuss a new type of polyboramines, featuring N and B bis-hydrogenated
bricks.[3] The polymers are soluble and stable in THF and DMSO and they can be
dihydrogen storing materials.
Bibliography
[1] a) F. Jäkle, Chem. Rev. 2010, 110, 3985-4022; b) Y. Qin, F. Jäkle, J. Inorg. Organomet. Polym.
Mater. 2007, 17, 149-157; c) F. Cheng, E.M. Bonder, F. Jäkle, J. Am. Chem. Soc. 2013, 135, 1728617289 ; d) W. Wan, F. Cheng, F. Jäkle, Angew. Chem. Int. Ed. 2014, 53, 8934-8938; e) F. Jäkle, Top.
Organomet. Chem. (Springer) 2015, 49, 297-325.
[2] a) S. Itsuno, T. Sawada, T. Hayashi, K. Ito, J. Inorg. Organomet. Polym. 1994, 4, 403-414 ; b) Y.
Chujo, I. Tomita, N. Murata, H. Mauermann, T. Saegusa, Macromolecules 1992, 25, 21-32 ; c) N.
Matsumi, Y. Chujo, Macromolecules 1998, 31, 3802-3806 ; d) M. Grosche, E. Herdtweck, F. Peters, M.
Wagner, Organometallics 1999, 18, 4669-4672 ; e) E. Sheepwash, V. Krampl, R. Scopelliti, O. Sereda,
A. Neels, K. Severin, Angew. Chem. Int. Ed. 2011, 50, 3034-3037.
[3] Audrey Ledoux, Paolo Larini, Christophe Boisson, Vincent Monteil, Jean Raynaud, Emmanuel
Lacôte, Angew. Chem. Int. Ed. 2015, 54, 15744-15749.
29
OP13 - BN-Doping of Conjugated Carbon Rich Scaffolds
Shih-Yuan Liu
Boston College
Chestnut Hill, MA, 02467 USA
BN/CC isosterism, which is the replacement of a CC bond unit with the isoelectronic and
isostructural BN bond unit, has emerged as a viable strategy to increase the chemical
space of compounds relevant to materials science.[1,2] We are focused on introducing the
BN unit in conjugated carbon-rich scaffolds. I will describe our efforts in the development
of synthetic strategies for BN doping of simple acenes and naphthalenes.[3,4] Furthermore,
the synthesis of donor-acceptor-substituted monocyclic 1,4-azaborines as BN isosteres of
substituted para-terphenyls and their photophysical characterization will be described.[5]
The consequence of BN/CC isosterism of these carbon-rich materials on the electronic
structure will be discussed as well.
Bibliography
[1] X.-Y. Wang, J.-Y. Wang, J. Pei, Chem. Eur. J. 2015, 21, 3528.
[2] P. G. Campbell, A. J. V. Marwitz, S.-Y. Liu, Angew. Chem. Int. Ed. 2012, 51, 6074.
[3] J. S. A. Ishibashi, J. L. Marshall, A. Maziere, G. J. Lovinger, B. Li, L. N. Zakharov, A.
Dargelos, A. Graciaa, A. Chrostowska, S.-Y. Liu, J. Am. Chem. Soc. 2014, 136, 15414.
[4] A. N. Brown, B. Li, S. Y. Liu, J. Am. Chem. Soc. 2015, 137, 8932.
[5] X. Liu, Y. Z., B. Li, L. N. Zakharov, M. Vasiliu, D. A. Dixon, S.-Y. Liu, Angew. Chem. Int.
Ed. 2016, 55, ASAP.
30
OP14 - Organic Semiconductors Based on Polycyclic Azaborines for
Organic Field-Effect Transistors
Prof. Dr. Jian Pei
College of Chemistry and Molecular Engineering
Peking University
Beijing 100871, China
Recently, azaborine chemistry, which employs a B–N bond as a substitute of the C=C bond
in benzene rings, has attracted great interest due to its fundamental importance for the
understanding of aromaticity and potential applications in hydrogen storage and biomedical
research. Meanwhile, the BN substitution strategy in polycyclic aromatic systems has
provided a number of interesting compounds with modified optoelectronic properties and
intermolecular interactions. These advances have triggered the research on polycyclic
azaborine compounds for electronic devices, e.g. organic field-effect transistors (OFETs) and
organic light-emitting diodes (OLEDs) since 2013. However, this direction is quite in its
infancy, and there is still a strong demand for materials development and the structureproperty relationship study.
Recently, we introduced the concept of replacing the CC unit with its isoelectronic BN unit in
organic π-systems and developed some BN-substituted polycyclic aromatics and polymers.
BN substitution has shown to be effective in modulating the photophysical and redox
properties as well as intermolecular interactions of conjugated molecules, thus providing a
new family of BN-embedded polycyclic aromatics with intriguing properties. Importantly, the
applications of such materials in electronic devices have been demonstrated very recently,
which opened up new possibilities for organic electronics. Currently, research on the device
applications and charge transport properties of BN-embedded polycyclic aromatics is at its
infancy. It is still limited by the poor materials accessibility due to the synthetic challenges.
Efficient synthetic strategies are needed to enrich the chemical diversity of BN-containing
compounds. With rationally designed molecules and in-depth investigation of the structureproperty relationship, it is expected that BN-substituted polycyclic aromatics will provide new
opportunities for organic electronics with high performance and unique functionality.
Bibliography
[1] X.-Y. Wang, H.-R. Lin, T. Lei, D.-C. Yang, F.-D. Zhuang, J.-Y. Wang, S.-C. Yuan, J. Pei, Angew.
Chem. Int. Ed. 2013, 52, 3117.
[2] X.-Y. Wang, F.-D. Zhuang , R.-B. Wang , X.-C. Wang , X.-Y. Cao, J.-Y. Wang, J. Pei, J. Am. Chem.
Soc. 2014, 136, 3764.
[3] X.-Y. Wang, J.-Y. Wang, J. Pei, Chem. Euro. J. 2015, 21, 3528.
[4] X.-Y. Wang, F.-D. Zhuang, J.-Y. Wang, J. Pei, Chem. Comm. 2015, 51, 17532.
[5] X.-Y. Wang, F.-D. Zhuang, X.-C. Wang, X.-Y. Cao, J.-Y. Wang, J. Pei , Chem. Comm. 2015, 51,
4368.
31
SP4 - Reactivity of Terminal Group VI Arylborylene
Complexes
Marco Nutz, Holger Braunschweig,* Christopher W. Tate
Universität Würzburg
97074 Würzburg, Germany
Bulky group VI arylborylene complexes (1) show remarkable reactivity towards various
substrates. Reduction, borylene transfer to unsaturated organic compounds and even
liberation of the borylene ligand can be achieved.1,2,3
Reduction of borylene complexes leads to heterocoupling between a borylene and
carbonyl ligands yielding a dianionic chromium complex. Using 1 as borylene source in
transfer reactions to unsaturated organic compounds a variety of compounds can be
isolated. The reaction of 1 with diphenylacetylene leads to the first example of a complex
containing a ɳ3-coordinated borirene ligand, whereas reaction with diisopropylcarbodiimide
yields a room-temperature-stable iminoborane or ‒ if smaller carbodiamides are used ‒
diazadboraetidine.4
Donor molecules such as isocyanides, carbonmonoxide or N-heterocyclic carbenes give
rise to a number of unprecedented monovalent boron species. Depending on the steric
demand of the Lewis base/or the boron substituent, homoleptic or heteroleptic compounds
are formed, that all show trigonal planar geometry of the boron atom. Analysis of the
frontier orbitals indicates that the HOMO level consists of a three-centered -bonding
interaction between the boron and the attached ligands. Further computational
investigations show extensive boron-to-ligand -backbonding, underlining the monovalent
character of the boron atom in these molceules.1
Bibliography
[1]
H. Braunschweig, R. D. Dewhurst, F. Hupp, M. Nutz, K. Radacki, C. W. Tate, A. Vargas, Q. Ye,
Nature 2015, 522, 327–330.
[2]
H. Braunschweig, R. D. Dewhurst, C. Hörl, K. Radacki, C. W. Tate, A. Vargas, Q. Ye,
Angew. Chem. Int. Ed. 2013, 52, 10120–10123.
[3]
H. Braunschweig, R. D. Dewhurst, K. Radacki, C. W. Tate, A. Vargas, Angew. Chem. Int.
Ed. 2014, 53, 6263–6266.
[4]
H. Braunschweig et al., unpublished results.
32
SP5 - Boron-Bridged Ferrocenophanes: Strained Monomers for
Metallopolymers
Hridaynath Bhattacharjee, Subhayan Dey, Jonathon D. Martell,
Elaheh Khozeimeh Sarbisheh, and Jens Müller*
Department of Chemistry,University of Saskatchewan, Saskatoon, SK,
S7N5C9, Canada
Email(s): [email protected], [email protected]
Incorporating metals in synthetic polymers can impose a diverse range of different new and
valuable properties.1 Organometallic polymers containing three-coordinate boron have the potential
for intriguing electronic and optical properties associated with the electron deficient nature of the
boron centers.2 Boron-containing conjugated polymers can potentially be obtained via ring-opening
polymerization (ROP) of strained boron-bridged [n]ferrocenophanes ([n]FCPs). The first three
boron-bridged [1]FCPs (type 1) were reported almost two decades ago.3 Unfortunately, thermal
ROP of those highly strained monomers resulted only in some insoluble materials which brought the
chemistry to a standstill.3b Recently, our group has resumed this chemistry by developing flexible
approaches to synthesize new boron-bridged [1]FCPs as starting materials for controlled ROPs.4 In
this approach, our strategy was to add alkyl groups on the Cp rings to provide steric protection to
the bridging moiety and also to increase the solubility of the monomers as well as the resulting
polymers. Detailed studies were done by fine tuning of the bulk on Cp rings as well as the reaction
conditions in order to understand the mechanism of the formation of strained [1]FCPs (type 2).5
So far, all reported boron-bridged [1]FCPs contain amino-group stabilized boron moieties. This
electronic stabilization from the nitrogen atom led us to our recent discovery of
azabora[2]ferrocenophanes (type 3).6 Very recently, we have succeeded to synthesize the first
examples of such species, including one where the boron is rather protected by a bulky group than
an amino group.
In this contribution, our in-depth understanding of the mechanism of the salt-metathesis reactions,
recent unprecedented syntheses of azabora[2]ferrocenophanes, and some indication of the
formation of steric protected boron-bridged [1]FCPs will be discussed.
References:
1.
Whittell, G. R.; Hager, M. D.; Schubert, U. S.; Manners, I. Nat. Mater. 2011, 10, 176.
2.
Jäkle, F. Chem. Rev. 2010, 110, 3985.
3.
(a) Braunschweig, H.; Dirk, R.; Müller, M.; Nguyen, P.; Resendes, R.; Gates, D. P.; Manners, I.
Angew. Chem., Int.
Ed. 1997, 36, 2338; (b) Berenbaum, A.; Braunschweig, H.; Dirk, R.; Englert, U.; Green, J. C.; Jäkle,
F.; Lough, A. J.; Manners, I. J. Am. Chem. Soc. 2000, 122, 5765.
4.
Sadeh, S.; Bhattacharjee, H.; Khozeimeh Sarbisheh, E.; Quail, J. W.; Müller, J. Chem. Eur. J. 2014,
20, 16320.
5.
Bhattacharjee, H.; Martell, J. D.; Khozeimeh Sarbisheh, E.; Sadeh, S.; Quail, W. J.; Müller, J.
unpublished results.
6.
Bhattacharjee, H.; Dey, S.; Sun, W.; Müller, J. unpublished result.
33
OP15 - Chemistry on BNNT and BNNT-PC composite
Jingwen Guan,*1 Shin Homin,1 Keun Su Kim,1 Christa Homenick,1 M.
Plunkett,1 Malgosia Daroszewska,1 Christopher Kingston1 and
Benoit Simard1
1
Security and Disruptive Technology Portfolio, National Research
Council Canada, 100 Sussex Drive, Ottawa, ON K1A 0R6
Boron nitride nanotubes are isoelectronic with carbon nanotubes. Hence, they exhibit
similar structural characteristics: seamless hollow structures with superlative mechanical
properties. But, they also have important differences such as different band gap structures,
thermal and chemical stability. Many of these differences can be traced to the difference
in the electron distribution. Whereas CNT are fully aromatic, BNNT exhibit local charge
separation with a partially emptied p-orbital on B. Hence, not surprisingly, the chemistry of
BNNT is very much different from that of CNT. In our quest to develop chemical schemes
for the covalent functionalization of BNNT, we recently examined theoretically and
experimentally the chemistry of reduced BNNT. After reviewing the electron distribution in
BNNT, we will show how the addition of single electron enhances dramatically the binding
towards some specific radicals and the nucleophilic character towards alkyl halides. BNNT
are thermally very resistant against oxidation. Whereas CNT decompose into CO2 at
temperature around 500oC, BNNT are highly stable in air to at least 900°C without
degradation and in flames up to 2000oC for several minutes.
Bibliography
[1] K. S. Kim et. al. ACS NANO. 2014, 8(6), 6211-6220.
[2] H. Shin et al., ACS NANO. 2015, 9(12), 12573-12582.
34
OP16 - Structure-Property Correlations and Functional Opportunities of
Aggregation-induced Emissive Organic/Organometallic Materials
P. Thilagar
Department of Inorganic and Physical Chemistry
Indian Institute of Science (IISc)
Bangalore, 560012, India
Applications of organic/organometallic materials in optoelectronic systems demand their
compatibilities in solid-state. Thus, solid-state emissive luminescent materials have found
significant importance in recent times owing to their potential applications in OLEDs
(organic light-emitting diodes), security, sensor systems etc.1 In general, most fluorescent
dyes are found to show negligible fluorescence in their solid-state resulting from closerange intermolecular interactions, self-absorption and energy-transfer processes.1
Synthetic control over such cumulative behaviour of dyes is a challenging task. Systematic
alteration of configuration, conformation and functionalization of molecules can be
effectively used to understand structure-property relationships and the regulatory aspects
of solid-state luminescent dyes.
In our works, we have developed several systematic strategies in order to gain insights
the molecular and cumulative luminescent properties of organic and organometallic dyes.
In course of these investigations, we have also investigated the balanced recipes of
obtaining AIEE (aggregation-induced emission enhancement), AIES (aggregation-induced
emission switching), FONs (fluorescent organic nano-aggregates) and piezochromic
luminescent properties in notably small and easily accessible molecular architectures
based on BODIPYs (boron-dipyrromethenes), NPIs (1,8-naphthalimides) and TABs
(Triarylboranes).3 In this talk, some quite interesting aspects of AIEE materials would be
presented.
Bibliography
[1]
D. Yan, D. G. Evans, Mater. Horiz., 2014, 1, 46-57. (b) S. Varughese, J. Mater.
Chem. C, 2014, 2, 3499-3516. (c) S. Mukherjee, P. Thilagar, Dyes Pigm., 2014, 110, 2-27.
(d) S. Mukherjee, P. Thilagar, Chem. Commun., 2015, 51, 10988-11003. S. Mukherjee, P.
Thilagar J. Mater. Chem. C, (2015), DOI:10.1039/c5tc02406d
[2] J. R. Lakowicz, Principles of Fluorescence Spectroscopy, Springer, Singapore, 2006.
[3](a) C. A. Swamy P, S. Mukherjee, S. Sinha and P. Thilagar. J. Mat. Chem. C, 2013, 1,
4691-4698. (b) S. Mukherjee and P. Thilagar. Chem. Commun., 2013, 49, 7292-7294. (c) S.
Mukherjee and P.Thilagar. Phys. Chem. Chem. Phys., 2014, 16, 20866-20877. (d) S.
Mukherjee and P. Thilagar. Chem. Eur. J., 2014, 20, 8012-8023. (e) S. Mukherjee and P.
Thilagar. Chem. Eur. J., 2014, 20, 9052-9062. (f) C. A. Swamy P and P. Thilagar, Chem. Eur.
J., 2015, 21 (24), 8874–8882. (f) P. Thilagarand S. Mukherjee, Chem. Commun., 2015, DOI:
10.1039/C5CC03114A,
35
OP17 - Chemistry of Boron-Doped Nanographenes
Shigehiro Yamaguchi
Institute of Transformative Bio-Molecules (ITbM)
Nagoya University
Furo, Chikusa, Nagoya 464-8602, Japan
Incorporation of a group 13 boron atom into a -conjugated skeleton is a powerful strategy
to develop new photo- or electro-functional organic materials with electron-deficient
characters. In this chemistry, one of the attractive target -electron systems may be borondoped graphenes. The doping of the electron-deficient boron atoms into the graphene
framework would impart semi-conducting properties or some additional intriguing
properties or functions. However, chemistry of this material type is still in infancy from the
fundamental point of view. In this context, we have recently succeeded in the synthesis of
a series of planarized triarylboranes that can be regarded as the model boron-doped
graphene flakes [1]. Notably, despite the absence of any steric protecting group on the
boron atom, this class of molecules showed unusual stabilities against water, oxygen, and
silica gel. The remarkable stabilities are due to the “structural constraint” around the boron
atom, which is a new solution to overcome intrinsic instability of boron-containing electron systems [2]. In this presentation, some progress in this chemistry, including
chemisorption properties [3], solution-processed fabrication of devices, and charge carrier
transport [4], will be discussed.
Bibliography
[1] (a) C. Dou, S. Saito, K. Matsuo, I. Hisaki, S. Yamaguchi, Angew. Chem. Int. Ed., 51,
12206 (2012). (b) C. Dou, S. Saito, S. Yamaguchi, J. Am. Chem. Soc., 135, 9346 (2013).
(c) K. Matsuo, S. Saito, S. Yamaguchi, J. Am. Chem. Soc., 136, 12580 (2014). (d) S.
Kawai, S. Saito, S. Osumi, S. Yamaguchi, A. S. Foster, P. Spijker, E. Meyer, Nat.
Commun., 6, 8098 (2015).
[2] Z. Zhou, A. Wakamiya, T. Kushida, S. Yamaguchi, J. Am. Chem. Soc., 134, 4529 (2012).
[3] S. Osumi, S. Saito, C. Dou, K. Matsuo, K. Kume, H. Yoshikawa, K. Awaga, S. Yamaguchi,
Chem. Sci., 7, 219 (2016).
[4] T. Kushida, A. Shuto, M. Yoshio, T. Kato, S. Yamaguchi, Angew. Chem. Int. Ed., 54, 6922
(2015).
36
OP18 - Redox Chemistry of Aryl(hydro)boranes
Thomas Kaese, Esther v. Grotthuss, Matthias Wagner*
Goethe-University Frankfurt
60438 Frankfurt/Main, Germany
Hydroboration reactions of alkyl(hydro)boranes are among the most useful methods in
organic synthesis. In contrast, the potential of aryl(hydro)boranes is only now starting to be
exploited.
As a result of the conjugative overlap between the vacant boron p orbital and the electron clouds of the aryl substituents, numerous arylboranes are highly emissive in the
visible range of the electromagnetic spectrum. At the same time, they tend to be good
electron acceptors. In some aryl(hydro)boranes, these favorable optoelectronic properties
are still preserved. Moreover, the hydrogen substituents offer additional options for
derivatization. Apart from hydroboration protocols, the introduction of hydrogen atoms at
boron often induces substituent redistribution reactions that provide facile access to
otherwise hard-to-obtain molecular scaffolds.
Our group has recently shown that also the reduction of aryl(hydro)boranes, such as A,
can be an efficient mode of derivatization. Apart from the formation of B‒B single and B=B
double bonds, electron-induced rearrangement reactions lead to unprecedented species.
Moreover, NHC-adducts of suitably preorganized ditopic boranes (cf. B) give access to
polycyclic aromatic hydrocarbons with integrated diborane(4) units via radical coupling
reactions. Finally, we have employed doubly reduced 9,10-dihydro-9,10diboraanthracenes (cf. C) as one-component FLPs, in which the two excess electrons take
the role of the Lewis base. Further details will be presented in this lecture.
Bibliography
[1] J. Am. Chem. Soc. 2011, 133, 4596.
[2] Angew. Chem. Int. Ed. 2012, 51, 12514.
[3] Angew. Chem. Int. Ed. 2014, 53, 10408.
[4] J. Am. Chem. Soc. 2015, 137, 3705.
[5] Perspectives article: Dalton Trans. 2012, 41, 6048.
37
SP6 - Design and synthesis of NR2-C6H4-BH2 Frustrated Lewis Pairs for
the metal-free catalytic C-H bond activation and borylation of
heteroarenes
Etienne Rochette, Nicolas Bouchard, Julien Légaré Lavergne, Marc-André Légaré
and Frédéric-Georges Fontaine*
Département de chimie and Centre de recherche en Catalyse et Chimie Verte (C3V)
Université Laval
Québec, QC, G1V 0A6, Canada
E-mail: [email protected], [email protected]
Frustrated Lewis pairs (FLPs), are well known for their ability to activate small molecules,
notably hydrogen,[1] which lead to their use in many systems of catalytic metal-free
hydrogenation.[2] Recently, our research group extended the use of FLPs to include the
activation and catalytic borylation of the Csp2-H bond of hetero-arenes using 2,2,6,6tetramethylpiperidno-C6H4-BH2 as catalyst.[3] The recent developments concerning the
synthesis and activity of bench stable pre-catalysts[4] as well as the design, synthesis and
reactivity of a variety of new NR2-C6H4-BH2 will be discussed.
Bibliography
[1] Welch, G.C.; San Juan, R.; Masuda, J.D.; Stephan, D.W. Science 2006, 314, 1124-1126.
[2] Stephan, D. W.; Erker, G. FLP chemistry: Topics in Current Chemistry;
Eds.; Springer: New York, 2013; Vols, 332, and 334.
[3] Légaré, M.-A.; Courtemanche, M.-A.; Rochette, É.; Fontaine, F.-G. Science 2015, 349,
513-516.
[4] Légaré, M.-A.; Rochette, É.; Lavergne, J. L.; Bouchard, N.; Fontaine, F.-G. Chem.
Commun. 2016, DOI: 10.1039/C6CC01267A.
38
OP19 - Synthesis and Reactions of N-Heterocyclic Carbene Boranes
Dennis P. Curran
University of Pittsburgh
Pittsburgh, PA 15208 USA
Boranes are common Lewis acids and N-heterocyclic carbenes are popular Lewis bases,
so it is surprising that their complexes—N-heterocyclic carbene boranes—were little
studied until recently.1 An overview of recent progress on the chemistry of N-heterocyclic
carbene boranes will be provided. They are proving to be interesting reagents for radical
reactions (for example, reductive decyanations2 as shown below), ionic reactions (for
example, hydroborations of arynes3) and organometallic reactions (for example, Suzuki
reactions4).
Bibliography
[1] Curran, D. P.; Solovyev, A.; Makhlouf Brahmi, M.; Fensterbank, L.; Malacria, M.; Lacôte, E.
Angew. Chem. Int. Ed. 2011, 50, 10294-10317.
[2] Kawamoto, T.; Geib, S. J.; Curran, D. P. J. Am. Chem. Soc. 2015, 137, 8617-8622.
[3] Taniguchi, T.; Curran, D. P. Angew. Chem. Int. Ed. 2014, 53, 13150-13154.
[4] Nerkar, S.; Curran, D. P. Org. Lett. 2015, 17, 3394-3397.
39
OP20 - Additional Development to Functionalized Alkyl- and
Alkenylboronic Derivatives via Hydrodroboration
Thomas Cole
Department of Chemistry & Biochemistry
San Diego State University
San Diego, California 92182-1030 USA
Boronic derivatives have become one of the most important classes of reagents for
synthetic organic chemistry. These compounds are used extensively in the SuzukiMiyaura and Chan-Lam coupling reactions. The majority of 6,000 commercially available
boronic compounds are based on aromatic and heteroaromatic groups. In contrast, the
number of functionalized alkyl- and alkenylboronic compounds is far more limited. The
synthesis of more “natural product” like compounds for drug discovery will require
functionalized alkyl- and alkenylboronic compounds to become a more versatile and
essential reagent for organic synthesis.
Recently, we have reported a new route to the preparation of functionalized primary
potassium alkyltrifluoroborates.
This method relies on the unique selectivity of
dicyclohexylborane in the hydroboration of terminal alkenes over reduction of most all
functional groups. The mixed organoborane, Cy2BR, undergoes a two-group reductive
alkylation, selectively transferring the two secondary cyclohexyl groups to quinone, forming
the functionalized alkylboronic ester. The addition of potassium hydrogen difluoride
converts the boronic ester into the corresponding potassium alkyltrifluoroborate, permitting
easy isolation and purification. The isolated yields for this four-step one-pot reaction are
good to excellent. We have extended the scope of this reaction to the hydroboration of
functionalized terminal alkynes. Hydroborations of terminal alkynes are also faster than
reduction of functional groups. Vinylboronic derivatives are isolated as the corresponding
trifluroborate salts.
We have also examined the preparation of alkyl- and
alkenylphosphonate trifluoroborates from the corresponding unsaturated phosphonates.
These compounds are isolated as ionic liquids in contrast to the majority of trifluoroborates.
This route represents the first general method to prepare functionalized potassium 1alkenyl- and primary alkyltrifluoroborate using the well-established hydroboration
methodology, expanding the scope of these important reagents.
O
R'2 BH +
RFG
R'2 B
RFG
2
O
KHF2
H2 O
40
+
-
K F3 B
RFG
OP21 - Heteroaromatic Boronic Acids in Aqueous-Organic Media
Guy Lloyd-Jones,* Paul Cox, Jorge Gonzalez and Andrew Leach
School of Chemistry
University of Edinburgh
Edinburgh, EH9 3FJ, UK
Boronic acids are key reagents in synthesis[1] and ubiquitous in classic processes such as, inter
alia, Suzuki-Miyaura, oxidative Heck, Chan-Evans-Lam, and Liebeskind-Srogl coupling, and
addition to enones, carbonyls and imines. Boronic acid decomposition, notably by in situ
protodeboronation, compromises reaction efficiency. Methods to mitigate decomposition[2] include
highly tuned catalysts, additives (e.g. Cu, Zn and Ag salts) masked reagents and slow release from
MIDA boronates[3] and trifluoroborates.
General mechanistic understanding of direct aqueous protodeboronation has previously been
limited to substituted phenylboronic acids.[4] Kuivila determined kinetics for protodeboronation of
ArB(OH)2 in hot aqueous buffer (90 °C; pH 1.0-6.7) by UV-Vis spectroscopy at low concentrations,
and proposed two mechanisms to account for the net protodeboronation. Much more recently,
highly electron deficient 2,6-disubstituted ArB(OH)2 systems were independently studied by Perrin,
Cammidge[4b] and Buchwald,[4c] and a dianionic mechanism proposed.[4e] Considering the core
role of heteroaromatic boronic acids in synthesis and discovery, and the propensity for some to
undergo protodeboronation, during storage[4f] and in coupling, the lack of comparative kinetic data
is surprising. The presentation will focus on the mechanism of release of heteroaromatic boronic
acids from MIDA reservoirs,[3] and the pH-dependence of the intrinsic rates of aqueous
protodeboronation of the boronic acids. We will show that pH-rate profiles can be simulated using a
general model that has allowed a range of new mechanisms and side processes to be identified.
pKaH
pKa
pKaH
k3
pKa
k3
k2
(k3)
log k
k2
stability
in acid
stability
in acid
(k3)
pH
k1
(k3)
log k
Bibliography
[1] Hall, D, (Ed); Boronic acids: preparation and applications in organic synthesis, medicine and
materials (vols 1 and 2), Second
edition,
2011, pp 1-133, Wiley VCH, Weineheim, Germany.
variable
stability
variable stability
k5 2010, 50, 664-674; (b) Lennox, A. J. J.; Lloydacross G.
entire
across entire
[2] (a) Lennox, A. kJ.5 J.; Lloyd-Jones,
C. Isr. J. Chem.
pH range
pH range
Jones, G. C. Chem. Soc. Rev. 2014,
43, 412-443.
k2
k2 A. S.;kBurke,
1 k4
[3] Li, J.; Grillo,
M. D. Acc. Chem. Res.
2015, 48, 2297–2307.
[4]
(a)
Kuivila,
H.
G.;
Reuwer,
J.
F.;
Mangravite,
J.
A. J. Am. Chem. Soc. 1964, 86, 2666-2670; (and
k
3
k3
references therein) (b) Cammidge, A. N.; Crepy, K. V. L. J. Org. Chem. 2003, 68, 6832-6835.; (c)
Kinzel, T.; Zhang, Y.; Buchwald, S. L. J. Am. Chem. Soc. 2010,
(d) Lozada,
J.; Liu, (k5)
(k4)
pH 132,(k14073-14075
3)
(k3) 79, 5365-5368; (e)
(k4)Noonan,
(k5) A. G. Org. Biomol.
pHChem. 2014,
Z.; Perrin, D. M. J. Org.
G.; Leach,
Chem.
2015, 13, 2555-2560.
k2cat
greater stability
in neutral
pH region
log k
k1 k4
pH
(k3)
k1
k2
k2cat
greater stability
in neutral
pH region
(k2cat)
41 k2
(k2cat)
pH
pH
OP22 - New Frontiers in Preparation and Coupling of Chiral Boronates
for the Synthesis of Bioactive Heterocycles
Dennis G. Hall,* You-Ri Kim, Taras Rybak, Samantha Kwok
University of Alberta
Edmonton, AB, T6G 2G2, Canada
The last decade has seen great advances in the development of methods for the
preparation of chiral optically enriched organoboronates, which can serve as versatile
precursors of various enantioenriched products. Our laboratory has developed methods to
prepare functionalized, acyclic and cyclic secondary alkyl- and allyl-boronates through
catalytic enantioselective processes such as [4+2] cycloadditions, allylic substitutions,
conjugate additions, and a unique borylative isomerization of alkenyl triflates [1]. One
remaining challenge in the chemistry of alkylboronates is their cross-coupling, especially
with control of stereoselectivity. With this perspective, one of our initial approaches
featured the first enantioselective preparation of optically enriched 1,1-diboronyl
derivatives, which can be coupled chemo- and stereoselectively with a variety of aryl and
alkenyl halides under Pd catalysis [2]. A logical evolution of this concept is the
enantioselective desymmetrization via mono cross-coupling of prochiral, pinacol 1,1diboronates [3]. Recently, we optimized the stereospecific (>95:5 e.r.) Suzuki-Miyaura
cross-coupling of heterocyclic allylic boronates [4]. This sp3–sp2 bond-forming strategy
provides important 2- or 4-substituted pyran and piperidine products by way of a ligandcontrolled regiodivergent mechanism. The required substrates, heterocyclic allylic
boronates, were prepared by a novel catalytic enantioselective borylative isomerization of
enol perfluorosulfonates. Optimization of conditions for this borylation reaction along with
mechanistic studies led to a multigram-scale process effective under a low catalyst loading
using green, industrially attractive solvents. All of these methods can be applied to the
synthesis of complex heterocyclic natural products and pharmaceutical drugs.
Allylic substitutions
cross-coupling
H B(OR) 2
Conjugate additions
R 3Br
R1 * R 2
Cycloadditions
X = O, N
X
Isomerizations
H R3
R1 * R 2
X
F
HO
OH
Bpin
O
O
X
N
H
N
H
O
O
Ph
(+)-paroxetine
O
Ph
diospongin B
N
CF 3
CF 3
mefloquine
Bibliography
[1] D. G. Hall, J. C. H. Lee, J. Ding, Pure & Applied Chemistry 2012, 84, 2263-2277.
[2] J. C. H. Lee, R. McDonald, D. G. Hall, Nature Chemistry 2011, 3, 894-899.
[3] H.-Y. Sun, K. Kubota, D. G. Hall, Chem. Eur. J. 2015, 21, 19186-19194.
[4] J. Ding, T. Rybak, D. G. Hall, Nature Communications 2014, 5, 5474.
42
DP1 - CAAC: An Ideal Ligand for Stabilizing Highly Reactive LowValent Boron Species
Dr. Merle Arrowsmith, Dominic Auerhammer, Prof. Dr. Holger
Braunschweig*
Institut für Anorganische Chemie
Am Hubland, 97074 Würzburg
Since their introduction in 2005 cyclic alkyl(amino)carbenes (CAACs)[1] have proven
highly versatile ligands for the stabilization of unusual low-valent or radical main group
compounds[2], owing to their unique electronic σ-donating and π-accepting properties. In
the field of boron chemistry, for example, CAAC ligands have enabled the isolation of a
highly reactive diboracumulene species[3], three-coordinate boron(II) radicals[4] and the
first parent borylene[5].
In this contribution we report the synthesis of novel three-coordinate bis(carbene)
borylenes, [(CAAC)(L)BX] (L = CAAC, NHC; X = H, Cl, Br) via a simple one-pot reduction,
as well as the isolation of the first stable dihaloboron radicals, [(CAAC)BX2]●. Furthermore,
taking advantage of the π-backbonding influence of cyano ligands on the acidity of boronbound hydrogens, we have isolated a stable three-coordinate boron anion, which, upon
salt metathesis enables facile access to otherwise challenging boron-element bonds.
Finally, reduction of [(CAAC)B(CN)Br2] cleanly yielded the first cyanoborylene tetramer
[(CAAC)B(CN)]4, whose remarkable 12-membered [BCN]4 ring structure remains stable in
solution.
Bibliography
[1] V. Lavallo, Y. Canac, C. Prasang, B. Donnadieu, G. Bertrand, Angew. Chem., Int. Ed.
2005, 44, 5705.
[2] M. Soleilhavoup, G. Bertrand, Acc. Chem. Res. 2015, 48, 256.
[3] J. Böhnke, H. Braunschweig, W. C. Ewing, C. Hörl, T. Kramer, I. Krummenacher, J. Mies,
A. Vargas, Angew. Chem. Int. Ed. 2014, 53, 9082.
[4] P. Bissinger, H. Braunschweig, A. Damme, I. Krummenacher, A. K. Phukan, K. Radacki,
S. Sugawara, Angew. Chem., Int. Ed. 2014, 53, 7360.
[5] R. Kinjo, B. Donnadieu, M. Ali Celik, G. Frenking, G. Bertrand, Science 2011, 333, 610.
43
OP23 - Selective reactions of carbohydrates using organoboron
catalysts and promoters
Mark S. Taylor
Toronto, ON, M5S 3H6, Canada
It has been known for more than a century that carbohydrates interact with boron
compounds [1]. Established applications of these interactions include the protection of diol
groups in carbohydrates through boronic ester formation [2], and the selective recognition
of sugars using boronic acid-based synthetic hosts [3]. My group is interested in using
organoboron compounds to trigger selective chemical transformations of sugar derivatives
[4]. Formation of a tetracoordinate organoboron complex of a sugar-derived diol results in
an increase in nucleophilicity that enables catalytic, regioselective acylation, sulfonylation,
alkylation and silylation reactions of pyranosides. By extending this concept to reactions of
sugar-based electrophiles, we achieved selective glycosylations in which both the stereoand the regiochemistry of the product were influenced by the organoboron catalyst. These
catalyst-controlled glycosylations have been used to rapidly access complex,
carbohydrate-containing targets. More recently, we have begun to explore how changes in
solubility or pyranoside/furanoside ratio induced by binding of organoboron compounds to
sugars can be used to facilitate useful chemical reactions. It is becoming increasingly clear
that the superficially simple interactions of boron compounds with sugars can be used in
diverse ways to facilitate carbohydrate chemistry.
Bibliography
[1] E. Fischer, Ber. Dtsch. Chem. Ges. 1894, 27, 3189.
[2] R. J. Ferrier, Adv. Carbohydr. Chem. Biochem. 1978, 35, 31.
[3] R. Nishiyabu, Y. Kubo, T. D. James, J. S. Fossey, Chem. Commun. 2011, 47, 1106.
[4] M. S. Taylor, Acc. Chem Res. 2015, 48, 295.
44
OP24 - Generation of N→B-Ladders via Regioselective Hydroboration
F. Pammer,* M. Grandl, Y. Sun
Institute of Organic Chemistry II and Advanced Materials
University of Ulm
Albert-Einstein-Allee 11, 89081 Ulm/D
Boron containing π-conjugated organic materials have attracted growing interest in recent
years, due to their unusual optical and electronic properties.[1] Our focus in this field is the
development of preparative methods for the facile introduction of Lewis-acidic tricoordinate boron centers into conjugated oligo- and polymers composed of electrondeficient N-heterocycles. When a suitable regiostructure is formed this then gives rise to
ladder structure via intramolecular N→B-coordination. The molecular geometry and
electronic properties of the resulting conjugated systems are strongly affected by this
interaction, which generally leads to a planarization of the π-system and concurrent
extended conjugation, and increased electron affinity. Furthermore, this structural motive
has been shown to be a versatile precursor to access fully conjugated boron containing
heteroacenes.[2] However, research into these kinds of structures remains challenging,
since most preparative methods rarely allow to simultaneously introduce multiple N→Bgroups.
We have recently reported on the unusual regioselectivity of 1-alkenyl-substituted
pyridines in hydroboration reactions,[3] and were able to take advantage of this reactivity to
generate N→B-ladderized oligomers through two-fold regioselective hydroboration of a
suitable substrate (see Scheme).[4]
In this talk we report on the effect of borylation on the molecular structure and electronic
properties of the depicted oligopyridines, and discuss our latest efforts towards employing
electronically varied boranes and alternative substrates.
Bibliography
[1] C. D. Entwistle, T. B. Marder, Chem. Mater. 2004, 16, 4574.
[2] S. Wang, D.-T. Yang, J. Lu, H. Shimogawa, S. Gong, X. Wang, S. K. Mellerup, A.
Wakamiya, Y.-L. Chang, C. Yang, Z.-H. Lu, Angew. Chem., 2015, 127, 15289; Angew.
Chem., Int. Ed. 2015, 54, 15074.
[3] M. Grandl, F. Pammer, Macromol. Chem. Phys. 2015, 216, 2249.
[4] M. Grandl, F. Pammer, Chem. Eur. J., 2016, in print, DOI: 10.1002/chem.201600228.
45
OP25 - Iron(III) Imido Radical Complexes of a Diborate Tetrapodal
Pentadentate Ligand Framework
Warren Piers,*a Denis Spasyuk,a Laurent Maron,b Christos
Kefalidis,b Michael Neidig,c Stephanie Carpenterc
a
Department of Chemistry, University of Calgary
b
LPCNO, Université de Toulouse, INSA
c
Department of Chemistry, University of Rochester
Tetrapodal pentadentate ligands can be used to provide a defined platform for small
molecule activation and catalysis. One successful ligand design is the polypyridyl PY5
system first reported by the Stack[1] and Feringa[2] groups. This neutral ligand
coordinates to metals from across the periodic table and its oxidative stability allows
access to a range of metal oxidation states, a key feature for applications in catalysis.[3]
More recently, Gardinier has introduced a related ligand system, Pz4Py, incorporating
pyrazolyl donors instead of pyridyl moieties.[4]
The overall neutral charge of the PY5 and Pz4Py ligands necessarily means that higher
oxidation state intermediates bear positive charges and are fleeting, highly reactive
species. Rendering ligands anionic may stabilize higher oxidation state intermediates so
they can be studied in more detail. Dianionic renditions of these ligands should allow for
the synthesis of neutral higher oxidation state compounds; the transposition of carbon for
boron at the linking positions of the PY5 or Pz4Py ligands is an established way to
introduce the negative charges in the form of borates.[5] Here, we introduce the new
dianionic ligand B2Pz4Py and its use in the synthesis of iron imido complexes that are
strong hydrogen atom acceptors.
MeO
L
n
L
NN
MII N N
E
N
n
N N MII N N
NN
NN
N
E
E
H
H
E
OMe
PY 5
Pz 4Py
E = C, n = 2: dicationic complexes
E = B, n = 0: neutral complexes : B 2Pz 4Py
Bibliography
[1] Jonas, R. T.; Stack, T. D. P., J. Am. Chem. Soc. 1997, 119, 8566-8567.
[2] E. de Vries, M.; M. La Crois, R.; Roelfes, G.; Kooijman, H.; L. Spek, A.; Hage, R.; L. Feringa, B.,
Chem. Comm. 1997, 1549-1550.
[3] Zee, D. Z.; Chantarojsiri, T.; Long, J. R.; Chang, C. J., Acc. Chem. Res. 2015, 48, 2027-2036.
[4] Morin, T. J.; Bennett, B.; Lindeman, S. V.; Gardinier, J. R., Inorg. Chem. 2008, 47, 7468-7470.
[5] Trofimenko, S., Scorpionates: The Coordination Chemistry of Polypyrazolylborate Ligands.
Imperial College Press: London, 1999.
46
OP26 - B–H and P–H activation steps in phopshine–borane
dehydropolymerization: What you see is not what you first get.
Thomas N Hooper,a Nicholas A. Beattie,b Stuart A. Macgregor,b
and Andrew S. Weller*a
a
Department of Chemistry, University of Oxford, Mansfield Road,
Oxford, UK. OX1 3TA
b
Institute of Chemical Sciences, Heriot Watt University, Edinburgh,
EH14 4AS, UK
The polymerization of alkenes using transition metal–based catalysts to afford societally and
technologically ubiquitous polyolefins is well-established, yet equivalent catalytic routes to
polymeric materials containing main-group elements is considerably less developed. In
particular, the group 13/15 mixed polymers provide one example that promises to lead to
significant scientific and technological opportunities, given that polyphosphino-boranes, along
with polyamino-boranes, are (valence) isoelectronic with polyolefins and are finding uses in a
variety of applications from lithography to pre-ceramics.[1] Transition–metal catalysts have been
shown to promote dehydropolymerization of phosphine boranes;[1b] for example a recent report
of the use of the FeCp(CO)2(OTf) system by Manners and co–workers has demonstrated
impressive control over the molecular weight of isolated polymer.[2] However, the nature of the
actual catalyst and the order of events for B–H and P–H activation necessary for
dehydrocoupling have not been fully delineated. In part this is due to the relatively high
temperatures required for turnover in catalysis (melt conditions or 100ºC in toluene).
Dehydropolymerization
Manners
This work
[BArF 4]
[Rh] cat.
H 2BPRH
– H2
melt conditions or 100ºC
H 3BPRH 2
n
OC
Fe
C
O
Rh
OTf
Me 3P
Cl
Me
Cl
This contribution will present evidence for the delineation of the elementary B–H/P–H activation
processes occurring in phosphine–borane dehydrocoupling, via a combined experimental and
computational approach, when using [RhCp*Me(PMe3)(CH2Cl2)][BArF4] as a precatalyst. As
this complex provides a latent vacant site through CH2Cl2 dissociation, as well as a methyl
group that is well set up for loss of methane, the study of bond activation processes at ambient
temperature under solution conditions seemed a possibility. In particular the order of B–H/P–H
activation has been determined in these systems, as well as subsequent isomerisation and P–
B bond forming events. This provides insight into both the order of events and the likely
intermediates involved in dehydropolymerization of phosphine-boranes.[3]
Bibliography
[1]
(a) E. M. Leitao, T. Jurca and I. Manners, Nat. Chem. 2013, 5, 817; (b) H. C. Johnson, T. N.
Hooper and A. S. Weller Topics Organomet. Chem. 2015, 49, 153
[2]
A. Schäfer, T. Jurca, J. Turner, J. R. Vance, K. Lee, V. A. Du, M. F. Haddow, G. R. Whittell
and I. Manners, Angew. Chem. Int. Ed. 2015, 54, 4836.
[3]
T. N. Hooper, A. S. Weller, N. A. Beattie and S. A. Macgregor Chem. Sci. 2016, 7, 2414
47
SP7 - Synthesis and Characterization of Boron-Nitrogen Containing
Antiaromatic s-Indacene Derivatives.
Matthew Morgan, Warren E. Piers*
University of Calgary, Calgary, AB, T2N 1N4, Canada
Incorporating heteroatoms into conjugated organic frameworks continually yields novel
compounds possessing interesting electrochemical and photophysical properties different
than all carbon analogues. In particular, the replacement of C=C bonds with B=N bonds in
organic compounds has become popular as the bonds are isosteric and isoelectronic,
meaning that the overall electron count of the compound will remain the same, yet the
insertion of a BN moiety creates a polar bond that can lead to new reactivity as well as
provide access to new synthetic routes to previously unattainable organic compounds.1,2
While there has been much progress on making BN containing hydrocarbons, specifically
1,2-azaborine derivatives, there are still very few tuneable, general synthetic pathways to
make large ring systems.3,4 A common synthetic pathway to boron containing heterocycles
is transmetallation of early metal or tin containing species with haloboranes, but
surprisingly this has not been explored for the synthesis of boron-nitrogen containing
systems. Utilizing well established zirconocene chemistry5 with nitrogen containing
aromatics it is possible to assemble from the ground up a complex framework containing
boron nitrogen bonds. In order to show the versatility of this work several BN containing
hydrocarbons have been synthesized, culminating in the synthesis of a derivative of the
difficult to isolate s-indacene moiety. This presentation will focus on the development of a
zirconocene mediated synthetic pathway to a variety of antiaromatic BN containing sindacene derivatives.
Bibliography
(1)
Bosdet, M. J. D.; Piers, W. E.; Sorensen, T. S.; Parvez, M. Angew. Chemie - Int. Ed. 2007,
46 (26), 4940.
(2)
Neue, B.; Araneda, J. F.; Piers, W. E.; Parvez, M. Angew. Chemie - Int. Ed. 2013, 52, 9966.
(3)
Campbell, P. G.; Marwitz, A. J. V; Liu, S.-Y. Y. Angew. Chemie Int. Ed. 2012, 51 (25), 6074.
(4)
Morgan, M. M.; Piers, W. Dalt. Trans. 2015, 5920.
(5)
Wu, F.; Jordan, R. F. Organometallics 2005, 24 (11), 2688.
48
OP27 - Asymmetric Organoborane Conversions via the Amazing 9Borabicyclo[3.3.2]decanes
John A. Soderquist
University of Puerto Rico
San Juan, PR, 00931 USA
The stereoselective addition of reagents containing the chiral 10-substituted-9borabicyclo[3.3.2]decane (BBD) moiety to aldehydes, ketones, aldimines and ketimines
will be described. The rigid and robust nature of these systems permits a wide variety of
organoborane conversions to not only be conducted in a highly
manner, but also, it facilitates the recovery of the
R
Z enantioselective
chiral borane by-product which can be recycled through simple
B
operations. Moreover, numerous chemical conversions can be
performed on these organoboranes providing remarkable new
reagents for organic synthesis.1-8 The origin of the observed
selectivities will be presented and discussed in terms of the compact
chiral reaction centers provided by the BBD systems.
Bibliography
1. González, A. Z.; Román, J. G.; Alicea, E.; Canales, E.; Soderquist, J. A. J. Am.
Chem. Soc., 2009, 131, 1269. DOI: 10.1021/ja808360z
2. Soto-Cairoli, B.; Soderquist, J. A. Org. Lett., 2009, 11, 401. DOI:
10.1021/ol802685e
3. Muňoz-Hernández, L.; Soderquist, J. A. Org. Lett., 2009, 11, 2571. DOI:
10.1021/ol900865y
4. González, J. R.; González, A. Z.; Soderquist, J. A. J. Am. Chem. Soc. 2009,
131, 9924. DOI: 10.1021/ja9047202.
5. Chiral Ligation for Boron and Aluminum in Stoichiometric Asymmetric Synthesis,
3.22, Soderquist, John A. In Comprehensive Chirality, H. Yamamoto, E. Carreira
(Eds.); Elsevier: Amsterdam, 2012; pp 691-739, DOI: 10.1016/B978-0-08-0951676.00322-0
6. (E)-2-Boryl-1,3-dienes from the 10-TMS-9-BBDs: Highly Selective Reagents for
the Asymmetric Synthesis of anti-α,β-Disubstituted-β-allenylamines from the
Allylboration of Aldimines, González, J. A.; Soderquist, J. A. Org. Lett., 2014, 16 (14),
pp 3840–3843, DOI: 10.1021/ol501892a
7. Highly Functionalized tertiary-Carbinols and Carbinamines from the Asymmetric γAlkoxyallylboration of Ketones and Ketimines with the Borabicyclodecanes, MuñozHernández, L.; Seda, L. A., Wang, B.; Soderquist, J. A. Org. Lett., 2014, 16, ASAP,
DOI: 10.1021/ol5019486.
8. Cyclohexenylboration
of
Aldehydes
and
Ketones
with
the
Borabicyclo[3.3.2]decanes (BBDs), González, E.; Muñoz-Hernández, L.; Alicea, E.;
Singaram, B.; Kabalka, G. W.; Soderquist, J. A. Org. Lett., 2015, 17, 4368. DOI:
10.1021/acs.orglett.5b02194
49
OP28 - HOCH2B(OH)2 and 2,5-Dihydroxy-1,4-dioxa-2,5-diborinane
Donald S. Matteson
Washington State University
Pullman, WA 99164-4630 USA
(α-Silyloxyalkyl)boronic esters are promising intermediates for asymmetric synthesis, but
efficient access to these compounds to date has required (α-hydroxyalkyl)boronic esters as
intermediates.1 A better understanding of (-hydroxyalkyl)boronic acid and ester chemistry is
needed for efficient handling of these compounds for synthetic purposes. Known examples of
(-hydroxyalkyl)boronic acids crystallize as dimeric half-esters,2,3 and I have previously
extracted isolated the pinanedioi ester of HOCH2B(OH)2 from aqueous solution, though all
other esters tried proved to be too water soluble.4 (Hydroxymethyl)boronic acid dimer, 2,5dihydroxy-1,4-dioxa-2,5-diborinane (1), is stable in air and was only a few percent degraded to
boric acid after more than a year of storage in an open flask, as indicated by 11B-NMR. In dilute
basic solutions in D2O, HOCH2B(OH)2 requires a few hours to degrade at 97 °C, and there is a
strong H/D isotope effect.4 However, it is extremely sensitive to aqueous base when solutions
are concentrated, and yields were poor or zero in the presence of formate, sulfite, and other
weak bases. The easiest way to obtain 1 seemed to be evaporation of the acidic solutions from
hydrolysis of (i-PrO)2BCH2Br in the hood, though even that caused some degradation. Tai
Cheng had neutralized the solution with ion exchange resin bicarbonate in a single experiment
50 years ago and claimed an 85% yield,2 but an attempted repetition netted zero. The vacuum
pump Cheng used would have frozen the aqueous solution during distillation. Freeze drying
proved to be the answer. The mechanistic explanation is that HOCH 2B(OH)2 is converted by
base mainly to HOCH2B(OH)3–, which is inert, and –OCH2B(OH)2 is required in order to form a
three-membered ring analogous to that in postulated intermediate 3. However, hydroxylation of
a boron atom in 1 is the major reaction with base, even pure water is basic enough, and the
hydroxylated intermediate 2 can open and close or perhaps undergo direct concerted
rearrangement to intermediate 3, which then can break the carbon–boron bond with the aid of
proton transfer from the solvent to open to hydrolytically labile 4 in an exothermic step.
1
2
(?)
3
4
Bibliography
[1] Singh, R. P.; Matteson, D. S., J. Org. Chem. 2000, 65, 6650-6653.
[2] Matteson, D. S.; Cheng, T. C., J. Organomet. Chem. 1966, 6, 100-101; J. Org. Chem. 1968,
33, 3055-3060.
[3] Matteson, D. S.; Schaumberg, G.D., J. Org. Chem. 1966, 31, 726-731.
[4] Matteson, D. S., Aust. J. Chem. 2011, 64, 1425-1429.
50
OP29 - Ruthenium-Promoted Reduction of CO to Tetraborylmethane
and Hexaborylethane and NHC-Mediated Cleavage of B-B Bonds
Todd B. Marder
Institute of Inorganic Chemistry
Organoboranes are an important class of compound with applications ranging from optical
and electronic materials,[1] to intermediates in organic synthesis.[2] This lecture will
highlight some of our recent and unusual observations involving the chemistry of
diborane(4) compounds. First, we report that the reaction of B2pin2 with Ru3(CO)12 yields a
series of very interesting Ru4 clusters[3] bearing one or two bridging CBpin moieties, as
well as fully borylated methane C(Bpin)4 and ethane C2(Bpin)6, all of which arise from
reduction of CO. Then we will discuss reactions of NHC’s with diborane(4) compounds,
starting with simple adduct formation[4,5] and leading to B-B bond cleavage and ring
expansion of the NHC.[5-7]
Bibliography
[1] C. D. Entwistle, T. B. Marder, Chem. Mater. 2004, 16, 4574; Angew. Chem. Int. Ed. Engl.,
2002, 41, 2927.
[2] I. A. I. Mkhalid, J. H. Barnard, T. B. Marder, J. M. Murphy, J. F. Hartwig, Chem. Rev.,
2010, 110, 890.
[3] A. S. Batsanov, J. A. Cabeza, M. G. Crestani, M. R. Fructos, P. Garcia-Alvarez, M. Gille,
Z. Lin, T. B. Marder, Angew. Chem. Int. Ed. 2016, 55, 4707.
[4] C. Kleeberg, A. G. Crawford, A. S. Batsanov, P. Hodgkinson, D. C. Apperley, M. S.
Cheung, Z. Lin, T. B. Marder, J. Org. Chem. 2012, 77, 785.
[5] S. Pietsch, U. Paul, I. R. Cade, M. J. Ingleson, U. Radius, T. B. Marder, Chem. Eur. J.
2015, 21, 9018.
[6] S. K. Bose, K. Fucke, L. Liu, P. G. Steel, T. B. Marder, Angew. Chem. Int. Ed. 2014, 53,
1799.
[7] S. Würtemberger-Pietsch, U. Radius, T. B. Marder, Dalton Trans. 2016, 45, 5880.
51
OP30 - Design and Synthesis of Functional Organoboron Materials with
Intramolecular B-N Coordination Bonds
Atsushi Wakamiya,* Hiroyuki Shimogawa, Yoshitaka Aramaki,
Osamu Yoshikawa, Takuhiro Taniguchi, Michihisa Murata,* Yasujiro
Murata*
Instgitute for Chemical Research
Kyoto University
Gokasyo, Uji, Kyoto, 611-0011 Japan
Boron has several characteristic structural and electronic features. The consequent
exploitation of these characteristic features of boron in the molecular design enables us to
produce sophisticated -functional materials with attractive photophysical and electronic
properties.[1] Concerning the Lewis acidity of boron, trivalent boron readily forms unique
complexes containing coordination bonds, upon combination with Lewis bases or
nucleophilic species. This complexation can be used for structural and electronic
modifications of -conjugated systems. For examples, we demonstrated that the formation
of intramolecular B-N coordination bonds, by introducing the boryl groups at appropriate
positions so that they form intramolecular B–N coordination compounds, not only constrain
the -conjugated skeleton in a coplanar fashion, but also perturb the electronic structure
thereby enhancing the electron-accepting ability by lowering the LUMO level.[2] By utilizing
the B-N coordination bond as a key scaffold, we designed and synthesized several
functional materials such as electron-transporting materials,[2–3] air-stable NIR dyes
and/or fluorophore,[4–5] and dyes for solar cells.[6] We also found that the exploitation of
the reversibility of the intramolecular B-N coordination bond formation enables us to
produce the material that shows thermochromic and mechanochromic phenomena.[7] In
this presentation, we will introduce our recent progress on the several boron-containing conjugated systems that exhibit unique properties owing to the intramolecular B-N
coordination bond formation.
Bibliography
[1] A. Wakamiya, S. Yamaguchi, Bull Chem. Soc. Jpn. (Award Account) 2015, 88, 1357.
[2] A. Wakamiya, T. Taniguchi, S. Yamaguchi, Angew. Chem. Int. Ed. 2006, 45, 3170.
[3] A. Job, A. Wakamiya, G. Kehr, G. Erker, S. Yamaguchi, Org. Lett. 2010, 12, 5470.
[4] A. Wakamiya, T. Murakami, S. Yamaguchi, Chem. Sci. 2013, 4, 1002.
[5] H. Shimogawa, A. Wakamiya, Y. Murata, to be submitted.
[6] A. Wakamiya, T. Taniguchi, Y. Murata, J. T. Dy, H. Segawa, WO2012121397.
[7] Y. Aramaki, O. Yoshikawa, H. Shimogawa, M. Murata, A. Wakamiya, Y. Murata, to be
submitted.
52
SP8 - Donor-Functionlized N,C-Organoboron Chelates: Exploring the
Impact of Substitution at Boron
Soren Mellerup, Kang Yuan, Suning Wang*
Boron-containing -systems have long been known to possess interesting and unique
properties compared to their all-carbon analogues.1 One pertinent example is the
photochromic behaviour of four coordinated N,C-organoboron chelates (Figure 1),2 which
our group has been exploring for a number of years. Aside from their potential applicability
as molecular switches,3 the adaptability of the boron center depending on its chelating
ligand framework is truly remarkable.4 Nonetheless, substitution of the R groups on boron
has been neglected over the course of our investigations, primarily due to various
synthetic challenges associated with the preparation of their requisite precursors. We
therefore set out to establish a simple and efficient route to N,C-organoboron chelates with
varying R groups on boron to study their behaviour upon exposure to UV light. This
presentation will focus on the preparation of such compounds, as well as discuss the
electronic influence of the R groups on these types of photochemical transformations.
h
h
References:
(1) Zhou, Z.; Wakamiya, A.; Kushida, T.; Yamaguchi, S. J. Am. Chem. Soc. 2012, 134,
4529.
(2) Rao, Y.L.; Amarne, H.; Chen, L.D.; Brown, M.L.; Mosey, N.J.; Wang, S. J. Am. Chem.
Soc. 2013, 135, 3407.
(3) Irie, M. Chem. Rev. 2000, 100, 1685.
(4) (a) Rao, Y.L.; Amarne, H.; Wang, S. Coord. Chem. Rev. 2012, 256, 759. (b) Rao, Y.L.;
Horl, C.; Braunschweig, H.; Wang, S. Angew. Chem. Int. Ed. 2014, 53, 9086.
53
OP31 - Organoboron Polymers as Supported Lewis Acids
and Bases
Frieder Jäkle
Rutgers University-Newark
Newark, NJ 07201, USA
Organoborane polymers have emerged as an important class of functional materials with
applications ranging from the detection of anions and biologically relevant species to selfhealing materials, organic electronic materials, supported reagents and catalysts.[1] This
presentation will describe the efficient preparation of borane polymers with unmatched
structural diversity. Recent work on the development of Lewis acidic borinic acid and
arylborane polymers, their self-assembly and applications as sensory and stimuliresponsive materials will be introduced.[2] We will also discuss hybrid materials that utilize
Lewis basic pyridylborate ligand architectures for the complexation of transition metal
complexes.[3]
Bibliography
1. Recent review: F. Jäkle, Top. Organomet. Chem. (Springer) 2015, 49, 297-325.
2. a) F. Cheng, E. M. Bonder, and F. Jäkle J. Am. Chem. Soc. 2013, 135, 17286-17289; b)
W. Wan, F. Cheng, and F. Jäkle, Angew. Chem. Int. Ed. 2014, 53, 8934-8938; b) F. Cheng,
W.-M. Wan, Y. Zhou, X.-L. Sun, E. M. Bonder, and F. Jäkle, Polym. Chem. 2015, 6, 46504656.
3. a) P. Shipman, C. Cui, P. Lupinska, R. A. Lalancette J. B. Sheridan, and F. Jäkle, ACS
Macro Lett. 2013, 2, 1056-1060; b) G. Pawar, E. M. Bonder, R. A. Lalancette, J. B.
Sheridan, and F. Jäkle, Macromolecules 2015, 48, 6508-6515.
54
OP32 - Fluorescent temperature probes based on triarylboron
compounds
Yi Li,*1 Shayu Li,2 Guoqiang Yang*2
1
Key Laboratory of Photochemical Conversion and Optoelectronic
Materials, Technical Institute of Physics and Chemistry,
Chinese Academy of Sciences, Beijing 100190, China
Beijing National Laboratory for Molecular Sciences,
2
Key Laboratory of Photochemistry, Institute of Chemistry,
Chinese Academy of Sciences, Beijing 100190, China
Temperature is one of the most frequently measured variables as it is a principal
thermodynamic property. In situ characterizations for temperature become continuing
trend in analysis and diagnostics fields because of their apparent advantages.
Luminescence-based temperature sensors have received more attention because of their
fast response, high spatial resolution, and safety of remote handling. In this presentation, a
series of triarylboron compounds with intramolecular charge transfer (ICT) property and
dual emissive states are reported. These compounds exhibit thermosensitive hue
transformation with high fluorescent quantum efficiency in a wide temperature range. The
good stability and unique luminescent properties of the triarylboron compounds make them
potential intrinsic luminescent materials, using as luminescent probes for the detection of
temperature in solution and solid polymers, as well as in cells.
Bibliography
[1] J. Feng, K. J. Tian, D. H. Hu, S. Q. Wang, S. Y. Li, Y. Zeng, Y. Li, G. Q. Yang, Angew.
Chem., Int. Ed. 2011, 50, 8072.
[2] J. Feng, Lei Xiong, S. Q. Wang, S. Y. Li, Y. Li G. Q Yang, Adv. Funct. Mater. 2013, 23,
340.
[3] J. Liu, X. D Guo, R. Hu, J. Xu, S. Q. Wang, S. Y. Li, Yi. Li, G. Q. Yang, Anal. Chem., 2015,
87, 3694.
[4] X. Liu, S. Y. Li, J. Feng, Y. Li., G. Q. Yang, Chem. Commun., 2014, 50, 2778.
55
SP9 - 3-Coordinate Boron -Acceptors in Water-Soluble Chromophores
for Live Cell Imaging
Stefanie Griesbeck, Zuolun Zhang, Tessa Lühmann,
Marcus Gutmann, Lorenz Meinel, Todd B. Marder*
Institut für Anorganische Chemie, Julius-Maximilians Universität Würzburg
Am Hubland, 97074 Würzburg, Germany
E-Mail: [email protected], [email protected]
Triarylboranes have attracted a huge amount of interest, due to their application in many
different fields, such as anion sensing, OLEDs and non-linear optical materials.[1] Over the
last few years, we have studied the use of dimesitylboron based acceptors (A) in twophoton absorption (TPA) chromophores. We designed dipolar, quadrupolar and octupolar
compounds with exceptional TPA cross sections and high fluorescence quantum yields.[2]
Furthermore, we reported structure-TPA cross section relationships for our quadrupolar A-A compounds.[3] Recently, we synthesized oligothiophene-BMes2 chromophores, with
significantly enhanced TPA cross sections of up to 1930 GM in the near-infrared region,
the “biological transparent window”.[4] This makes our chromophores potential candidates
for two-photon excited fluorescence (TPEF) microscopy of living cells or tissues. We
present herein the further functionalization of them with ammonium groups, an approach
pioneered by Gabbaï,[5] in order to achieve hydrophilicity and biocompatibility, and our
initial results of live cell imaging with this compounds.
Bibliography
[1] (a) C. D. Entwistle, T. B. Marder, Angew. Chem. Int. Ed. Engl., 2002, 41, 2927. (b) C. D.
Entwistle, T. B. Marder, Chem. Mater. 2004, 16, 4574.
[2] J. C. Collings, C. Katan, A. Beeby, D. Kaufmann, W.-Y. Wong, M. Blanchard-Desce, T. B.
Marder et al., Chem. Eur. J., 2009, 15, 198.
[3] (a) M. Charlot, L. Porrès, C. D. Entwistle, A. Beeby, T. B. Marder, M. Blanchard-Desce, Phys.
Chem. Chem. Phys., 2005, 7, 600. (b) C. D. Entwistle, J. C. Collings, A. Steffen, A. Beeby, A.
S. Batsanov, J. A. K. Howard, W.-Y. Wong, A. Boucekkine, J.-F. Halet, T. B. Marder et al., J.
Mater. Chem., 2009, 19, 7532.
[4] L. Ji, R. M. Edkins, A. Beeby, A. S. Batsanov, J. A. K. Howard, A. Boucekkine, Z. Liu, J.-F.
Halet, C. Katan, T. B. Marder et al., Chem. Eur. J., 2014, 20, 13618.
[5] C.-W. Chiu, Y. Kim, F. P. Gabbaï, JACS, 2009, 131, 60.
56
OP33 - CO2 insertion into the C-B bond of boronic esters
Trevor Janes, Yanxin Yang, Kimberly Osten, Maotong Xu, Adam
Pantaleo, Ellen Yan, Datong Song*
Davenport Chemical Research Laboratories
University of Toronto, Toronto, ON, M5S 3H6, Canada
The discovery of new reactivities of CO2 is important as it may lead to new ways to utilize
CO2 as a C1 feedstock for synthesis.[1] Known reactivity of CO2 includes coordination to
metal centres,[2] insertion into M–X bonds (where M is a metal center and X is an element,
most commonly H or C) [3-5] and adduct formation with a Lewis base (with or without the
assistance of a Lewis acid).[6-7] These fundamental reactivities have resulted in the
catalytic conversion of CO2 into a variety of reduced products. Our group has
demonstrated formal insertion of CO2 into the C–H bond of an actor diazafluorenyl ligand
supported by a spectator metal center and further elaborated this work to include
metal‐free insertions.[8] This presentation will focus on our recent discovery of CO2
insertion into C-B bonds and its potential relevance to catalytic hydroboration of CO2.[9]
Bibliography
[1] M. Aresta, Carbon Dioxide as Chemical Feedstock. Wiley‐VCH, Weinheim, 2010.
[2] J. Mascetti. “Metal Coordination of CO2” in Encyclopedia of Inorganic and Bioinorganic
Chemistry, Wiley, Chichester, 2014.
[3] X. Yin, J. R. Moss, Coord. Chem. Rev., 1999, 181, 27.
[4] S. P. Bew, Comprehensive Organic Functional Group Transformations II. 2005, 19‐125.
[5] M. Cokoja, C. Bruckmeier, B. Rieger, W. A. Herrmann, F. E. Kühn, Angew. Chem. Int. Ed., 2011,
50, 8510.
[6] J. L. Murphy, K. N. Robertson, R. A. Kemp, H. M. Tuononen, J. A. C. Clyburne, Chem. Commun.,
2015, 51, 3942.
[7] D. W. Stephan, G. Erker, Chem. Sci., 2014, 5, 2625‐2641.
[8] V. T. Annibale, D. Song, Chem. Commun., 2012, 48, 5416; V. T. Annibale, D. A. Dalessandro, D.
Song, J. Am. Chem.Soc., 2013, 135, 16175.
[9] Y. Yang, M. Xu, D. Song, Chem. Commun. 2015, 51, 11293; T. Janes, K. M. Osten, A. Pantaleo, E.
Yan, Y. Yang, D. Song, Chem. Commun. 2016, 52, 414
57
OP34 - New Tetra-coordinated Boron Complexes: Synthesis,
Characterization and Photophysical Properties
Krishnan Venkatasubbaiah,* Vanga Mukundam, Kunchala
Dhanunjayarao, Mamidala Ramesh
School of Chemical Sciences
National Institute of Science Education and Research (NISER)
Bhubaneswar – 751005, India
There have been growing interest in the development of hybrid organic-inorganic materials
for applications in field effect transistors, organic light emitting diodes, non-linear optic
materials, catalysis and sensors owing to their long-term stability and performance over
the individual counter parts. Among various types of hybrid organic-inorganic system
boron containing compounds (tri- and tetra coordinated) [1-3] have received much interest
in developing fluorescent sensors, organic light emitting diodes, non-linear optics etc.
Recently we made efforts in synthesizing new boron-containing complexes that of interest
in the development of OLEDS and sensors. In my presentation I will discuss our recent
efforts in the synthesis of new tetra-coordinated boron complexes [4-6].
Bibliography
[1 Y.-L. Rao, H. Amarne, S. Wang, Coord. Chem. Rev. 2012, 256, 759.
[2] C. R. Wade, A. E. J. Broomsgrove, S. Aldridge, F. P. Gabbaï, Chem. Rev. 2010, 110,
3958.
[3] C. D. Entwistle, T. B. Marder, Chem. Mater. 2004, 16, 4574.
[4] K. Dhanunjayarao, V. Mukundam, M. Ramesh, K. Venkatasubbaiah, Eur. J. Inorg. Chem.
2014, 539-545.
[5] V. Mukundam, K. Dhanunjayarao, C-N Chuang, D-Y Kang, M-K Leung, K-H Hsieh, K.
Venkatasubbaiah, Dalton Trans. 2015, 44, 10228 - 10236.
[6] V. Mukundam, K. Dhanunjayarao, K. Venkatasubbaiah. Unpublished results.
58
OP35 - New developments in the synthesis of industrial borates
David M. Schubert
Research & Innovation Department
U.S. Borax Inc., Rio Tinto
Greenwood Village, Colorado 80111 USA
Millions of tons of boron chemicals are utilized annually in energy production and
conservation, agriculture and the manufacture of a multitude of everyday products. The
vast majority of these boron compounds contain boron that is bonded exclusively to
oxygen. With the exceptions of boric acid and boric oxide, these industrial borates also
contain cations which play important roles in their applications.
Borate chemistry features a remarkable tendency towards self-assembly of simple boron
species into complex polyborate structures containing rings, cages, chains, sheets or
networks. This assembly process involves the condensation of hydroxyborate species
guided by the coordination demands of metal cations and by hydrogen bonding
interactions. The presence of protic non-metal cations can further direct both covalent and
supramolecular structure. One goal of our work is to acquire a detailed understanding of
these factors and how they can be exploited to control borate architectures in order to
produce useful new materials.
Most new borate compounds reported by other groups in recent years have resulted from
experiments in which mixtures of reagents are heated under hydrothermal conditions in
pressure vessels for many days. These methods also generally involve formation of
byproducts. While this approach can provide crystals of previously undescribed
compounds, it does little to advance systematic methodologies needed for practical
industrial scale borate synthesis. In contrast, our approach focuses on the development of
rational syntheses carried out under non-hydrothermal conditions without the generation of
unwanted byproducts. Recent examples of such methods are presented, illustrating the
interplay between coordination chemistry, hydrogen bonding and borate architectures.
59
OP36 - Triple Decker Sandwich Complexes Containing Six Membered
Puckered and Planar Ring
Sundargopal Ghosh
Department of Chemistry,
Indian Institute of Technology Madras,
Chennai 600036, India
Having one valence electron less than carbon, boron is known to build mainly cage substructures. [1] Thus, compounds containing flat ring made of boron are very rare and only a
handful of such compounds are known. [2] Recently, we have isolated various tripledecker sandwich complexes containing puckered to flat middle rings, composed of boron
and non-boron elements. [3] Although, various theoretical studies have predicted that
triple-decker complexes with 30-34 valence electrons would show stability, our complexes
show lower valence electron counts. [4] For example, 1-5 (see picture below) with 22-24valence electrons represent lowest electron count triple-decker complexes. 6-8, on the
other hand, contain 30-valence electrons with a planar [B2S4] ring. The key results of this
work will be described.
Bibliography
[1] a) N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann,
Oxford, 1997; b) Fehlner, T. P.; Halet, J. F.; Saillard, J. Y. Molecular Clusters: A Bridge to Solid State
Chemistry; Cambridge University Press, 2007.
[2] a) R. N. Grimes, J. Organomet. Chem., 2013, 747, 4; b) S. Ghosh, A. M. Beatty, T. P. Fehlner, J.
Am. Chem. Soc., 2001, 123, 9188; c) B. P. T. Fokwa and M. Hermus, Angew. Chem. Int. Ed., 2012,
51, 1702; d) A. N. Alexandrova, A. I. Boldyrev, H. J. Zhai and L. S. Wang, Coord. Chem. Rev., 2006,
250, 2811; e) W. -L. Li, L. Xie, T. Jian, C. Romanescu, X. Huang and L. -S. Wang, Angew. Chem. Int.
Ed., 2014, 53, 1288.
[3] a) A. Thakur, K. K. V. Chakrahari, B. Mondal, S. Ghosh, Inorg. Chem., 2013, 52, 2262; b) B.
Mondal, B. Mondal, K. Pal, B. Varghese, S. Ghosh, Chem. Commun, 2015, 51, 3828.
[4] a) J. W. Lauher, M. Elian, R. H. Summerville and R. Hoffmann, J. Am. Chem. Soc., 1976, 98, 3219;
b) E. D. Jemmis, A. C. Reddy, J. Am. Chem. Soc., 1990, 112, 722; c) E. D. Jemmis and A. C. Reddy,
Organometallics, 1988, 7, 1561.
60
SP10 - Molecular Materials Based on Boron Complexes of Formazanate
Ligands
Stephanie M. Barbon, Ryan R. Maar, Samantha Novoa and Joe B.
Gilroy*
Department of Chemistry and the Centre for Advanced Materials and
Biomaterials Research
The University of Western Ontario
London, ON, N6A 5B7, Canada
E-mail: [email protected], [email protected]
Organic fluorescent dyes have received significant interest due to their remarkable optical
and electronic properties, as well as their tunable properties. Boron difluoride complexes of
chelating nitrogen-donor ligands make up a significant portion of this field, as they typically
exhibit high fluorescence quantum yields, excellent molar absorptivities
and interesting redox properties. We have synthesized a new class of
boron difluoride complexes based on formazanate ligands. Formazans are
easily synthesized from inexpensive starting materials, and the BF2 moiety
is introduced in one high-yielding step. The structures of the complexes (1)
are relatively planar, easily modified offering substituent-dependent optical
and electronic properties, and exhibit quantum yields up to 77%.1
The synthesis and characterization of these compounds will be presented,
and the effects of extended π-conjugation and electronwithdrawing/donating substituents on the properties of this new class of dyes will be
discussed.2,3 The study of the applications of these complexes, including their
electrochemiluminescence,4 use as fluorescent cell imaging agents,5 and incorporation into
polymers will also be highlighted.6
20 m
Bibliography
[1] S. M. Barbon, P. A. Reinkeluers, J. T. Price, V. N. Staroverov, J. B. Gilroy, Chem. Eur. J. 2014, 20,
11340-11344.
[2] S. M. Barbon, J. T. Price, P. A. Reinkeluers, J. B. Gilroy, Inorg. Chem. 2014, 53, 10585-10593.
[3] S. M. Barbon, V. N. Staroverov, J. B. Gilroy, J. Org. Chem. 2015, 80, 5226-5235.
[4] M. Hesari, S. M. Barbon, V. N. Staroverov, Z. Ding, J. B. Gilroy, Chem. Commun. 2015, 51, 37663769.
[5] R. R. Maar, S. M. Barbon, N. Sharma, H. Groom, L. G. Luyt, J. B. Gilroy, Chem. Eur. J. 2015, 21,
15589-15599.
[6] S. Novoa, J. A. Paquette, S. M. Barbon, R. R. Maar, J. B. Gilroy, J. Mater. Chem. C. 2016, DOI:
10.1039/C5TC03287C.
61
OP37 - Transition Metal Catalyzed Selective B-H Activation and
Functionalization of Carboranes
Zuowei Xie
The Chinese University of Hong Kong
Shatin NT, Hong Kong, China
Carboranes are a class of polyhedral boron hydride clusters in which one or more of the
BH vertices are replaced by CH units. They constitute a class of structurally unique
molecules with exceptionally thermal and chemical stabilities and the ability to hold various
substituents. These properties have made them useful basic units in supramolecular
design, medicine, catalysts and materials. However, their unique structures make
derivatization difficult, resulting in a limited application scope. Thus, it is important and
necessary to develop new methodologies for the functionalization of carboranes. Inspired
by transition metal catalyzed C-C/C-B bond forming reactions via benzene C-H activation
and our earlier work on transition metal mediated multicomponent cross-cycloaddition for
the preparation of benzocarboranes, we have developed transition metal catalyzed
regioselective direct cage B-H functionalization of o-carboranes. These results will be
discussed in this presentation.[1-5]
Bibliography
[1] Qiu, Z.; Ren, S.; Xie, Z. Acc. Chem. Res. 2011, 44, 299-309.
[2] Quan, Y.; Xie, Z. J. Am. Chem. Soc. 2014, 136, 15513-15516.
[3] Lyu, H.; Quan, Y.; Xie, Z. Angew. Chem. Int. Ed. 2015, 54, 10623-10626.
[4] Quan, Y.; Qiu, Z.; Xie, Z. J. Am. Chem. Soc. 2015, 137, 3502-3505.
[5] Quan, Y.; Xie, Z. Angew. Chem. Int. Ed. 2016, 55, 1295-1298.
62
OP38 - Polyarylboranes: A New and Diverse Class of Organic-Inorganic
Hybrid Materials Exhibiting High Photoluminescence Efficiencies.
Mark W. Lee Jr
University of Missouri
Columbia, Missouri, 65201, USA
Since the discovery of the dodecaborate [B12H12]2– ion nearly sixty years ago, [1] chemists
have sought new methods for its derivatization. [2, 3] Reports of polysubstitution (n>3) of
the dodecaborate ion have been limited to halogen, cyano, methyl, or hydroxyl groups (or
its derivatives).[4] Here, the author reports a new class of hybrid organic/inorganic
materials, polyarylboranes, where the dodecaborate core is surrounded by several (n=1 to
9) exohedrally bonded aromatic hydrocarbon substituents. Under surprisingly simple
conditions, employing mildly elevated temperatures and in the absence of any catalyst, the
dodecaborate ion quantitatively reacts directly with a large and diverse range of cyclic
aromatic hydrocarbons. Examples of molecules which are observed to react in this
manner include benzene, a wide range of substituted benzenes, polycyclic aromatic
hydrocarbons, and aromatic heterocycles. The electronic absorption and emission spectra
of these ions reveal the presence of strong –conjugation between the aryl substituents
and the dodecaborate core, resulting in high photoluminescence efficiencies. The solution
phase fluorescence quantum yields (F) of several derivatives were measured and are
remarkably high (as great as F >0.7 at room temperature). In every example, F was
greater than those of the substituents from which they were derived. This presentation will
focus on the syntheses of polyarylboranes, their electronic structures, and the extension of
this new chemistry to other polyhedral borane anions.
Bibliography
[1] A.R. Pitochelli, M. F. Hawthorne, J. Am. Chem. Soc. 1960, 82, 3228-9.
[2] W. Knoth, H. Miller, D. England, G. Parshall, E. Muetterties, J. Am. Chem. Soc. 1961, 82,
1056.
[3] I. Sivaev, V. Bregadze, S. Sjoberg, Collect. Czech. Chem. Commun. 2002, 67, 679-727.
[4] O. Farha, R. Julius, M. Lee, R. Huertas, C. Knobler, M. F. Hawthorne,2005, 127, 1824351.
63
OP39 - Aggregation-induced emission of diarylamino-π-carborane
triads: effects of charge transfer and π-conjugation
Yang-Jin Cho, So-Yoen Kim, Minji Cho, Won-Sik Han, Ho-Jin Son, Dae Won Cho,
Sang Ook Kang*
Korea University
Sejong-ro 2511, Sejong-city 30019, KOREA
Carborane-based donor-π-acceptor triads (D-π-A-π-D) bearing triarylamine moieties were
synthesized. All the monomeric triads showed a blue-green emission in a diluted solution,
which was assigned as an intramolecular charge-transfer (ICT) emission. The ICT
emission showed large Stokes shifts at a higher solvent polarity. The ICT emission further
shifted to a longer wavelength with the increase in π-conjugation. Interestingly, a strong
red emission was observed in highly concentrated solution or in the solid state, which was
assigned as an aggregation-induced emission (AIE). Moreover, the AIE strongly depended
on solvent polarity. A large ‘Stokes shift’ in AIE was attributed to the strong CT character.
The changes in the dipole moment for the AIE state and monomer emission were
evaluated using the ‘Lippert-Mataga’ relationship. The density functional theory
calculations showed that the change in electron distribution between the aryl amino group
(HOMO, HOMO) and the carborane moiety (LUMO, LUMO) indicates the ICT character,
and the emission color changes were attributed to the HOMO-LUMO energy gap
controlled by the π-extension of the phenylene linker. The electrochemical properties such
as oxidation and reduction potentials were consistent with theoretical calculation results.
The emission properties were affected by two main factors: solvent polarity and solubility.
Bibliography
[1] Seungjun Yi, Woo-Ri Bae, Jin-Hyoung Kim, Ah-Rang Lee, Woo-Young Kim, Won-Sik Han, HoJin Son, Sang Ook Kang, J. Mater. Chem. C, 2016, DOI: 10.1039/C6TC00017G.
[2] Seungjun Yi, Jin-Hyoung Kim, Yang-Jin Cho, Jiwon Lee, Tae-Sup Choi, Dae Won Cho,
Chyongjin Pac, Won-Sik Han, Ho-Jin Son, Sang Ook Kang, Inorg. Chem. 2016, 55, 3324-3331.
[3] Yang-Jin Cho, So-Yoen Kim, Minji Cho, Won-Sik Han, Ho-Jin Son, Dae Won Cho, Sang Ook
Kang, Phys. Chem. Chem. Phys. 2016, 18, 9702-9708.
64
OP40 - Toward the Development of Rhenacarborane Complexes as
CNS Drug Delivery Agents
Daniel G. Pruitt,a Kristin Bullock,b William A. Banksb and Paul A.
Jellissa,*
a, Department of Chemistry, Saint Louis University, St Louis, Missouri
63103, USA.
b, Department Internal Medicine, University of Washington, Seattle,
Washington, USA.
The search for non-invasive neural therapeutics is a problematic pursuit often hindered by
the blood-brain barrier (BBB), a gatekeeper of endothelial cells and tight junctions closely
regulating exchange between the bloodstream and brain tissue. A recent study of the
complex
[3-NO-3,3-2-(2,2'-N2C10H6(Me){(CH2)7131I}-4,4')-closo-3,1,2-ReC2B9H11]
(1)
(Figure 1) demonstrated its ability to not only safely pass through the BBB but also cleanly
efflux out of neural tissue, suggesting potential use as a drug-delivery vehicle for Central
Nervous System (CNS) infiltration [1]. However, due to the practical difficulty of
asymmetric modification of the bipyridyl ligand, a more direct synthetic approach of
carborane cage vertex adaptation has been investigated with the hope of utilizing such
species for CNS therapeutics [2]. A second prototype of [3,3-(CO)2-3-NO-closo-Re(8O(CH2)2O(CH2)2131I-3,1,2-C2B9H10)] (2) (Figure 1) was rapidly absorbed into the
bloodstream from the subcutaneous site of injection and displayed a 1 %Inj/g for peak
brain uptake, which rapidly stabilized to 0.1 while the previous complex 1 merely peaked at
0.1 %Inj/g. It was also determined that peak brain uptake of 15 ml/g was higher than lung
and liver tissues, suggesting that the brain is somehow specifically targeted, while the
exact rationale for selectivity remains to be explored.
Figure 1.
References
[1]. P. Hawkins, N. Nonaka, W.A. Banks, P.A. Jelliss, and X. Shi, J. Pharmacol. Exp. Ther.,
2009, 329, 608-614.
[2]. D.G. Pruitt, S.M. Baumann, G.J. Place, A.N. Oyeamalu, E. Sinn, and P.A. Jelliss, J.
Organomet. Chem., 2015, 798, 60-69.
65
SP11 - Reactivity of Boron–Boron Multiple Bonds
Julian Böhnke, Holger Braunschweig,* Theresa Dellermann, Kai
Hammond
The utilization of cyclic (alkyl)(amino)carbenes (CAACs) to stabilize the highly reactive B2 unit
led to the formation of a diboracumulene (C=B=B=C), in contrast to the discrete B–B triple
bond observed with NHC donors (C-BB-C).[1,2] The capacity of the CAAC ligands to
withdraw π-electron density from the B–B bond has provided access to a range of unique
bonding situations, which in turn provide information about the influence of the carbene.
Reactivity studies on this system led to base adducts (isonitriles, NHCs),[3] activation of small
molecules (CO, CO2, H2)[4] and cycloadditons with formation of archetypal aromatic species
(acetylene, propyne), illustrating the synthetic potential of multiple bonds featuring boron. 1,2addition of a dichalcogen reagent to the (NHC-stabilized) diboryne led to a diborene, whereas
the reaction with the (CAAC-stabilized) diboracumulene forms an isolable and roomtemperature stable 1,2-diradical.
Bibliography
[1] H. Braunschweig, R. D. Dewhurst, K. Hammond, J. Mies, K. Radacki, A. Vargas,
Science, 2012, 336, 1420−1422.
[2] J. Böhnke, H. Braunschweig, W. C. Ewing, C. Hörl, T. Kramer, I. Krummenacher, J.
Mies, A. Vargas, Angew. Chem. Int. Ed. 2014, 53, 9082–9085.
[3] J. Böhnke, H. Braunschweig, T. Dellermann, W. C. Ewing, T. Kramer, I. Krummenacher,
A. Vargas, Angew. Chem. Int. Ed. 2015, 54, 4469–4473.
[4] J. Böhnke, H. Braunschweig, T. Dellermann, W. C. Ewing, K. Hammond, T. Kramer, J.
O. C. Jimenez-Halla, J. Mies, Angew. Chem. Int. Ed. 2015, 54, 13801–13805.
66
OP41 - Boron Cluster Chromophores and Photosensitizers
Alexander M. Spokoyny
University of California, Los Angeles
Los Angeles, CA 90095
Website: www.organomimetic.com
This presentation will focus on our recent efforts in using organomimetic icosahedral boron
clusters as tunable building blocks for molecules and materials capable of interacting with
light. Importantly, I will highlight several extreme modalities that these clusters can serve in
creating chromophores and photosensitizers that have no analogues in classical
organic/organometallic chemistry.
Normally, unfunctionalized boron-rich clusters containing B-H bonds do not absorb light in
the visible region and also cannot undergo well-defined redox processes. In the first part of
this presentation I will focus on carboranes, which in their unfunctionalized form exhibit
extremely large HOMO-LUMO gap (> 10 eV). This property recently allowed us to create a
new class of chelating photophysically innocent ligand scaffolds providing a new avenue
for rationally designing organic light-emitting diode (OLED) materials.
Perfunctionalization of B-H vertices can lead to a pronounced reduction in the HOMOLUMO gap in the resulting cluster species producing unique photoredox properties. In the
second half of this presentation, I will highlight our newly discovered visible light
photoredox behavior of B12(OR)12 clusters which can interact with olefinic species and
subsequently initiate their polymerization. Specifically, I will show that this process occurs
across a wide array of both electron-rich and electron-deficient styrene monomers as well
as isobutylene.
67
OP42 - Reactivity of Novel Carboryne Precursor
Zaozao Qiu
Shanghai-Hong Kong Joint Laboratory in Chemical Synthesis
Shanghai Institute of Organic Chemistry
Chinese Academy of Sciences
345 Lingling Road, Shanghai 200032, China
1,2-Dehydro-o-carborane (o-carboryne) was first reported in 1990 by Jones as a very
reactive intermediate, which can be viewed as a three-dimensional relative of benzyne.[1]
It has demonstrated a rich reaction chemistry such as [4+2]/[2+2] cycloaddition, ene
reaction and C–H bond insertion reaction with a variety of organic molecules to give a
large series of o-carborane derivatives.[2] We synthesized a novel precursor 1-OTf-1,2C2B10H11 and found it can react with arenes and heteroarenes in much higher efficiency
than other known carboryne precursors. On the other hand, treatment of 1-OTf-1,2C2B10H11 with lithium primary and secondary amides gave a series of N-carboranyl amines
in moderate to high isolated yields with a broad substrate scope.[3] Mechanistic studies
suggest that the o-carboryne intermediate is involved in this amination reaction on the
basis of experimental results and DFT calculations. This represents the first general
method for the synthesis of 1-R1R2N-o-carboranes, which have potential use in medicinal
and materials chemistry.
Bibliography
[1] H. L. Gingrich, T. Ghosh, Q. Huang, M. Jones, Jr., J. Am. Chem. Soc. 1990, 112, 4082.
[2] D. Zhao, Z. Xie, Coord. Chem. Rev. 2015, DOI: 10.1016/j.ccr.2015.07.011.
[3] R. Cheng, J. Zhang, J. Zhang, Z. Qiu, Z. Xie, Angew. Chem. Int. Ed. 2016, 55, 1751
68
OP43 - Target Synthesis Boron/Nitrogen-Alkane Analogs
Xuenian Chen,* Jin Wang, Ximeng Chen, Ruirui Wang, Congchao
Cui, Xiaoge Feng
School of Chemistry and Chemical Engineering, Henan Key Laboratory
of Boron Chemistry and Advanced Energy Materials
Henan Normal University
Xingxiang, Henan, 453007, China
Email: [email protected],
Materials containing boron/nitrogen have attracted more attention because of their unique
properties such as super hardness and good abrasivity. However, in comparison with
thsousands of alkanes which can be used to prepare carbon materials, a very few B,Nalkane analogs, which can be used to make B/N mateials, have been synthesized. On the
basis of the Isolobal Analogy, B-N and C-C are iso-electronic so B,N-alkane analogs
should have a similar framework as alkanes and be generally occurred.
On the other hand, the different electronegativity of boron from nitrogen leads B,N-alkane
analogs to be polar molecules and hydrogens bonding to boron and nitrogen atoms are
chemical active, which results in totally different properties of B,N-alkane analogs from that
of alkanes. For example, ethane is a non-polar molecule and its melting point is -184˚C,
but its isolectronic B,N-alkane analogs, ammonia borane, NH3BH3, is a polar molecule with
the M.P. 103˚ C. The polarity and activity of B,N-alkane analogs mentioned above make
their preparation difficult. As a result, only a few B,N-alkane analogs such as
NH3(BH2NH2)nBH3，(n = 0,1,2) were prepared, and in most case, these compounds were
serendipitously prepared. We found such B.N-alkane analogs can be terget synthesized
using proper reactions. In this topic, we report the target synthesis of B,N-alkane analogs.
We will also discuss the influence factors and mechanism of reactions and try to
summarize the general synthetic methods for preparation of long chain B,N-alkane
analogs
[NH2 BH2 NH2BH3] -
NH3 BH2 NH2BH3
Bibliography
[1] Chen, X.; Bao, X.; Billet, B.; Shore, S. G.;Zhao, J.-C.,Chem. Eur. J., 2012, 18, 11994
[2] Chen, X.; Bao, X.; Zhao, J.-C.; Shore, S. G., J. Am. Chem. Soc., 2011, 133, 14172.
[3] Lingam, H. K.; Chen, X.; Zhao, J.-C.; Shore, S. G. Chem. Eur. J. 2012, 18, 3490.
[4] Daly, S. R.; Bellott, B. J.; Kim, D. Y.; Girolami, S., J. Am. Chem. Soc., 2010, 132, 7254.
[6] Li, H.; Ma, N.; Meng, W.; Judith, G.; Qiu, Y.; Li, S.; Zhao, Q.; Zhang, J.; Zhao, J.-C.; Chen,
X., J. Am. Chem. Soc. 2015, 137, 12406.
69
OP44 - Boron Containing Retinoids as Potential Therapeutics for
Spinal Cord Injury
Bhaskar C. Das,*1 Mrinmay Chakrabarti,2 and Swapan K. Ray2
1
Department of Medicine, The University of Kansas Medical Center, KS 66205, USA
2
University of South Carolina School of Medicine, Department of Pathology, Microbiology,
and Immunology, Columbia, SC, USA, Email: [email protected]
The long-term goal of our program is to develop boron containing biology oriented small molecule libraries and
use these compounds as new neurotherapeutic agents for the treatment of neurodegenerative injuries and
diseases. We are exploiting the recent appreciation that boron containing pharmacophore groups interact with
a target protein not only through hydrogen bonds but also through covalent bonds to produce potent biological
activity [1].
Spinal cord injury (SCI) is a serious and complex neurotrauma that is affecting 10,000 to 12,000 patients every
year in the United States. The only approved therapy for SCI is methylprednisolone (MP), which shows limited
efficacy and its use in SCI remains controversial [2]. So, new therapeutic approaches targeting SCI must be
developed for protecting neurons and preserving spinal cord function. All-trans retinoic acid (ATRA) has been
shown to be a therapeutic agent for reducing pro-inflammatory cytokine expression, augmenting autophagy,
and inhibiting apoptosis [3]. Unfortunately treatments based on the natural retionoid ATRA and synthetic
retinoids have so far not proven effective and are also burdened with high toxicity. To address these issues,
our research program is based on an underlying concept to design and synthesize receptor subtype and
isotype specific compounds using our Limited Rational Design approach [3,4]. In other words, retinoids with
receptor selectivity restricted to specific RAR or RXR subtypes may be effective, safer, and may be adopted
as potential neurotherapeutics for the treatment of SCI and neurodegenerative diseases modulated by RA
pathways.
We have synthesized and characterized new boron containing retinoic acids or bororetinoids for
neuroprotection using VSC4.1 motoneurons exposed to 200 nM calcium ionophore (CI) as the cell culture
model of SCI. The synthetic bororetinoid compound BIT-5 showed the least cytotoxicity than ATRA and other
related compounds in VSC4.1 motoneurons and also BIT-5 showed significantly higher neuroprotection than
any other compounds in VSC4.1 cells pre-exposed to 200 nM CI and also BIT-5 (Fig. 1, left). Our RT-PCR
and Western blotting analysis indicated that BIT-5 upregulated the expression of RARα not RARβ (Fig. 1,
Right). Manipulation of microRNAs (miRs) might be another approach to combat detrimental consequences in
SCI [5]. Our qRT-PCR analysis showed that CI treatment inhibited expression of many neuroprotective miRs
like miR-34a, miR-138, miR-184, miR96, miR-98, and miR-133b with time. We observed most drastic change
in expression of miR-96 in the CI insulted VSC4.1 cells. Also, our in vitro SCI results clearly indicated that
inflammatory and apoptosis molecules were activated after the CI insult in VSC4.1 cells and combination of
BIT-5 and miR-96 could effectively provide neuroprotection through enhancement of autophagy and inhibition
of apoptosis. In this talk, I will discuss in details the synthetic strategy of our lead molecule BIT5, and its
biological effect as potential neuroprotective agent and the future directions. Fig. 1.
Bibliography
[1] Das B.C. et.al. Future Med. Chem. 2013, 5, 653
[2] Lidal IB.et.al. Spinal Cord. 2008, 46:710-715, 2008.
[3] Das, B.C. et.al. PLoS One. 2010, 5(4), e10004
[4] Das, B.C. et.al. Bioorg. Med. Chem. 2014, 22: 673-683.
[5] Yunta M.et.al. PLoS One. 2012, 7:e34534.
70
SP12 - Transition Metal Diborane Complexes: An Experimental and
Quantum Chemical Study
Bijan Mondal, V. Ramkumar, Sundargopal Ghosh*
Over the past few decades transition metal complexes of boron have developed as the
fourth class of compounds made up by direct metal-boron interactions. Given the interest
to the chemistry of diboranes, recent years have witnessed substantial growth in this area
due to their bonding and significant applications in catalysis. [1] The structures of
hydrogen-substituted diboron compounds, B2H6, B2H4, and B2H2 have been continuously
studied for the complete understanding of chemical bonding. [2] Despite ubiquitous ability
of diborane to adopt 3c–2e bonding, complexes where a metal binds to B2 unit of any kind
are particularly rare. [3] Of late, various monometallic transition-metal diborane complexes
were reported and up till now, only handful of bimetallic/trimetallic-diborane complexes is
known, where the diboranes act as a bridge between the metal atoms. [4] This
presentation will focus on our recent synthetic and computational findings of the diborane
species stabilized in the coordination sphere of transition metals. [5]
Bibliography
[1] a) S. Aldridge, D. L. Coombs, Coord. Chem. Rev., 2004, 248, 535; b) L. Dang, Z. Lin, T. B. Marder,
Chem. Commun., 2009, 3987.
[2] a) W. N. Lipscomb, Acc. Chem. Res., 1973, 6, 257; b) A. Hübner, M. Bolte, H.-W. Lerner, M.
Wagner, Angew. Chem., Int. Ed., 2014, 53, 10408.
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132, 8258; b) H. Braunschweig, A. Damme, R. D. Dewhurst, A. Vargas, Nat. Chem., 2013, 5, 115.
[4] a) A. Wagner, E. Kaifer, H-J Himmel, Chem. Eur. J., 2013, 19, 7395; b) A. B. Chaplin, A. S. Weller,
Angew. Chem., Int. Ed., 2010, 49, 581; c) H. D. Kaesz, W. Fellmann, G. R. Wilkes, L. F. Dahl, J. Am.
Chem. Soc., 1965, 87, 2753.
[5] a) R. S. Anju, D. K. Roy, B. Mondal, K. Yuvaraj, C. Arivazhagan, K. Saha, B. Varghese, S. Ghosh,
Angew. Chem., Int. Ed., 2014, 53, 2873; b) D. Sharmila, B. Mondal, R. Ramalakshmi, S. kundu, B.
Varghese and S. Ghosh, Chem. Eur. J., 2015, 21, 5074.
71
DP2 - Ferrocene-Based Planar Chiral Lewis Pair Systems
Alain C. Tagne Kuate, Jiawei Chen, Roger A. Lalancette, Frieder Jaekle*
Rutgers University – Newark
Chemistry Department
73 Warren Street, Newark, NJ 07102, USA
Email: [email protected], Fax: +1 973 353 1264
Since the initial breakthroughs on the reactivity of unquenched Lewis acids and bases, a
new era in materials chemistry and catalysis has opened and offered to scientists a large
spectrum of potential applications. Accordingly, small molecule fixation, bond activation,
and the development of transition metal-free catalysts have been among the many
attractions of Lewis pair chemistries.[1] Owing to the great importance of asymmetric
synthesis in organic transformations, Lewis pairs incorporating chirality have naturally
emerged and the most recent findings include the chiral intra- and intermolecular amineand phosphine-borane Lewis pairs 1 and 2.[2,3]
Ferrocene represents an ideal and attractive ligand support for the attachment of Lewis
pairs at its edge with the possibility to fine-tune the Lewis acidity by redox chemistry and to
investigate the response in reactivity. We and others have recently introduced planar chiral
ferrocene-based Lewis pairs, 3 [4] and 4 [5], that establish an equilibrium between the
open and the closed form in solution. In this contribution, we wish to present our recent
work in this field including the development of new planar-chiral ferrocene-based Lewis
pair systems such as 5 [6] and 6.
Bibliography:
[1]
D. W. Stephan, G. Erker, Angew. Chem. Int. Ed. 2015, 54, 2.
[2]
M, Lindqvist, K. Borre, K. Axenov, B. Kόtai, M. Nieger, M. Leskela, I. Pápai, T.
Repo, J. Am. Chem. Soc. 2015, 137, 4038.
[3]
S. Wei, H. Du, J. Am. Chem. Soc. 2014, 136, 12261.
[4]
X. Wang, G. Kehr, C. G. Daniliuc, G. Erker, J. Am. Chem. Soc. 2014, 136, 3293.
[5]
J. Chen, R. A. Lalancette, F. Jäkle, Chem. Eur. J. 2014, 20, 9120.
[6]
a) J. Chen, D. A. Murillo Parra, R. A. Lalancette, F. Jäkle, Angew. Chem. Int. Ed.
2015, 54, 10202 ; b) J. Chen, A. C. Tagne Kuate, R. A. Lalancette, F. Jäkle,
Organometallics 2016, submitted.
72
OP45 - Palladium-catalyzed Coupling Reactions of Iodododecaborates
Joel Dopke,* Dorothy Buening, Kristen Westdorp, Richard Staples[1],
Alejandro Ramirez[2]
Alma College
Alma, MI, 48801, United States
Since its first reported synthesis by Hawthorne, et al., over 50 years ago [3], the
icosahedral dodecaborate B12H122– and its derivatives have garnered interest in a broad
range of applications—ranging from catalysis to nuclear medicine—due to their low
nucleophilicities, high thermal and kinetic stabilities, and low toxicities [4]. These
properties naturally led to the need for harsh reagents and forcing reaction conditions,
often resulting in poor reproducibility, in the derivatization of B12H122- [5]. Reproducible
pathways utilizing mild conditions for the substitution of dodecaborates could introduce
new structural motifs, provide access to sensitive functionalities, and result in even
broader applications of these cluster species.
Recent work in our labs has focused on the application of the easily-accessible
iodododecaborate dianion B12H11I2– to palladium-catalyzed coupling chemistry. This
presentation will focus on the application of the cluster dianion in reaction schemes
utilizing terminal alkenes H2CCHR (R = C6H5 (1), CONH2 (2), COCH3 (3), COOCH3 (4), CN
(5)) and microwave heating to provide cluster-appended olefins [6]. The product yields
range from nearly quantitative (1,2) to ~40% (5) as assessed by 11B NMR spectroscopy.
The product cluster anions were characterized by 11B, 1H, and 13C NMR, ESI-MS, and Xray crystallography, and are stable indefinitely in the solid state. The regiochemistry of
alkene substitution will be discussed.
B
B
B
B
I
B
B
B
B
B
B
2–
B
+
B
Pd 0, Base
CH3CN, MW
B
B
2–
B
B
B
B
B
B
B
B
B
B
Bibliography
[1] Michigan State University, Department of Chemistry, East Lansing, MI, 48824.
[2] Baylor University, Department of Chemistry and Biochemistry, Waco, TX, 76798.
[3] Hawthorne, M. F., Pitochelli, A. R., J. Am. Chem. Soc. 1960, 82, 3228.
[4] Sivaev, I. B., Bregadze, V. I., Sjöberg, S. Collect. Czech. Chem. Commun. 2002, 679.
[5] Knoth, W.H.; Sauer, J.C.; Balthis, J.H.; Miller, H.C.; Muetterties, E.L. J. Am. Chem. Soc.
1967, 89, 4842.
[6] Patel, P.A.; Ziegler C.B.; Cortese, N.A.; Plevyak, J.E.; Zebovitz, T.C.; Terpko, M.; Heck,
R.F. J. Org. Chem. 1977, 42, 3903.
73
POSTER PRESENTATION ABSTRACTS
74
PP1 - Synthesis, chemical characterization, in silico studies and
potential applications of fructo-borates.
Antonio Abad-García, Ana L. Ocampo-Néstor, Cynthia ReyesLópez, José G. Trujillo-Ferrara, Marvin A. Soriano-Ursúa*
Department of Physiology, Escuela Superior de Medicina-IPN
Mexico City, 11340, Mexico
Email: [email protected]; [email protected]
Boronic acids (as Phenylboronic acid, PBA) have been studied by our workgroup in regard
of a pair of attractive features, their behavior in specific pH, temperature, environment and
solvent conditions as well as the particular reaction with hydroxyl groups. The latter
condition is found in some carbohydrates such glucose or fructose. Particularly, it is known
that PBA reacts with carbohydrates forming a stable strong, reversible and covalent type
of bond, but just a few data are related to facilitation of reaction or stability of adducts.
Therefore, we explore the synthesis of boron-carbohydrates adducts. We found a
regioselectivity reaction yielding bis(phenylboronate) structures, which are capable of
masking four hydroxyl groups of the hexoses in the most stable thermodynamic forms [1]
and in agreement to in silico simulations. Therefore, we obtained a fructo-boronate crystal
determined with the most accurate description of a diboronate ester of beta-D-fructose
characterized by spectroscopy analysis such IR, NMR and mass spectrometry. From X-ray
results, we observed a strong hydrogen bond in each hydrogen from de C19 generating
weak repellent interactions between them and the free hydroxyl group in the same Carbon
and due to the B centers show very little deviation from planarity [2]. In addition, we
observed that one equivalent of acetone is incorporated, with no significant intermolecular
association, that could help in the transitory formation of carbanions (when it is present in
the reaction acid substances) and electro-transference between the reactants [3].
The insights from the present work let us to propose technologies which can be applied to
design health devices, or innovative pharmaceutical forms as syrup [2]. The aims for their
applications are multiple, but two are especially attractive for us, the inferred ability of
these compounds to act as carbohydrate sensors in vivo [2], and the high potential to act
as enzyme inhibitors on key-enzymes of pathogenic microorganisms.
Bibliography
[1] E. Kaji, D. Yamamoto, Y. Shirai, et al. Eur. J. Org. Chem. 2014, 17, 3536.
[2] S.P. Draffin, P.J. Duggana, G.D. Fallona, Acta. Cryst. 2004, E60, o1520.
[3] S.G. Pyne, M. Tang. Org. React. 2014, 83, 1.
75
PP2 - Synthesis and Fundamental Properties of B-PhenyldibenzoBorepin and its Derivatives
Naoki Ando, Tomokatsu Kushida, Shigehiro Yamaguchi*
Graduate School of Science and
Institute of Transformative Bio-Molecules (ITbM)
Nagoya University
Furo, Chikusa, Nagoya, 464-8602, Japan
Borepins, boron-containing seven-membered rings, are neutral and 6π aromatic systems
isoelectronic to a tropylium ion. Recently ring-fused borepins have attracted much
attention as boron-containing acene derivatives [1]. In these compounds, however, it is
necessary to introduce a bulky substituent on the boron atom to gain sufficient stability. On
the other hand, we have previously demonstrated that fixation of triarylborane skeletons in
a coplanar fashion is an effective strategy for stabilization of tricoordinate boron
compounds [2]. In this work, we have designed and synthesized planarized Bphenyldibenzoborepin 1, as a new family of planarized boron-containing π-electron
systems.
According to the previous method, compound 1 was synthesized by the intramolecular
Friedel-Crafts cyclization of di(2-isopropyl)phenyl-substituted precursor. This compound
showed high stability toward air and moisture. In addition, compound 1 maintained Lewis
acidity enough to form complexes not only with a fluoride ion, but also with weak Lewis
basic pyridine derivatives. These results indicate that compound 1 has higher Lewis acidity
than a planarized triphenylborane and trimesitylborane, which are both inert against
pyridine derivatives. In this presentation, photophysical properties of 1 and its derivatives
will also be discussed.
Bibliography
[1] a) L. G. Mercier, W. E. Piers, M. Parvez, Angew. Chem. Int. Ed. 2009, 48, 6108; b) A. Caruso
Jr., M. A. Siegler, J. D. Tovar, Angew. Chem. Int. Ed. 2010, 49, 4213; (c) A. Caruso Jr., J. D.
Tovar, J. Org. Chem., 2011, 76, 2227; d) D. R. Levine, A. Caruso Jr., M. A. Siegler, J. D. Tovar,
Chem. Commun. 2012, 48, 6256; e) A. Caruso Jr., J. D. Tovar, Org.Lett. 2011,13, 3106; f) D. R.
Levine, M. A. Siegler, J. D. Tovar, J. Am. Chem. Soc. 2014, 136, 7132.
[2] a) Z. Zhou, A. Wakamiya, T. Kushida, S. Yamaguchi, J. Am. Chem. Soc. 2012, 134, 4529; b)
S. Saito, K. Matsuo, S. Yamaguchi, J. Am. Chem. Soc. 2012, 134, 9130; c) C. Dou, S. Saito, K.
Matsuo, I. Hisaki, S. Yamaguchi, Angew. Chem. Int. Ed. 2012, 51, 12206.
76
PP3 - Poly(Aryl Ether) Based Borogels: A New Class of Materials for
Hosting Nanoparticles and Sensing Anions
C. Arivazhagan, Partha Malakar, Monojit Ghosal Chowdhury,
Edamana Prasad, Sundargopal Ghosh*
Indian Institute of Technology Madras
Chennai 600036 India
Supramolecular gels based on low molecular weight gelators (LMWGs) have attracted
widespread attention due to their potential applications in fields such as optoelectronic
devices, drug delivery, tissue engineering and sensors [1, 2]. Among the various of
dedrimers available, poly(aryl ether) dendron derivatives has been extensively studied due
to their optimum stability and flexibility [3-5]. Recently we have developed a facile
approach towards synthesis of boron containing poly(aryl ether) dendron based
supramolecular gels. The extensive 𝜋-𝜋, as well as H-bonding interactions, observed in
these molecules, facilitates the self-assembly process and imparts high stability.
Interestingly, one of the the poly (aryl ether) based borogel exhibits high viscoelasticity
than the known poly(aryl ether) dendron based gels, which signifies the presence of strong
intermolecular interactions through hydrogen bonding networks. The gel is successfully
utilized as a template for the in situ synthesis of well dispersed silver nanoparticles
(AgNPs) in hydrogel networks. In addition, solvent dependent sensing study of cyanide
(CN-) and fluoride (F-) is also accomplished by these supramolecular materials. In this
presentation the key results of this work will be described.
Bibliography
[1] A. R. Hirst, B. Escuder, J. F. Miravet, D. K. Smith, Angew Chem. Int. Ed. 2008, 47, 8002.
[2] a) N. M. Sangeetha, U. Maitra, Chem. Soc. Rev. 2005, 34, 821; b) P. K. Lekha, E. Prasad,
Chem. Eur. J. 2010, 16, 3699.
[3] N. V. Lakshmi, D. Mandal, S. Ghosh, E. Prasad, Chem. Eur. J. 2014, 20, 9002.
[4] Partha Malakar, Edamana Prasad, Chem. Eur. J. 2015, 21, 5093.
[5] S .D .Bull, M. G. Davidson, J. M. H. van den Elsen, J. S. Fossey, A. T. A. Jenkins, Y.-B.
Jiang, Y. Kubo, F. Marken, .K .Sakurai, J. Zhao, T. D. James, Acc. Chem. Res. 2013, 46,
312.
77
PP4 - Influence of substitution patterns on diborene
properties
Dominic Auerhammer, Holger Braunschweig*
Department of Inorganic Chemistry
Julius-Maximilians Universitaet Wuerzburg
97074 Wuerzburg, Germany
The synthesis of multiply bonded boron-boron species is a burgeoning research area.
Whereas homodiatomic multiple bonds of other p-block elements have been known for a
while, boron-boron multiple bonds had, until recently, received little attention. In 2007
Robinson and co-workers reported the first neutral diborene, obtained through the
reductive coupling of a NHC-stabilized BBr3 compound, albeit in poor yield.[1] In 2012 we
achieved the synthesis of another Lewis base-supported diborene via similar reductive
coupling, but this time with good reaction control thanks to the use of stabilizing aryl
ligands.[2] Over the following years we reported the synthesis of a number of other
diborenes as well as their reactivity toward a variety of substrates.[3] The derivatization of
one of these diborenes (1) constitutes the basis of this research project. The influence of
various aryl ligands and NHC bases on the positions of HOMOs and LUMOs was
assessed, as well as their bearing on reactivity. For this purpose a series of NHC-borane
adducts and their corresponding diborenes were synthesized, isolated and tested for their
properties.
Bibliography
[1]
Wang Y., Quillian B., Wei P., Wannere C. S., Xie Y., King R. B., Schaefer H. F., Schleyer P.
v. R., Robinson G. H. J. Am. Chem. Soc. 2007, 129, 12412.
[2]
P. Bissinger, H. Braunschweig, A. Damme, T. Kupfer, A. Vargas Angew. Chem. Int. Ed.
2012, 51, 9931–9934.
[3]
(a) H. Braunschweig, R. D. Dewhurst, K. Hammond, J. Mies, K. Radacki, A. Vargas,
Science 2012, 336, 1420–1422. (b) H. Braunschweig, A. Damme, R. D. Dewhurst, A.
Vargas, Nat. Chem. 2012, DOI: 10.1038/NCHEM.1520. (c) P. Bissinger, H. Braunschweig,
A. Damme, T. Kupfer, I. Krummenacher, A. Vargas Angew. Chem. Int. Ed. 2014, 53, 5689–
5693. (d) H. Braunschweig, R. D. Dewhurst, C. Hörl, A. K. Phukan, F. Pinzner, S. Ullrich
Angew. Chem. Int. Ed. 2014, 53, 3241–3244. (e) H. Braunschweig, T. Dellermann, W. C.
Ewing, T. Kramer, C. Schneider, S. Ullrich Angew. Chem. Int. Ed. 2015, 54, 10271–10275.
(f) J. Böhnke, H. Braunschweig, T. Dellermann, W. C. Ewing, T. Kramer, I. Krummenacher,
A. Vargas Angew. Chem. Int. Ed. 2015, 54, 4469–4473.
78
PP5 - Enhancement of Electron-Deficient Character of Organoboron
Macrocycles
Nurcan Baser-Kirazli, Frieder Jäkle*
Rutgers University-Newark,
73 Warren Street,
Newark, NJ 07102, USA
Conjugated macrocycles have attracted interest not only because of their cyclic structures
without any end group, but also the potential for use in catalysis, material science, chiral
sensing, supramolecular chemistry, self-assembly, and nanotechnology.1,2 In recent years,
the functionalization of conjugated systems with main group elements has been appealing
amongst scientists. Particularly, the incorporation of tricoordinate organoborane groups
into conjugated systems has attracted considerable attention due to the interaction
between the vacant p-orbital of boron and π-conjugated systems.3,4
Previously,
our
group
introduced the first example of
electron-deficient conjugated
organoboron macrocycles with
fluorene
bridges.5
The
objective of the current work is
to enhance the electronFigure 1
deficient character of the
prospective macrocycles and
to further explore their redox and optoelectronic properties. We have successfully
prepared the triboron building blocks B3-Mes* and B3-FMes with bulky supermesityl (Mes*)
and electron withdrawing fluoromesityl (FMes) groups attached to the central boron atom
(Figure 1). These compounds were fully characterized and an X-ray crystal structure of
B3-Mes* was acquired. Their utility as a building block for the preparation of macrocycles
was investigated.
Bibliography
[1] Kitsiou, C.; Hindes, J.J.; Unsworth, W.P. Angew. Chem. Int. Ed. 2015, 54, 15794-15798.
[2] Iyoda, M.; Rahman, M. Angew. Chem. Int. Ed. 2011, 50, 10522–10553.
[3] Yin, X.; Guo, F.; Lalancette, R.; Jäkle, F. Macromolecules 2016, 49, 537-546.
[4] Chen, P.; Yin, X.; Baser-Kirazli, N.; Jäkle, F. Angew. Chem. Int. Ed. 2015, 54, 1-6.
[5] Chen, P.; Jäkle, F. J. Am. Chem. Soc. 2011, 133, 20142.
79
PP6 - Carborane Passivated Aluminum Nanoparticles
Alexander Benziger, Michael West, Chiashin Chen, Blake
Hamman, Sophia Hayes, Steven Buckner, Paul Jelliss*
Saint Louis University
St. Louis, MO, 63110, USA
Aluminum nanoparticles have been synthesized and successfully passivated with an ocarborane cap. Previous studies have performed this process using epoxides and alkenes
to great success [1]. Aluminum nanoparticles have been studied for many potential energy
storage applications, such as potential fuel additives [2] or solid rocket fuels [3]. Boron
nanoparticles have been studied for similar applications in energetic as fuel additives [4].
Through passivating the nanoparticles with o-carborane, highly stable and energetic
material has been synthesized. This presentation will focus on the characterization of this
novel material. Powder X-Ray Diffraction has been used to confirm the synthesis of fcc
aluminum, and the presence of o-carborane. It is seen that over 24 hours, the o-carborane
peaks disappear from the pattern, however the aluminum stays, suggesting the
occurrence of some chemical reaction involving the carborane. Transmission electron
microscopy has been used in conjunction with scherrer analysis to determine particle
sizes. Nanoparticles have been destroyed in water, and the resulting solutions 11B{1H}
NMR have been studied. Solid State 11B NMR has also been performed on aged
nanoparticles, in an attempt to identify the unknown carborane.
Bibliography
1.
Thomas, B.J., et al., Polymerization Initiation by Electron-Rich Metal Nanoparticles
(PIERMEN). Journal of Materials Chemistry, 2013. 2014: p. 1-8.
2.
Mehta, R.N., et al., Study of stability and thermodynamic properties of water-indiesel nanoemulsion fuels with nano-Al additive. Appl. Nanosci., 2015. 5(8): p. 891900.
3.
Galfetti, L., et al., Nanoparticles for solid rocket propulsion. J. Phys.: Condens.
Matter, 2006. 18(33): p. S1991-S2005.
4.
E, X.-t.-f., et al., Jet fuel containing ligand-protecting energetic nanoparticles: A
case study of boron in JP-10. Chem. Eng. Sci., 2015. 129: p. 9-13.
80
PP7 - Novel Trinuclear Complexes of Group 6, 8 and 9 Metals with a
Triply Bridging Borylene Ligand
Moulika Bhattacharyya, Sundargopal Ghosh*
Chennai 600036
Email : [email protected], [email protected]
Free borylenes are highly reactive chemical entity unlike their isoelectronic complement
carbene and can only be obtained as transient species under drastic conditions [1]. Over
the past few decades, intense research efforts were concentrated on borylene complexes,
and many different coordination modes for ligand of the type BR have been established [2].
The synthesis and the chemistry of triply bridging borylene complexes of ruthenium were
established by Suzuki [3]. Recently, we have reported a series of homo and hetero
metallic triply bridging-borylene complexes that contain a “parent” borylene ligand
[4][5].During the course of our studies on heterometallic triply bridged borylene complexes,
we have recently isolated a series of novel trinuclear complexes of group 6, 8 and 9
transition metals with a µ3-BH ligand.The key results of this work will be discussed.
Bibliography
[1] H. Braunschweig, R. D. Dewhurst, A. Schneider, Chem. Rev. 2010, 110, 3924.
[2] a) H.Braunschweig, R. D. Dewhurst, V. H. Gessner, Chem. Soc. Rev. 2013, 42, 3197.
b) D. A. Addy, G. A. Pierce, D. Vidovic, D. Mallick, E. D. Jemmis, J. M. Goicoechea, S.
Aldridge,
J. Am. Chem. Soc. 2010, 132, 4586.
[3] R. Okamura, K. -I. Tada, K. Matsubara, M. Oshima, H. Suzuki, Organometallics 2001, 20,
4772.
[4] K. Geetharani, S. K. Bose, B. Varghese, S. Ghosh, Chem. Eur. J. 2010, 16, 11357.
[5] D. Sharmila, B. Mondal, R. Ramalakshmi, S. Kundu, B. Varghese S. Ghosh, Chem. Eur.
J. 2015, 21, 5074.
81
PP8 - Spontaneous Formation of a B-B Single Bond compound
Nicolas Bouchard, Etienne Rochette, Julien Légaré Lavergne, and Frédéric-Georges
Fontaine*
Département de chimie and Centre de recherche en Catalyse et Chimie Verte (C3V)
Université Laval
E-mail: [email protected]
The discovery of Frustrated Lewis Pairs (FLPs) by Stephan et al. lead to various examples
of metal-free small molecules activation by sterically hindered acid/base pairs1, 2. Recently,
our group reported a novel metal-free C-H borylation catalytic system for hetero-arenes,
using the FLP 2,2,6,6-tetramethylpiperidino-C6H4-BH2 as catalyst and HBpin as a
borylating agent3.
Despite being very little studied to date, Boron-boron bond containing molecules have
potential in formation of B-C bond and in the preparation of other interesting boron
containing materials4,5 . Herein, we report that FLP species can activate B-H bonds and
subsequently form B-B bonds through dehydrogenative pathway.
Synthesis and
characterization of new B-B bond containing compounds, kinetic analysis of the B-B bond
formation and DFT investigation of the mechanism will be discussed.
Bibliography
[2] Stephan, D. W.; Erker, G. FLP chemistry: Topics in Current Chemistry;
Eds.; Springer: New York, 2013; Vols, 332, and 334.
513-516.
[4]Wagner, A.; Litters, S.; Elias, J.; Kaifer, E.; Himmel, H. J. Chem. - A Eur. J. 2014,
12514.
[5] Schulenberg, N.; Ciobanu, O.; Kaifer, E.; Wadepohl, H.; Himmel, H. J. Eur. J. Inorg.
Chem. 2010, 2, 5201.
82
PP9 - In Pursuit of a Gallium-Carbon Double Bond
Jeremy L. Bourque, Kim M. Baines*
Western University
The study of the chemistry of unsaturated main group compounds, specifically those involving
double bonds of heavy Group 14 elements (M=E; M = Si, Ge; E = C, Si, Ge), has been of
much interest for many years. Silenes (Si=C) and germenes (Ge=C) have been shown to
activate a wide range of small molecules, including aldehydes, [1] alkynes [2] and
organometallic reagents. [3] Tetrelenes are reactive toward a wide range of substrates and
have been shown to be useful in the synthesis of unique inorganic compounds, in particular
ring systems. [4] Interestingly, although these silenes and germenes have been well-studied,
there are no reports in the literature describing the synthesis of a compound containing a
gallium-carbon double bond. The presence of a Lewis acidic gallium centre within a multiply
bonded system may lead to new and exciting reactivity reactivity. The synthetic route used in
an attempt to synthesize the first double bonded gallium-carbon compound will be described.
Bibliography
[1] C. J. Allan, C. R. W. Reinhold, L. C. Pavelka, K. M. Baines, Organometallics, 2011, 30,
3010-3017.
[2] N. Y. Tashkandi, L. C. Pavelka, M. A. Hanson, K. M. Baines, Can. J. Chem. 2014, 92,
462-470.
[3] B. Farhadpour, J. Guo, L. C. Pavelka, K. M. Baines, Organometallics, 2015, 34, 37483755.
[4] K. K. Milnes, L. C. Pavelka, K. M. Baines, Chem. Soc. Rev. 2016, 45, 1019-1035.
83
PP10 - Phenoxylation of chloro-boron subphthalocyanines: a rapid
axial functionalization method for a variety of nucleophiles
Esmeralda Bukuroshi, Dr. Timothy P. Bender*
Department of Chemical Engineering and Applied Chemistry
University of Toronto, 200 College Street, Toronto, ON, M5S 3E5, Canada
Email: [email protected]; * Corresponding: [email protected]
Boron subphthalocyanines (BsubPcs) have been incorporated into organic electronic
devices such as organic photovoltaics and organic light emitting diodes. Their physical and
electronic properties can be tuned via substitution of the peripheral hydrogens and axial
chloride. [1] The displacement of the labile axial halide in halo-BsubPcs has been limited
to reaction with oxygen- and carbon-based nucleophiles, involving lengthy reaction times
and elevated temperatures. [2] A process has been developed to react halo-BsubPcs (ClBsubPc and Br-BsubPc) with oxygen-, sulfur- and nitrogen-containing nucleophiles by
treatment with aluminum chloride under mild conditions. A detailed mechanism for this
process has been proposed and supported by experimental observation and NMR
spectroscopy (1H, 11B, and 27Al); it involves the formation of a stoichiometric complex
between a Cl-BsubPc and AlCl3. Phenol reacts with the aluminum atom in the complex
forming a new intermediate complex, rather than with the boron atom itself making this
reaction independent of the nature of the starting BsubPc (Cl-BsubPc, Br-BsubPc and
peripherally substituted BsubPc). The successful formation of novel thiophenoxy and
phenyl amino deriviatives of BsubPc was confirmed by X-ray crystallography and all
common analytics.[3] We have recently reopened this line of inquiry by exploring
alternative Lewis acids to AlCl3 including FeCl3, AlF3, BBr3, BCl3, SnCl4, SiCl4, AlCl3, InCl3,
and B(CF5)5. The results indicated that SnCl4 and B(CF5)5 yield the desired BsubPc
derivative at shorter time periods. These findings have lead us to further scope this
synthetic method with other BsubPcs, such as Cl-Cl6BsubPc and Cl-Cl12BsubPcs, as well
as a variety of oxygen, sulfur and nitrogen based nucleophiles. The goal is to reduce
reaction time, reduce heating requirements as well as access novel derivatives that
otherwise could not be obtained.
[1] G. E. Morse, M. G. Helander, J. Stanwick, J. M. Sauks, A. S. Paton, Z. H. Lu, T. P.
Bender, The Journal of Physical Chemistry C 2011, 115(23), 11709-11718.
[2] T. Fukuda, M. M. Olmstead, W. S. Durfee, N. Kobayashi, Chem. Commun. 2003, 12561257.
[3] G.E. Morse, T.P. Bender, Inorganic Chemistry 2012, 51(12), 6460-6467.
84
PP11 - N-Heterocycylic Carbene Stabilized Group 13 Compounds
Levy L. Cao, Erika Daley Jeffrey M. Farrell, Douglas W. Stephan*
80 St. George St., Toronto, ON, M5S 3H6, Canada
Since frustrated Lewis pair (FLP) chemistry has been reported, many stoichiometric and
catalytic reactivities have been revealed.[1] To continue exploring this area, new active
Lewis acids (LAs) must be discovered. (I): The Stephan group has reported a new protocol
for an effective synthesis of planar N-heterocyclic carbene (NHC) borenium ions (3), which
can be prepared from hydride abstraction of the carbene-borane adduct (1), followed by
heating.[2] One electron reduction of 3 gives an NMR active species 4 which can be
trapped by PhNO or TEMPO to give 5 and 6.[3] (II): the hydride abstraction reaction of the
carbene-alane adducts (7a & 7b) with trityl borate was also studied in different solvents,
with different cationic aluminum hydride complexes being obtained (8a & 8b).[4]
Bibliography
[1]
D. W. Stephan, Acc Chem Res 2015, 48, 306-316.
[2]
J. M. Farrell, D. W. Stephan, Angewandte Chemie 2015, 54, 5214-5217.
[3]
L. L. Cao, J. M. Farrell, D. W. Stephan, manuscript in preparation.
[4]
L. L. Cao, E. Daley, T. C. Johnstone, D. W. Stephan, Chemical Communications
2016, 52, 5305-5307.
85
PP12 - Supramolecular Functionalization of Boron Nitride Nanotubes
(BNNTs) with Conjugated Polymers
Fuyong Cheng, Yadienka Matinez-Rubi, Christa M. Homenick, Keun Su Kim,
Christopher T. Kingston, Benoit Simard
Security and Disruptive Technologies Portfolio
National Research Council Canada
100 Sussex Drive, Ottawa, ON, K1A 0R6, Canada.
E-mail: [email protected]
Boron nitride nanotubes (BNNTs) are isoelectronic to carbon nanotubes (CNTs), but they are
distinct in several aspects. BNNTs are wide band gap semiconductors regardless of the tube
diameter, chirality, or number of walls, and exhibit excellent mechanical, electronic, and thermal
properties; more specifically they are electrically insulating but thermally conducting. Similar to
CNTs, BNNTs can be produced by laser ablation, arc discharge, chemical vapor deposition, thermal
annealing, substitution reaction, and solid-state processing. Most of these synthesis methods
produce BNNTs in small quantities. Chemical functionalization of BNNTs is necessary to improve
processability and harness their full potential as high mechanical strength fibers, electrical insulators,
or thermally conducting materials. Herein, we will introduce a large-scale BNNT synthesis method
using a metal catalyst-free induction thermal plasma process.1 The resulting BNNTs are few-walled,
highly crystalline, and have an average diameter of 5 nm. We have extended our supramolecular
CNT functionalization approach2,3 to BNNTs using conjugated polymers, such as Zn-polyporphyrin
(Zn-PP), polyfluorene and polythiophene.4 This approach significantly enhanced the processability
of BNNTs through the formation of stable polymer/BNNTs complexes. Absorption spectroscopy was
used to confirm planarization and enhanced conjugation of the polymer to the BNNT surface by a
large red-shift (Figure 1). Combining our large-scale production method with our supramolecular
functionalization approach overcomes both the supply and processability challenges that have
limited BNNT’s potential.
Figure 1. A) Illustration of Zn-PP complexing BNNTs; B) absorption spectra of Zn-PP/BNNT
complexes with progressively increasing quantities of BNNTs.
[1] K. S. Kim, C. T. Kingston, A. Hrdina, M. B. Jakubinek, J. Guan, M. Plunkett, B. Simard, ACS Nano.
2014, 8, 6211-20.
[2] F. Cheng, A. Adronov, Chem. Eur. J. 2006, 12, 5053-5059.
[3] F. Cheng, P. Imin, C. Maunders, G. Botton, A. Adronov, Macromolecules 2008, 41, 2304-2308.
[4] Y. Matinez-Rubi, J. J. Jakubek, M. B. Jakubinek, K.S. Kim, F. Cheng, M. Couillard, C.T.
Kingston, B. Simard, J. Phys. Chem. C 2015, 119, 26605−26610.
86
PP13 - A Mild Hydrosilylation of Imines and Quinolines through
Carbene-stabilized Boro-cation Catalysis
Joshua Clarke, Brian Bestvater, Patrick Eisenberger, Cathleen Crudden*
Cationic boron-centered Lewis acids have emerged as interesting main group catalysts in
the activation of element-element bonds (H-H, B-H) resulting in net reduction of
unsaturated organic functional groups through Frustrated Lewis Pair (FLP) chemistry.[1-4]
Hydrosilylations of imines have been previously conducted with neutral perfluorinated
boron-centered Lewis acids.[5] Herein we report our recent investigations into mild
hydrosilylation of imines and quinolines via triazolylidene-based mesoionic carbenestabilized borenium ion catalysis. The exclusive 1,4-hydrosilylated dihydroquinoline
products can be subsequently telescoped in a C-C bond-forming reaction with an
electrophile to give unique cyclic amine structures.
[1] P. Eisenberger, B. P. Bestvater, E. C. Keske, C. M. Crudden, Angew. Chem. Int. Ed.
2015, 54, 2467
[2] P. Eisenberger, A. M. Bailey, C. M. Crudden J. Am. Chem. Soc. 2012, 134, 17384
[3] J. M. Farrell, J. A. Hatnean, D. W. Stephan, J. Am. Chem. Soc. 2012, 134,
15728−15731
[4] J. M. Farrell, R. T. Posaratnanathan, D. W. Stephan, Chem. Sci. 2015, 6, 2010-2015
[5] Blackwell, J. M., Sonmor, E. R., Scoccitti, T., Piers, W. E., Org. Lett., 2000, 2 (24),
3921-3923
87
PP14 - New Synthesis Pathway to Organoborane Phosphonates
Lauren Daley, Thomas Cole*, Khawlah Alanqari
San Diego, CA, USA
Organoboranes have grown to be an important class of coupling reagent with versatile
applications in small molecule biotechnology, “green” chemistry, and organic synthesis.
There are several routes to trifluoroborates including hydroboration [1], transmetallation [2],
catalyzed hydroboration [3], and borylation [4]. However, each method has respective
limitations from mild reactivity to expensive reagent costs. After discovering a keystone
step to boronic acids, two-group reductive alkylation, one of our principle research
interests has been to establish the scope of the reaction by using various starting alkenes
that have not been traditionally examined. One class of organoborane was found
particularly interesting was the phosphonate trifluoroborate which was isolated as an ionic
liquid. Much like other purified functionalized trifluoroborates made by two-group reductive
alkylation, these unique compounds are air-stable. In most instances, trifluoroborate salts
are white crystals easily purified by recrystalization but require subtle changes in the
purification mixture with different functional groups. However, properties of the
phosphonate functional group impeded normal isolation and required alternate procedures.
This new class of coupling reagent opens the door for our salts by expanding utility and
the types of coupling reactions that apply. Wittig and Horner-Emmons-Wadsworth
reactions are additional applications along with Suzuki and Chan-Lam [5]. This poster will
focus on our findings on the unusual properties of this new ionic liquid and several of its
applications.
Bibliography
[1] Brown, Herbert C, and S. K Gupta. Journal of the American Chemical Society, 97.18
(1975): 5249-5255.
[2] Molander, Gary A, and Deidre L Sandrock. ChemInform, 41.19 (2010).
[3] Yamamoto, Yasunori, Rhyou Fujikawa, Tomokazu Umemoto, and Norio Miyaura.
Tetrahedron, 60.47 (2004): 10695-10700.
[4] Yang, CT, ZQ Zhang, H Tajuddin, CC Wu, J Liang, JH Liu, Y Fu, M Czyzewska, PG
Steel, TB Marder, and L Liu. Angewandte Chemie-international Edition, 51.2 (2012):
528-532
[5] Umezawa, Taiki, Tomoya Seino, and Fuyuhiko Matsuda. Organic Letters, 14.16
(2012): 4206.
88
PP15 - Iron SNS complexes as efficient catalysts for selective
hydroboration of aldehydes and ammonia borane dehydrogenation
Uttam K. Das, Karine Ghostine, Bulat Gabidullin and R. Tom Baker*
Department of Chemistry and Biomolecular Sciences and
Centre for Catalysis Research and Innovation (CCRI)
University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
Iron complexes as catalysts are highly desirable because they are inexpensive, earth
abundant and non-toxic with respect to precious metal catalysts. Iron features not only a
broad spectrum of oxidation states and the ability to catalyze both reduction and oxidation
reactions but also has the ability to transfer one or two electrons to a substrate. Moreover, the
diversity of iron catalysts can be extended by introducing redox-active ligands which
participate cooperatively in catalytic processes [1, 2]. In our efforts to develop new
bifunctional iron catalysts, we have been investigating sterically svelte tridentate ligands
with a mixture of hard nitrogen and soft sulfur donors. Recently, we reported a series of
mono-, di- and trinuclear Fe(II) complexes containing an easily prepared tridentate thiolate
ligand with imine and thioether donors, [SMeNS-] [3]. During our on-going studies with this
ligand, we obtained a neutral imine-coupled Fe(II) complex, 1 (Scheme 1) which is an
efficient catalyst for selective hydroboration [4] of aldehydes with HBPin. Aldehyde
reduction occurs selectively in the presence of other reducible functional groups including
ketones, nitriles and alkenes. Furthermore, a cationic Fe(II) phosphine complex containing
this ligand was also shown to be active for ammonia-borane dehydrogenation catalysis [5].
Assessment of these cationic and neutral Fe(II) complexes as catalysts for ammonia-borane
dehydrogenation will be presented and discussed.
Scheme 1: Preparation of Fe(II) SNS Complexes
Scheme 2: Selective Hydroboration of Aldehydes and Ammonia Borane
Dehydrogenation
References
[1] K. Junge, K. Schroder, M. Beller, Chem. Commun. 2011, 47, 4849.
[2] I. Bauer, H.-J. Knölker, Chem. Rev. 2015, 115, 3170.
[3] U. K. Das, S. L. Daifuku, S. I. Gorelsky, I. Korobkov, M. L. Neidig, J. J. Le Roy, M. Murugesu, R.
T. Baker, Inorg. Chem. 2016, 55, 987.
[4] C. C. Chong, R. Kinjo, ACS Catal. 2015, 5, 3238.
[5] R. T. Baker, J. C. Gordon, C. W. Hamilton, N. J. Henson, P.-H. Lin, S. Maguire, M. Murugesu, B.
L. Scott, N. C. Smythe, J. Am. Chem. Soc. 2012, 134, 5598.
89
PP16 - Neutral Captodative Biradicals Stabilized by Cyclic
(Alkyl)(Amino)Carbenes
Holger Braunschweig,* Andrea Deißenberger, Regina Drescher, Kai Hammond, Ivo
Krummenacher
Department of Inorganic Chemistry
Julius-Maximilians Universitaet Wuerzburg
97074 Wuerzburg, Germany
Anionic boryl radicals have been investigated for decades,[1] whereas the field of the
isoelectronic neutral compounds remained rather scarcely investigated. However, neutral
boryl radicals have emerged in recent years and a few examples of Lewis-base-stabilized
boryl radicals could be isolated and characterized.[2] N-heterocyclic carbenes (NHC) have
been employed to stabilize the lone electron at boron by Curran and coworkers. [3] These
neutral boryl radicals were recently applied to various organic radical reactions, such as
radical deoxygenation of xanthates, radical reductions of alkyl halides and radical chain
homolytic substitution reactions.
Based on these results, the first neutral boron-containing radicals stabilized by cyclic
(alkyl)(amino)carbenes (CAAC) were synthesized and fully characterized by our group.[4]
These radicals showed an extraordinary stability to high temperatures as well as a larger
spin density on boron, compared to known boryl radicals. In this work, we show the first
synthesis
of
a
neutral
boron-containing
biradical
stabilized
by
cyclic
(alkyl)(amino)carbenes. The synthesis starts with the addition of B2Cl4 to an alkyne,
followed by the stabilization of this diborylated species with one equivalent of the CAAC
forming the intramolecular stabilized compound 1. Reduction using potassium graphite in
the presence of another equivalent of CAAC leads to the deep blue colored biradical 2.
Structural characterization by X-ray analysis shows comparable bonding parameters to the
previously published CAAC-stabilized radicals of our group. EPR studies show a large
hyperfine coupling of each unpaired electron with both the nitrogen and the boron atom,
indicating isolated radical sites.
Bibliography
[1] e.g. H. Braunschweig, V. Dyakonov, J.O.C. Jimenez-Halla, K. Kraft, I. Krummenacher, K.
Radacki, A. Sperlich, J. Wahler, Angew. Chem. Int. Ed. 2012, 51, 2977.
[2] e.g. C.-W. Chiu, F.P. Gabbaï, Angew. Chem. Int. Ed. 2007, 46, 1723.
[3] e.g. S.-H. Ueng, A. Solovyev, X. Yuan, S.J. Geib, L. Fensterbank, E. Lacôte, M. Malacria,
M. Newcomb, J. C. Walton, D.P. Curran, J. Am. Chem. Soc. 2009, 131, 11256.
[4] P. Bissinger, H. Braunschweig, A. Damme, I. Krummenacher, A.K. Phukan, K. Radacki, S.
Sugawara, Angew. Chem. Int. Ed. 2014, 53, 7360.
90
PP17 - Formation of Boron-Boron Multiple BondsA Creeping
Crossover from Diborynes to Diboracumulenes
Julian Böhnke, Holger Braunschweig,* Theresa Dellermann, Kai
Hammond, Jan Mies
Since the successful synthesis of the first ambient-temperature-stable diboryne, a series of
new compounds with boron-boron multiple bonds have been synthesized using a range of
different donating ligands.[1] Changing the NHC unit to a cyclic (amino)(alkyl)carbene
(CAAC) leads to the formation of a diboracumulene-type compound.[2] Our main goal was
to synthesize a diboryne that is more reactive than the original B2IDip2 through the use of
slightly different ligands with saturated backbones or smaller groups at the nitrogen atoms.
The result is a stepwise lengthening of the boron-boron bond along with a shortening of
the boron-carbon bond.[3] The different electronic structures of these complexes were
confirmed through reactivity studies. Whereas the original diboryne B2IDip2 complexes
cations through electrostatic interactions to the triple bond, the same reactivity could not
be observed for B2CAAC2.[4] In contrast, a 1,2-addition of molecular hydrogen could only
be obtained for the diboracumulene molecule. Their reactivity towards CO clearly
illustrates the difference between the pure-diboryne and pure-diboracumulene examples.
B2SIDip2 and B2SIDep2 react with CO to form bis(CO) adducts (B2L2(CO)2), which in the
case of B2CAAC2 is the final product, but also go on to form a bis(boralactone) species, as
was observed with B2IDip2, indicating their position on the diboryne/diborene continuum
somewhere between B2IDip2 and B2CAAC2.[3,5]
Bibliography
[1] H. Braunschweig, R. D. Dewhurst, K. Hammond, J. Mies, K. Radacki, A. Vargas, Science 2012, 336, 1420. J.
Böhnke, H. Braunschweig, P. Constandinidis, T. Dellermann, W. C. Ewing, I. Fischer, K. Hammond, F. Hupp, J.
Mies, H. C. Schmitt, A. Vargas, J. Am. Chem. Soc. 2015, 137, 1766.
[2] J. Böhnke, H. Braunschweig, W. C. Ewing, C. Hörl, T. Kramer, I. Krummenacher, J. Mies, A. Vargas, Angew.
Chem. Int. Ed. 2014, 53, 9082.
[3] J. Böhnke, H. Braunschweig, T. Dellermann, W. C. Ewing, K. Hammond, T. Kramer, J. O. C. Jimenez-Halla, J.
Mies, Angew. Chem. Int. Ed. 2015, 54, 13801.
[4] R. Bertermann, H. Braunschweig, P. Constantinidis, T. Dellermann, R. D. Dewhurst, W. C. Ewing, I. Fischer, T.
Kramer, J. Mies, A. K. Phukan, A. Vargas, Angew. Chem. Int. Ed. 2015, 54, 13090.
[5] H. Braunschweig, T. Dellermann, R. D. Dewhurst, W. C. Ewing, K. Hammond, J. O. C. Jimenez-Halla, T.
Kramer, I. Krummenacher, J. Mies, A. K. Phukan, A. Vargas, Nat. Chem. 2013, 5, 1025.
91
PP18 - Boron Nanoparticles linked to 5-Thio-D-Glucopyranose: A Novel
Cancer Therapy Agent
Rebecca Dominguez, Narayan S. Hosmane*
Northern Illinois University
Dekalb, IL, 60115, United States
Boron nanoparticles linked to 5-Thio-D-Glucopyranose are potential drug carriers for use
in Boron Neutron Capture Therapy (BNCT). BNCT is a bimodal cancer therapy that is
being developed as an alternative to current cancer treatments such as radiation therapy
and chemotherapy. Unlike many current therapies, BNCT is a targeting cancer therapy
that does not harm the healthy tissues surrounding the tumor. The carrier drug in this
project consists of boron nanoparticles that are attached to 5-Thio-D-glucopyranose
molecules via polyethylene glycol links. The product was characterized by standard
techniques used for nanomaterials, including Nuclear Magnetic Resonance (NMR)
spectroscopy, Transmission Electron Microscopy (TEM), Fourier-Transform Infrared
spectroscopy (FTIR), and Energy-Dispersive X-ray spectroscopy (EDX).
92
PP19 - PNPCB Heterocycles via Thermal and Lewis Acid Catalyzed
trans-Hydroborations
Louie Fan, Doug W. Stephan*
While a seemingly endless number of cyclic organic derivatives have been prepared and
characterized, novel synthetic routes to heterocycles containing inorganic elements have also
drawn attention. The interest in B-containing heterocycles has inspired us to prepare related
boron-based heterocyclic systems, however we targeted systems that also contain additional
heteroatoms. We have previously studied the reaction of “click reactions” of boron-azides with
phosphaalkynes 1, 2, and alkynl boranes3 which afford routes to unprecedented boron
heterocycles and macrocycles. Herein, we discuss PNPCB heterocycles formed from
subsequent reactions between phosphaalkynes and phosphazides. The compounds
iPr2P(BH3)N3 and R2PCCR’ (R = tBu, Ph, R’ = Ph, Cy, tBu) were reacted to give the
staudinger type products R2P(C≡CR’)NP(BH3)iPr2. Subsequently, intramolecular
hydroboration can be induced either thermally or catalytically to afford heterocyclic PNPCB
compounds with a unique net trans-hydrboration. Staudinger compounds and heterocyclics
were crystallographically characterized and the mechanisms for both thermal and catalytic
hydroboration are proposed.
Bibliography
[1] R. L. Melen and D. W. Stephan, Dalton Trans., 2013, 42, 4795-4798. 10.
[2] R. L. Melen, A. J. Lough and D. W. Stephan, Dalton Trans., 2013, 42, 8674-8683.
[3] D. Winkelhaus and D. W. Stephan, Angew. Chem. Int . Ed., 2014, 53, 5414-5417.
93
PP20 - Water tolerant B(C6F5)3 Catalyzed Reductive Amination Using
Hydrosilanes
Valerio Fasano, James E. Radcliffe and Michael J. Ingleson*
School of Chemistry
Manchester, M13 9PL, United Kingdom
The past decade has witnessed spectacular advances in metal-free catalytic reductions,
particularly using “frustrated Lewis pairs”.1 Numerous advances built on the pioneering
work of Piers (using hydrosilanes)2 and Stephan (using H2)3 have led to B(C6F5)3, being
established as a versatile reduction catalyst. In contrast to the general perception that
B(C6F5)3 is irreversibly poisoned by excess H2O / amine (or imine) bases, B(C6F5)3 is
actually a water tolerant catalyst for the reductive amination of primary and secondary
arylamines with aldehydes and ketones in “wet solvents” at raised temperatures and using
only 1.2 equivalents of PhMe2SiH as reductant, insufficient to both dry the reaction mixture
(by dehydrosilylation of H2O) and reduce the imine.4 Arylamines / N-arylimines do not
result in the irreversible deprotonation of H2O-B(C6F5)3 allowing sufficient B(C6F5)3 to be
evolved at raised temperatures to effect catalytic reductions. A substrate scope exploration
using 1 mol% non-purified B(C6F5)3 and “wet solvents” demonstrate that this is an
operationally simple methodology for the production of 2o and 3o arylamines in high yield,
with imine reduction proceeding in preference to other reactions catalyzed by B(C6F5)3,
including the reduction of carbonyl moieties2 and the C-F activation of fluorinated
substrates.5
Scheme. B(C6F5)3 catalyzed reductive amination using hydrosilane
Bibliography:
1
Stephan, D. W., J. Am. Chem. Soc., 2015, 137, 10018-10032.
2
Piers, W. E. et al., J. Am. Chem. Soc., 1996, 118, 9440-9441.
3
Stephan, D. W. et. al., Science, 2006, 314, 1124-1126.
4
Ingleson, M. J. et. al., ACS Catal., 2016, 6, 1793-1798.
5
Stephan, D. W. et al., Organometallics, 2012, 31, 27-30.
94
PP21 - Brønsted Acid-Catalyzed Reactions of Potassium
Trifluoroborate Salts with In Situ Generated Carbocations
Kayla M. Fisher, Yuri Bolshan*
Faculty of Science
University of Ontario Institute of Technology
Oshawa, ON, L1H 7K4, Canada
Metal-free transformations of organotrifluoroborates are advantageous since they avoid
the use of frequently expensive and sensitive transition metals. Recently, Lewis acidcatalyzed reactions involving potassium trifluoroborate salts have emerged as an
alternative to metal-catalyzed protocols.[1] However, the drawbacks to these methods are
that they rely on the generation of unstable boron dihalide species thereby resulting in low
functional group tolerance. Recently, we discovered that in the presence of a Brønsted
acid, trifluoroborate salts react rapidly with in situ generated stabilized carbocations. A
reaction of potassium trifluoroborate salts with benzhydryl alcohols proceeded when
tetrafluoroboric acid was used as a catalyst.[2] Subsequently, we have established that
acetals and ketals act as suitable starting materials under similar reaction conditions.[3]
Benzhydryl alcohols react with trifluoroborate salts in 1:1 ratio to yield the desired
products. Excellent functional group tolerance allowed for the presence of unprotected
amide, aldehyde, free hydroxyl, and carboxylic acid functional groups. Furthermore,
2-ethoxytetrahydrofuran undergoes direct functionalization under the developed conditions
to afford the desired products in good to excellent yields.[4] A variety of alkenyl- and
alkynyltrifluoroborate salts readily participate in both transformations.
Bibliography
[1] Roscales, S.; Csákÿ, A. G. Chem. Soc. Rev. 2014, 43, 8215-8225.
[2] Fisher, K. M.; Bolshan, Y. J. Org. Chem. 2015, 80, 12676-12685.
[3] Baxter, M.; Bolshan, Y. Chem. Eur. J. 2015, 21, 13535-13538.
[4] Fisher, K. M.; Bolshan, Y. unpublished results
95
PP22 - C–H Activation/Borylation of Amide Directed Aromatics using
Ruthinium Catalyst
Jia Yang, Yigang Zhao, Sahaj Gupta, Victor Snieckus*
The discovery of the Suzuki-Miyaura reaction1 more than three decades ago led to the
resurgence of organoboron chemistry and this reaction has found utility not only in organic
synthesis, but has vast impact in areas of material sciences, medicinal chemistry and drug
discovery.2 In contrast to classical strategies that used for synthesis of aromatic boronic
acid from aryl hallides,3 the directed ortho metalation (DoM) and transition metal-catalyzed
direct borylation approaches provide regioselective and abbreviated access to the
synthetically useful ortho-borylated aromatics. This presentation will be concerned with
new methodology for the synthesis of organoboron compounds via Ru-catalyzed ortho
selective C-H borylation of tertiary benzamides, which complements the earlier work
reported by our group that involved an Ir-catalyzed meta borylation protocol.4 This orthoborylation reaction has advantages in comparison to the DoM protocol4 in that no
cryogenic conditions are required. It allows access to 1,2- and 1,2,4-substituted benzenes
and the attainment of one-pot C-H borylation/cross-coupling procedures.
Bibliography
[1] N. Miyaura, K. Yamada, A. Suzuki, Tetrahedron Lett. 1979, 20, 3437; b) N. Miyaura, A.
Suzuki, J. Chem. Soc., Chem. Commun. 1979, 866.
[2] A. O. King, N. Yasuda, Topics Organomet Chem 2004, 6, 205.
[3] I. A. I. Mkhalid, J. H. Barnard, T. B. Marder, J. M. Murphy, J. F. Hartwig, Chem. Rev. 2009,
110, 890.
[4] T. E. Hurst, T. K. Macklin, M. Becker, E. Hartmann, W. Kügel, J. C. Parisienne-LaSalle, A.
S. Batsanov, T. B. Marder, V. Snieckus, Chem. - A Eur. J. 2010, 16, 8155.
96
PP23 - The mixed alloyed chemical composition of chloro–(chloro)nboron subnaphthalocyanines dictates their physical properties and
performance in organic photovoltaic devices1
Jeremy D. Dang, Devon P. Holst, Timothy P. Bender*
Chloro-boron subnaphthalocyanine (Cl-BsubNc) has recently attracted significant interest
as a light-harvesting and charge transporting material in organic photovoltaic devices
(OPVs) by enabling an 8.4% efficient planar heterojunction OPV cell.2 Presented is a
variety of experimental data supporting the conclusion that Cl-BsubNc, whether
synthesized via literature methods3,4, our in-house methods, or purchased commercially, is
actually a mixed alloyed composition of Cl-BsubNcs with random amounts of chlorination
at the bay position(s) of the BsubNc macrocyclic structure. The positions and frequencies
of the peripheral chlorine atoms were determined via single crystal X-ray crystallography of
two different mixed alloyed composition Cl–BsubNc samples and MS and XPS analysis of
all Cl–BsubNc samples. The photo- and electro-physical properties were found to differ
amongst the Cl–BsubNc samples with varying amounts of chlorination. These differences
also translated into varying performance within planar heterojunction OPVs, whereby a
mixture of Cl–BsubNcs with lower amounts of chlorination produced less efficient OPVs
compared to a mixture with higher amounts of chlorination. Additionally, an in-house made
sample of Cl–BsubNc, with the highest level of bay position chlorination, yielded the best
performing OPVs through an improved fill factor. A commercial sample of Cl–BsubNc also
yielded OPVs with efficiencies equivalent to a Cl–BsubNc sample prepared in our
laboratory. This mixture of Cl–BsubNcs is therefore likely to be present in the reported 8.4%
efficient OPV device.2 These results offer
a cautionary note that the Cl-BsubNc
samples used within existing literature are
likely not a pure chemical composition, but
rather a mixture of Cl–BsubNcs with bay
position chlorination. These findings clarify
the previous literature results on the
chemistry of Cl-BsubNcs, firm up the
photo- and electro-physical properties of
these materials, and offer additional
insight into their application as functional materials in efficient OPVs.
Bibliography
[1] J. D. Dang, D. Josey, A. Lough, Y. Li, A. Sifate, Z. Lu and T. P. Bender, J. Mater.
Chem. A, 2016, DOI: 10.1039/C6TA02457B.
[2] K. Cnops, M. A. Empl, P. Heremans, B. P. Rand, D. Cheyns and B. Verreet, Nat.
Commun., 2014, 5, 3406.
[3] S. Nonell, N. Rubio, B. del Rey and T. Torres, Perkin 2, 2000, 1091–1094.
[4] C. D. Zyskowski and V. O. Kennedy, J. Porphyrins Phthalocyanines, 2000, 4, 707–712.
97
PP24 - Insertion of CO2 into the C-B Bond of a Borylated 4,5Diazafluorenyl Ru(II) Complex
Trevor Janes, Kimberly M. Osten, Yanxin Yang, and Datong Song*
80 St. George St. Toronto, ON, Canada M5S 3H6
The accumulation of carbon dioxide in the atmosphere has led synthetic chemists to
develop transformations which incorporate CO2 into more valuable products. [1] Discovery
of new fundamental modes of reactivity for the CO2 molecule has been a focus of our
research group: we demonstrated formal insertion of CO2 into a C-H bond of an actor
diazafluorenide ligand bound to a variety of spectator metal centres. [2] We elaborated this
reactivity to include metal-free insertions and catalytic hydroboration of CO2. [3] To extend
this work, we generated a ruthenium-bound borylated diazafluorenide ligand via template
synthesis (crystal structure shown below), and we investigated the behaviour of this actor
ligand towards CO2. [4] This poster presentation will detail what is, to the best of our
knowledge, the first example of insertion of CO2 into a C-B bond, and application of this
reactivity in the catalytic hydroboration of CO2.
References
[1] Liu, Q.; Wu, L.; Jackstell, R.; Beller, M. Nat. Commun. 2015, 6, 5933.
[2] Annibale, V. T.; Dalessandro, D. A.; Song, D. J. Am. Chem. Soc. 2013, 135, 16175
[3] Yang, Y.; Xu, M.; Song, D. Chem. Commun. 2015, 51, 11293
[4] Janes,T.; Osten, K. M.; Pantaleo, A.; Yan, E.; Yang, Y.; Song, D. Chem. Commun. 2016,
52, 414
98
PP25 - Synthesis of Fluorescein-Tagged and Water-Soluble CarboraneAppended Compounds
L. Kuzmanic, G. Poci, L. Zuidema, V. Kalavakunda, N. Hosmane*
DeKalb, IL 60115
Boron neutron capture therapy (BNCT) is a method of cancer treatment that involves
killing cancer cells through a nuclear reaction of two nontoxic species, boron-10 (10B) and
thermal neutrons. The helium α-particles and lithium nuclei that result produce closely
spaced ionizations near the reaction site and dissipate their kinetic energy over the
diameter of the cell. The lethality of these particles is limited to only boron-containing cells,
and therefore, the most important requirement of BNCT is the amount and selective
accumulation of 10B into the cancer cells while minimizing uptake into the surrounding
healthy tissue. Current research in BNCT focuses on the synthesis of novel compounds
with high boron content as well as methods for their delivery into the tumor cell. For BNCT
applications, the water-solubility of such boron containing compounds must be resolved
through chemical modification. Water-solubility is highly desirable for biological evaluation
and can be accomplished through decapitation of the carborane cage moiety. Additionally,
a fluorescent tag can allow the observation of their cellular uptake during biodistribution
studies. Accordingly, several selected biomolecules and fluorescein were conjugated with
iodinated o-carborane and characterized using Fourier-transform infrared spectroscopy
(FTIR), nuclear magnetic resonance spectroscopy (NMR), elemental analysis, and mass
spectrometry (MS).
99
PP26 - Synthetic Efforts Toward Diamidocarbene- Supported Terminal
Borylenes
Anthony D. Ledet, Todd W. Hudnall*
Department of Chemistry & Biochemistry
Texas State University
San Marcos, Tx 78666
Stable carbenes have recently emerged as the preeminent ligands for the stabilization of
reactive species. As a part of our efforts to this field, we have been actively exploring the
ability of carbonyl-decorated carbenes such as diamidocarbenes (DACs), which behave as
moderate π-accepting ligands, to stabilize low-oxidation state main group species. To
further develop this paradigm, a recent focus has been on the design and synthesis of
terminal borylenes that are supported by DACs. This presentation will focus on our
struggles and developments toward the isolation of these elusive species. Specifically, we
will discuss the reactions of DACs with the dichloroboranes, dichlorophenylborane,
dichloro(diisopropylamino)borane, and dichloro-(1,2,3,4,5-pentamethylcyclopenta-2,4dienyl)borane, and the subsequent reduction reaction of the reaction products to afford
boron(II)-centered radicals.
First approach – direct reduction: This work is motivated by Cowley’s discovery of
the first stable borylene metal complex which contained an h5-Cp* borylene: See
Cowley, JACS, 1998, 6401
Second approach – halide abstraction followed by reduction: See Ching-Wen Chiu,
ACIE 2013, 52, 13293
100
PP27 - Metal-free Csp2-H bond activation and borylation by frustrated
Lewis pairs toward convenient catalysis
Julien Légaré Lavergne, Nicolas Bouchard, Étienne Rochette, Marc-André Légaré,
Frédéric-Georges Fontaine*
Université Laval
Frustrated Lewis pairs (FLPs) are well known for their ability to activate small molecules such
as hydrogen.1 This discovery led to several advances in the catalytic metal-free
hydrogenation of unsaturated compounds.2 Recently, our research group reported the
catalytic borylation of heteroarenes using a FLP as a catalyst. This reaction proceeds via an
activation of a Csp2-H bond of the substrate by an ambiphilic molecule containing a bulky
amine and a BH2 moiety.3 Later on, we reported that this catalysis can also be achieved by
fluoroborate derivatives of the previous molecule. The BH2 moiety is generated in situ by the
borylating agent pinacolborane. This gives acces to bench-stable precatalysts for the
borylation reaction without the need of a glovebox apparatus.4
This presentation will detail our work in attempting to increase the activity of FLPs as
catalysts for the borylation reaction.
Bibliography
[2] Stephan, D. W.; Erker, G. FLP chemistry: Topics in Current Chemistry; Eds.; Springer:
New York, 2013; Vols, 332, and 334.
513-516.
[4] Légaré, M.-A.; Rochette, É.; Lavergne, J. L.; Bouchard, N.; Fontaine, F.-G. Chem.
Commun. 2016, 52, 5387-5390.
101
PP28 - The Synthesis and Reactivity of Stable Borocyclic Radicals
Lauren E. Longobardi and Douglas W. Stephan*
Frustrated Lewis pair (FLP) chemistry harnesses the unquenched reactivity of stericallyencumbered combinations of Lewis acids and bases to activate small molecules.1,2This
discovery has led to the development of main group systems for catalytic reductions and
other important transformations.3–6 Despite high demand, the synthesis of highly
electrophilic borane species, which are fundamental to FLP chemistry, is an ongoing
challenge. We recently reported the stoichiometric reduction of alkyl-substituted ketones
using B(C6F5)3 and H2 to generate new borinic ester products.7 We have further explored
this methodology to achieve the synthesis of stable, borocyclic radicals, which display
unique behaviour in FLP chemistry.8 The synthesis of these radicals along with their
physical properties and reactivity will be presented.
F
F
F
F
F
F
F
F
O
O
F
F
F
FF
F
F
B
O
O
F
FF
F
F
B
O
O
PR 3
C6F 5
B
O
O
PR 2
References:
(1)
Welch, G. C.; San Juan, R. R.; Masuda, J. D.; Stephan, D. W. Science 2006, 314,
1124.
(2)
McCahill, J. S. J.; Welch, G. C.; Stephan, D. W. Angew. Chem. Int. Ed. 2007, 46,
4968.
(3)
Stephan, D. W.; Erker, G. Angew. Chem. Int. Ed. 2015, 54, 6400.
(4)
Stephan, D. W. J. Am. Chem. Soc. 2015, 137, 10018.
(5)
Stephan, D. W. Acc. Chem. Res. 2015, 48, 306.
(6)
Bayne, J. M.; Stephan, D. W. Chem. Soc. Rev. 2015, 45, 765.
(7)
Longobardi, L. E.; Tang, C.; Stephan, D. W. Dalton Trans. 2014, 43, 15723.
(8) Longobardi, L. E.; Liu, L.; Grimme, S.; Stephan, D. W. J. Am. Chem. Soc. 2016, 138,
2500.
102
PP29 - Examination of Aggregation-Induced Emission in Boron
Difluoride Complexes of 3-Cyanoformazanates
Ryan R. Maar and Joe B. Gilroy*
Department of Chemistry and the Centre for Advanced Materials
and Biomaterials Research (CAMBR)
E-mails: [email protected], [email protected]
Molecules that exhibit aggregation-induced emission (AIE) or aggregation-induced emission
enhancement (AIEE) have garnered significant attention due to their applicability to the fields
of organic electronics, chemical sensing, and fluorescence cell imaging.1−3 Typically, organic
fluorophores experience attenuated emission intensity upon aggregation as a result of
aggregation-caused quenching (ACQ).4 This arises due to the formation of strong
intermolecular π-π stacking interactions enabling the formation of excimers/exciplexes, which
quench excited states via non-radiative pathways. Previous work in the Gilroy group has
focused on the synthesis of boron difluoride (BF2) complexes of 3-cyanoformazanates. These
compounds possess tunable absorption, emission, and electrochemical properties through
structural variation5 and are viable candidates for fluorescence cell imaging.6 This poster
presentation will describe the first examples of BF2 formazanates that demonstrate AIE. In
addition, the synthetic strategy, X-ray crystallographic data, and the electrochemical and
spectroscopic properties of the resulting complexes 1−3 will be discussed.
MeO
F F
B
N
N
N
N
CN
1
fw
OMe
MeO
F F MeO
B
N
N
N
N
CN
2
fw
F F MeO
B
N
N
OMe
N
N
OMe
MeO
CN
3
fw
References
[1] J. Mei, Y. Hong, J. W. Y. Lam, A. Qin, Y. Tang and B. Z. Tang, Adv. Mater., 2014, 26,
5429.
[2] J. Mei, N. L. C. Leung, R. T. K. Kwok, J. W. Y. Lam and B. Z. Tang, Chem. Rev., 2015,
115, 11718.
[3] H. Wang, E. Zhao, J. W. Y. Lam and B. Z. Tang, Mater. Today, 2015, 18, 365.
[4] J. B. Birks, Photophysics of Aromatic Molecules, Wiley, New York, 1970.
[5] S. M. Barbon, P. A. Reinkeluers, J. T. Price, V. N. Staroverov and J. B. Gilroy, Chem.
Eur. J., 2014, 20, 11340.
[6] R. R. Maar, S. M. Barbon, N. Sharma, H. Groom, L. G. Luyt and J. B. Gilroy, Chem.
Eur. J., 2015, 21, 15589.
103
PP30 - Cucurbit[7]uril Host-Guest Complexes of Amine Boranes in
Aqueous Solution
Donal H. Macartney* and Mona Gamal-Eldin
Amine boranes have utility in reductions of aldehydes and ketones, and in hydrogen
storage through dehydrogenation reactions [1]. Aside from some investigations on the
complexation of ammonia borane by crown ethers [2], there has been little study of the
supramolecular host-guest complexation of amine boranes and the effects on their
reactivity in solution. We have shown that the macrocyclic cucurbit[7]uril host molecule [3,4]
is selective towards hydrophobic quaternary ammonium cations of different sizes [5]. We
have recently investigated the host-guest complexation of a series of N-alkyl (methyl, ethyl,
t-butyl, and morpholine) derivatives of ammonia borane by CB[7] in aqueous solution using
multinuclear NMR spectroscopy [6]. The complexation-induced chemical shift changes
support the inclusion of the guests within the hydrophobic cavity of the host and the hostguest stability constants have been determined by competitive NMR binding experiments,
and compared with the corresponding quaternary ammonium cations.
H
H
N
B
-0.39
H
-0.78 H
CH3
-0.83
CH3
CH3
CH3
H
N
-0.79
B -0.78 CH3
H
-0.71
H
H2C
CH3
CH3
CH2
-0.56
C CH3
H
-0.78 H2
-0.78
-0.86
H
H
N
B
CB[7] Complexation-Induced Chemical Shift Changes (ppm)
H
H
H
CH3
-0.78
C CH3
N
B -0.91 H CH3
H
H -0.75
H
-0.46 -0.88
O
BH
H
H
N
-0.72 H
-0.60
H
-0.89
H
-0.95
H
H -0.91
H
B N
H
-0.70 H
CH3
-0.78
O
H -0.61
H
-0.80
{CB[7]●H3Bmorpholine}
Bibliography
[1] Staubitz, A.; Robertson, A. P. M.; Manners, I. Chem. Rev. 2010, 110, 4079.
[2] Colquhoun, H. M.; Jones, G.; Maud, J. M.; Stoddart, J. F.; Williams, D. J. J. Chem. Soc.,
Dalton Trans., 1984, 63
[3] Barrow, S. J.; Kasera, S.; Rowland, M. J.; del Barrio, J.; Scherman, O. A. Chem. Rev.
2015, 115, 12320.
[4] Macartney, D. H. Isr. J. Chem., 2011, 51, 600.
[5] St-Jacques, A. D.; Wyman, I. W.; Macartney, D. H. Chem. Commun., 2008, 4936.
[6] Gamal-Eldin, M. A.; Macartney, D. H., manuscript in preparation.
104
PP31 - Aqueous Interactions With Silicone Boronate Esters: Formation
and Mechanical Properties of Silicone Boronic Acid Elastomers
Benjamin Macphail, Laura Zepeda-Velazquez, Michael A. Brook*
Chemistry and Chemical Biology
McMaster University, Hamilton, ON, Canada
Highly labile boronic esters can be hydrolysed on contact with aqueous surfaces to
produce the corresponding boronic acids[1], which in turn can form complexes with a
variety of ligands, including other boronic acids [2]. Silicone elastomers are normally
crosslinked through covalent linkages. This work examines the use of boronic acid
complexation as a new way to make silicone elastomers. Both pendant-arranged and
telechelic-arranged tartrate ester-protected silicone-boronic acid polymers with different
molecular weights and boronic acid densities were synthesized via hydrosilylation [3].
These polymers were exposed to moisture, which led to hydrolysis of tartrate protecting
groups and an immediate and dramatic change in physical properties (Scheme 1).
Scheme 1. Telechelic silicone boronate ester synthesis and polymerization by boronic
acid complexation via hydrolysis.
Low viscosity oils were transformed into viscoelastic films even in the absence of
coordinating Lewis bases: Lewis acid/Lewis base complexation provides a different route
to crosslinking. Although the protected oil spreads readily, upon water exposure, very rapid
boronic ester hydrolysis occurred at a water-silicone interface and the free boronic acids
adhered both to water and other boronic acids: 1:1 complexes form, which facilitates
crosslinking. The stability of these films was tested to better understand the impact of
molecular weight and density of boronic acid appendages on mechanical properties. We
will discuss the surprisingly high level of control over mechanical properties that is possible
simply by changing these two parameters.
References:
1.
Achilli, C., et al., Susceptibility to hydrolysis of phenylboronic pinacol esters at physiological
pH. Cent. Eur. J.Chem., 2013. 11(2): p. 137-139.
2.
Mansuri, E., et al., Surface Behavior of Boronic Acid-Terminated Silicones. Langmuir, 2015.
31(34): p. 9331-9339.
3.
Dodge, L., Y. Chen, and M.A. Brook, Silicone Boronates Reversibly Crosslink Using Lewis
Acid–Lewis Base Amine Complexes. Chem. Eur. J., 2014. 20(30): p. 9349-9356.
105
PP32 - Applications of Boronic Acids for Regioselective
Functionalization of Unprotected Pyranose Substrates
Ross Mancini, Jessica Lee, Mark S. Taylor*
Toronto, ON, M5S 3H6
Interactions between carbohydrates and boron-based compounds have a rich history,
leading to applications in carbohydrate detection, biological imaging and drug delivery. [1] In
carbohydrate synthesis, selective binding of boronic acids to cis-1,2- and 1,3-diols can be
exploited to perform regioselective functionalizations on minimally protected glycosyl
acceptors via transient protection of the boron-bound hydroxyl groups.[2] Despite the
potential advantages this strategy may provide (mild installation/cleavage of boronic esters,
orthogonality to acetal protection methods), few examples of this approach are reported in
the literature. Given the need for methods that enable rapid production of differentially
protected carbohydrates, our lab has decided to re-investigate the potential of boronic
acids for the production of differentially protected carbohydrate building blocks. Herein we
describe a method that uses commercially available arylboronic acids to regioselectively
install a variety of functional groups (acyl, alkyl, silyl, carbonate) to unprotected methyl
glycosides. The boronic esters can be hydrolysed upon basic work-up[3] to yield selectively
functionalized monosaccharides, or activated with Lewis base[4] to perform a sequential
regioselective glycosylation at a boron-bound oxygen. Both methods require only a single
chromatographic purification step, allowing rapid throughput to highly functionalized
products from unprotected starting materials.
References:
[1] McClary, C.A.; Taylor, M.S. Carbohydr. Res. 2013, 381, 112–122.
[2] (a) Ferrier, R. J. Adv. Carbohydr. Chem. Biochem. 1978, 35, 31–80; (b)
Duggan, P. J.; Tyndall, E. M. J. Chem. Soc., Perkin Trans. 1, 2002, 1325–1339.
[3] Mothana, S.; Grassot, J.-M.; Hall, D.G. Angew. Chem. Int. Ed. 2010, 49, 2883–
2887.
[4] (a) Mancini, R.S.; McClary, C.A.; Anthonipillai, S.; Taylor, M.S; J. Org. Chem.
2015, 80, 8501–8510. (b) Oshima, K.; Aoyama, Y. J. Am. Chem. Soc. 1999, 121,
2315–2316.
106
PP33 - Boronic Acid-Promoted Fischer Glycosidations
Sanjay Manhas and Mark S. Taylor*
Reversible covalent interactions between boronic acids and diols have been exploited
extensively in the chemical sensing and recognition of saccharides [1] and as tools for
facile assembly of complex molecular scaffolds [2]. We have found that boronic acids can
be employed as recoverable [3] phase transfer reagents, transiently protecting
monosaccharides and facilitating Fischer glycosidations in non-polar solvents. This allows
access to a wide array of acceptors with varying monosaccharide configurations.
Experimental and computational data suggest that the binding of boronic acids to free
monosaccharides can alter the thermodynamics of the reaction, allowing isolable products
not attainable under current Fischer glycosidation conditions [4,5].
Bibliography
[1] Shinkai, S. J. Am. Chem. Soc. 1995, 117, 8982–8987
[2] Kataoka, K.; James T.D.; Kubo, Y. J. Am. Chem. Soc. 2007, 129, 15126–15127
[3] Mothana, S.; Grassot, JM.; Hall, D.G. Angew. Chem. Int. Ed. 2010, 49, 2883–2887
[4] Roy, K.D.; Bordoloi, M. Journal of Carbohydrate Chemistry 2008, 27:5, 300–307
[5] Bornaghi, F.L.; Poulsen, S. Tetrahedron Letters 2005, 46, 3485–3488
107
PP34 - Alkyne Trans-hydroboration Using Boron Lewis Acid Catalysis.
John S. McGough, Samuel M. Butler, Ian A. Cade, Michael J. Ingleson*
Deparment of Chemsitry
Univeristy of Manchester
Oxford Road, Manchester, United Kingdom M13 9PL
Three coordinate boro-cations (borenium cations) have attracted significant interest over
recent years as highly reactive and versatile reagents and catalysts.1,2 Herein, we present
the use of N-heterocyclic carbene (NHC) stabilised boreniums in the intermolecular transhydroboration of terminal alkynes to give Z-alkenes; and internal alkynes to give E-alkenes,
in a direct compliment to conventional cis-hydroboration.3 The trans-hydroboration of
alkynes (which is rare even with transition metal catalysts)4a-f proceeds rapidily using
catalytic B(C6F5)3 with 9-BBN(H)(NHC) species, affording the alkene products in good to
excellent yields with high regio- and stereo- control.5 In addition, the strongly Lewis-acidic
neutral borane B(C6F5)3 also initiaites alkyne trans-hydroboration in the presence of a
hydride donor.
References:
Ingleson, M.J., Fundamental and Applied Properties of Borocations, Topics In
Organometallic Chemistry: Synthesis and Application of Organoboron Compounds,
Fernandez, E., Whiting, A., Ed., Springer: Switzerland, 2015, Vol 49., p39-71. DOI:
10.1007/978-3-319-13054-5, ISBN: 978-3-319-13053-8
2 De Vries, T.S., Prokofjevs, A., Vedejs, E., Chem Rev., 2012, 112, 4246.
3 Brown, H. C., Ravindran, N. Inorg. Chem. 1977, 16, 2938.
4 a) Ohmura T., Yamamoto Y., Miyaura N., JACS. 2000, 122, 4990, (b) Gunanathan C.,
Holscher M., Pan, F., Leitner W., JACS. 2012, 134, 14349 (c) Sundararaju B., Fürstner A.,
ACIE, 2013, 52, 14050, (d) Xu S., Haeffner F., Li B., Zakharov L.V., Liu S.-Y., ACIE, 2014,
53, 6795 (e) J. V. Obligacion, J. M. Neely, A. N. Yazdani, I. Pappas, P. J. Chirik, JACS.,
2015, 137, 5855. (f) Yuan, K., Suzuki, N., Mellerup, S.K., Wang, X., Yamaguchi, S., Wang,
S., Org. Lett., 2016, 16, 720.
5
McGough, J.S, Butler, S.M., Cade, I.A., Ingleson, M.J., Chem. Sci., 2016,
10.1039/C5SC04798F.
108
PP35 - Synthesis of new borole compounds based on thiophene
derivatives
Holger Braunschweig* and Michael Meier
Boroles are intensely colored, five-membered heterocyclic systems with four π-electrons
delocalized through an empty boron pz orbital.[1,2] Isoelectronic to the cyclopentadienyl
cation, these compounds are antiaromatic according to Hückel’s concept of aromaticity.[3]
Thiophene-based compounds have emerged as highly interesting, semiconducting
systems due to their tunable optical and electronical properties.[4] Our goal is the
syntheses of an array of multithiophene-functionalized borole systems (1) and the
investigation of their physical properties, with particular emphasis on the shapes and
energies of their frontier orbitals. Furthermore, our interest is also focused on boroles
serving as potential electron acceptors in push-pull systems (2), comparing them to other
well-established acceptor groups such as mesityl-substituted, three-coordinate boron
groups (-BMes2)(3).[5]
Bibliography
[1] J. J. Eisch, J. E. Galle, S. Kozima, J. Am. Chem. Soc. 1986, 108, 379–385.
[2] V. Gogonea, P. v R. Schleyer, P. R. Schreiner, Angew. Chem. Int. Ed. 1998, 37, 1945–
1948.
[3] M. K. Cyranski, T. M. Krygowski, A. R. Katritzky, P. v. R. Schleyer, J. Org. Chem. 2002,
67, 1333–1338.
[4] A. Mishra, P. Bäuerle, Angew. Chem. Int. Ed. 2012, 51, 2020–2067.
[5] Z. Yuan, C. D. Entwistle, J. C. Collings, D. Albesa-Jové, A. S. Batsanov, J. A. K. Howard,
N. J. Taylor, H. M. Kaiser, D. E. Kaufmann, S.-Y. Poon, W.-Y. Wong, C. Jardin, S.
Fathallah, A. Boucekkine, J.-F. Halet, T. B. Marder, Chem. Eur. 2006, 10, 2758-2771.
109
PP36 - Bonding Boron to Aromatic Metalation Synthetic Strategies
Jennifer Melanson and Victor Snieckus*
Boron plays a significant role in our synthetic programs. The conjunction of directed ortho
metalation (DoM) with the suzuki-miyaura cross coupling reaction has provided new
approaches to biaryl and heterobiaryl compounds [1]. This strategy has seen large-scale
pharmaceutical industry application (e.g. Losartan, BMS), and has led to directed remote
metalation (DreM) syntheses of fluorenones, phenanthrols, and bioactive heteroaromatics
and natural products [2]. We have also devised cross coupling reactions based on
directed metalation groups (DMGs) and recently have discovered new routes to biaryl and
heterobiaryl compounds via C-H [3] and C-O [4] activation routes. A selection of these
results with emphasis on the most recent chemistry will be presented.
Bibliography
[1] C. Schneider, E. Broda, V. Snieckus, Org. Lett. 2011, 13, 3588.
[2] J. Board, J.L. Cosman, T. Rantanen, S.P. Singh, V. Snieckus, Platinum Metals
Rev. 2013, 57, 234.
[3] T.E. Hurst, T.K. Macklin, M. Becker, E. Hartmann, W. Kügel, J.-C. Parisieene-La Salle,
A.S. Batsanov, T.B. Marder, V Snieckus, Chem. Eur. J. 2010, 16, 8155.
[4] Y. Zhao, V. Snieckus, Chem. Commun. 2016, 52, 1681.
110
PP37 - Catalysis for energy storage: Improved hydrogen release from
ammine metal borohydrides
Mehdi Mostajeran and R. Tom Baker*
Department of Chemistry and Biomolecular Sciences
Center for Catalysis Research and Innovation
University of Ottawa
Ottawa, ON, K1N 6N5, Canada
Emails: [email protected], [email protected]
Hydrogen has been introduced as a clean, renewable and sustainable energy source for the
future.[1] Its low volumetric storage capacity, however, has driven an intensive search for
efficient H2 storage materials.[2] Ammine metal borohydrides (AMBs, [M(BH4)m·nNH3]) [3]
have recently emerged as promising storage candidates with enhanced dehydrogenation
properties (i.e. lower H2 desorption temperature and absence of diborane by-product).[4] One
drawback of the current synthetic method for AMBs, ball-milling, is the retention of Li/NaCl in
the mixture. Therefore, more feasible synthetic methods for pure AMBs need to be
developed.[5] In this study, pure colorless crystals of Y(BH4)3(NH3)4 (AYB, 1) were
synthesized from condensing ammonia onto yellow crystals of Y(BH4)3·2thf (2) at -40°C
(confirmed by 11B MAS NMR spectroscopy and powder XRD). Thermolysis of 1 shows
simultaneous release of H2 and NH3 (Figure 1a). As most oxygen-based reductants react with
early metal borohydrides, we used an amine-borane reductant, n-hexylamine borane (HxAB),
for the synthesis of base-metal nanoparticles and to avoid insoluble contaminants.[6]
Compared to pure AYB, in which 7.7 wt.% hydrogen (95.0 mol% pure) was released upon
heat treatment from room temperature to 200 °C, AYB/CoNPs (Figures 1b and 1c) released
7.6 wt.% hydrogen (97.9 mol% pure) over the same temperature range. The catalyst caused
the exothermic peak appear at lower temperatures and the endothermic peak at 180 °C
converted to an exothermic event (Figure 1c).
Figure 1. TGA-MS data of Y(BH4)3(NH3)4 (a), Y(BH4)3(NH3)4/5 wt.% CoNPs (b) and DSC analysis of (a)
and (b) measured during heating from 25 to 200 °C under N2 with a heating ramp of 5 °C/min.
Bibliography
1. G. Cipriani, V. Di Dio, F. Genduso, D. La Cascia, R. Liga, R. Miceli, G. Ricco Galluzzo, Int. J.
Hydrogen Energy 2014, 39, 8482.
2. L. H. Jepsen, M. B. Ley, Y. –S. Lee, Y. W. Cho, M. Dornheim, J. O. Jensen, Y. Filinchuk, J. E.
Jørgensen, F. Besenbacher, T. R. Jensen, Mater. Today 2014, 17, 129.
3. Y. Song, F. Wu, X. Zheng, X. Ma, F. Fang, Y. Guo, Chem. Commun. 2015, 51, 1104.
4. C. Frommen, N. Aliouane, S. Deledda, J. E. Fonneløp, H. Grove, K. Lieutenant, I. Llamas-Jansa,
S. Sartori, M. H. Sørby, B. C. Hauback, J. Alloys Comp. 2010, 496, 710.
5. M. Mostajeran, D. J. Wolstenholme, C. Frazee, G. S. McGrady, R. T. Baker, Chem Commun 2016,
52, 2851.
6. N. Zheng, J. Fan, G. D. Stucky, J. Am. Chem. Soc. 2006, 128, 6550.
111
PP38 - Iron-Catalyzed Diboration, Carboboration, and Carbo-silation of
Alkynes
Naohisa Nakagawa, Tatsushi Nishikori, Takuji Hatakeyama, Iwamoto Takahiro, and
Masaharu Nakamura
International Research Center of Elements Science （IRCELS）
Institute for Chemical Research, Kyoto University
Gokasho, Uji, Kyoto, 611-0011 Japan. Email: [email protected]
Alkenylboron compounds are key intermediates for the synthesis of a wide range of
functional molecules, such as electronic materials and bioacitve natural products. In
particluare, diborylalkenes are attractive building blocks for construction of π-extended
conjugated molecular frameworks. Transition-metal-catalyzed diboration of alkynes have
thus been investigated intensively and extensively and various transition metals, such as
platinum, cobalt, iridium, copper, and gold have been reported as catalysts of the
diboration of alkynes. We have found that a simple iron salt can catalyze the diboration of
alkynes in a highly stereoselective to give the corresponding 1,2-diboryl alkene in good to
excellent yields (eq 1). In addition, the present catalyst system is amenable to in situ
trapping with unactivated alkyl halides to furnish a wide array of alkenyl boron compounds
as a single geometrical isomer (eq 2). When silylboron reagent is used, anti-selective
carbosilation proceeds in the presence of an iron salt and dppe ligand (eq 3).
Reference
"Iron-Catalyzed Diboration and Carboboration of Alkynes" Nakagawa, N.; Hatakeyama, T.;
Nakamura, M. Chem. Eur. J. 2015, 21, 4257-4261. Highlighted in SYNFACTS, 2015, 0418.
112
PP39 - Synthesis and Characterization of Boron Difluoride
Formazanate Polymers
Samantha Novoa, Stephanie Barbon and Joe B. Gilroy*
Department of Chemistry and the Centre for Advanced Materials
and Biomaterials Research (CAMBR)
E-mails: [email protected], [email protected]
Boron difluoride (BF2) formazanate complexes have been shown to possess interesting
tunable spectroscopic properties, moderate to high fluorescence quantum yields, and
unusual redox activity.[1] Their incorporation into side chain polymers (e.g., 1) through ringopening metathesis polymerization (ROMP) preserved the unique properties of the
complex, and mechanistic studies showed the controlled nature of the polymerization.[2]
Furthermore, main-chain copolymers based on BF2 complexes and fluorene derivatives
(e.g., 2) were synthesized by alkyne-azide cycloaddition. These copolymers exhibited a
red-shift in their absorption and emission spectra due to the extended π conjugation
associated with the triazole rings. Both the main-chain and side-chain BF2 formazanate
polymers show potential as light-harvesting materials. Recent results surrounding the
synthesis, characterization, and materials-based applications of BF2 formazanate polymers
will be presented.
Bibliography
[1] S. M. Barbon, J. T. Price, P. A. Reinkeluers, J. B. Gilroy, Inorg. Chem. 2014, 53,
10585–10593.
[2] S. Novoa, J. A. Paquette, S. M. Barbon, R. R. Maar, J.B. Gilroy, J. Mater. Chem. C.
2016, 4, DOI: 10.1039/C5TC03287C.
113
PP40 - Synthesis of Fluorescent Boron-Nitrogen Containing Indenes
via Zirconocene Intermediates
Evan A. Patrick, Matthew M. Morgan, Denis Spasyuk, and Warren E. Piers*
University of Calgary
Calgary, AB, T2N 1N4, Canada
Email: [email protected], [email protected]*
Due to their conductive characteristics, polycyclic aromatic hydrocarbons have been used
extensively in materials such as organic light emitting diodes [1], organic field effect
transistors [2], and organic photovoltaics [3,4]. The introduction of heteroatoms to these
frameworks has offered a method to tune the energy levels of these materials for their
respective applications. A particularly useful substitution is the B-N moiety due to its
isoelectronic and isosteric relationship with C-C bonds. Synthetically, this has been
achieved in a variety of different ways, most predominantly through ring-closing metathesis
or electrophilic borylation reactions [5]. In previous work from our group, the borole
derivative 1,2,3-tris(pentafluorophenyl)-4,5,6,7-tetrafluoro-1-boraindene was synthesized
using a zirconocene metallocycle intermediate [6]. Separately, the Jordan group has been
able to obtain similar metallocycles via a sigma-bond metathesis reaction with pyridine
derivatives [7]. By combining these previously established pathways, we have been able to
produce a new synthetic route to boron-nitrogen containing indene compounds. This
presentation will detail two variations of this synthesis to yield the the (E)-2-(2(chloro(phenyl)boryl)-1,2-diphenylvinyl)pyridine, and some chemical reactivity of this
product.
Bibliography
[1] X. Wang, F. Zhang, J. Liu, R. Tang, Y. Fu, D. Wu, Q. Xu, X. Zhuang, G. He, X. Feng,
Org. Lett. 2013, 15 (22), 5714.
[2] X.-Y. Wang, H.-R. Lin, T. Lei, D.-C. Yang, F.-D. Zhuang, J.-Y. Wang, S.-C. Yuan, J. Pei,
Angew. Chem. 2013, 125 (11), 3199.
[3] Y. Shu, Y.-F. Lim, Z. Li, B. Purushothaman, R. Hallani, J. E. Kim, S. R. Parkin, G. G.
Malliaras, J. E. Anthony, Chem Sci 2011, 2 (2), 363. [4] A. A. Gorodetsky, M. Cox, N. J. Tremblay, I. Kymissis, C. Nuckolls, Chem. Mater. 2009,
21 (18), 4090. [5] M. M. Morgan, W. E. Piers, Dalton Trans 2016, 45, 5920.
[6] A. Y. Houghton, V. A. Karttunen, W. E. Piers, H. M. Tuononen, Chem Commun 2014,
50 (11), 1295.
[7] F. Wu, R. F. Jordan, Organometallics 2005, 24 (11), 2688.
114
PP41 - Chemo-, Regio-, and Stereoselective Copper(II)-Catalyzed Boron
Addition to Acetylenic Esters and Amides in Aqueous Media
Cheryl L. Peck, Amanda K. Nelson, Sean M. Rafferty, and Webster
L. Santos*
Virginia Tech
Blacksburg, VA 24061
Vinylboronic acids and their derivatives serve as values intermediates in organic synthesis,
therefore, the development of simple, efficient, and sustainable methods for their
installation is vital. Among the countless protecting groups for boron, the pinacol (pin)
moiety is frequently used due to its reactivity and compatibility with numerous reaction
conditions. However, the 1,8-diamononaphthyl group (dan) is emerging as an orthogonal
protecting group. This moiety is attractive due to its robustness and ability to fine-tune the
reactivity of the boron center.
Our lab previously established a copper(II)-catalyzed aqueous borylation protocol of
ethylenic esters and ketones using the symmetrical diboron reagent, B2pin2.[1] This
procedure was further extended to incorporate acetylenic esters.[2] Unfortunately, only a
single multistep protocol to incorporate Bdan onto the vinylic β-carbon of esters has been
established.[3] Given our interest in developing sustainable borylation methods and the
scarcity of borylation reactions conducted in water, we developed an efficient and
environmentally friendly process for the addition of Bdan to acetylenic carbonyl groups
using an unsymmetrical diboron reagent.[4] In this strategy, we capitalized on the
chemoselective activation of the more Lewis acidic boron by activating Bpin with a Lewis
base to form an sp2-sp3 diboron intermediate thereby facilitating the transfer of Bdan. The
structurally diverse 1,8-diaminonapthalene protected β-boryl-α,β-unsaturated carbonyl
compounds were generated in moderate to high yields and in excellent stereoselectivity.
Bibliography
[1] Thorpe, S.B.; Calderone, J. A.; Santos, W. L. Org. Lett. 2012, 14, 1918.
[2] Peck, C.L.; Calderone, J.A.; Santos, W.L. Synthesis 2015, 47, 2242.
[3] Gravel, M.; Touré, B.B.; Hall, D.G. Org. Prep. Proced. Int. 2004, 36, 573.
[4] Nelson, A.K.; Peck, C.L.; Rafferty, S.M.; Santos, W.L. J. Org. Chem. 2016, DOI:
10.1021/acs.joc.6b00648.
115
PP42 - Synthesis and Reactivity of Chloroallylboronates
Pjotr C. Roest, Robert A. Batey*
The chloroallylation of carbonyl compounds represents a powerful method for the
synthesis of chlorinated natural products. Despite the ubiquity of allylboron reagents for
stereoselective allylation reactions, chloroallylboron reagents remain relatively difficult to
access. We have developed a short and scalable route to both the (E) and (Z) isomers of
chloroallylboronic acid pinacol ester, as well as substituted derivatives thereof.
Furthermore, the utility of the corresponding potassium trifluoroborate salts in the
stereoselective chloroallylation of aldehydes and ketones has been demonstrated.
116
PP43 – Iterative, Protecting Group Free Suzuki-Miyaura Coupling of
Enantioenriched Polyboronates
Christopher Ziebenhaus, Jason P. G. Rygus, Kazem Ghozati, Philip J. Unsworth,
Masakuza Nambo, Samantha Voth, Yuuki Maekawa, Cathleen M. Crudden*
The Suzuki-Miyaura cross-coupling is one of the most widely used reactions in chemical
synthesis in both laboratory and industrial settings. In particular, it has found wide
applicability in the construction of biaryl or polyene scaffolds, and has been proposed as
the key reaction for the modular, automated assembly of such structural motifs through
iterative reactions1. Such a process relies on the use of protecting groups to modulate the
activity of various C-B bonds, and thus requires costly, inefficient protection and
deprotection steps for each bond forming sequence. Herein we describe a significant
advancement in the field of iterative cross-coupling of polyborylated substrates containing
aromatic, primary aliphatic and secondary benzylic C-B bonds2 to generate
enantioenriched, multiply arylated structures without the use of boron protecting groups.
We demonstrate chemoselective cross-coupling based solely on the intrinsic differences in
reactivity imparted by the nature of the C-B bond. The synthesis of a biologically active
compound will be highlighted. In addition, preliminary investigations into the loss of optical
activity during the secondary benzylic cross-coupling will be discussed.
1
Woerly E.M., Roy J. & Burke M.D., Nature Chem. 2014, 6, 484
Imao D., Glasspoole B.W., Laberge V.S. & Crudden C.M. J. Am. Chem. Soc. 2009, 131,
5024
3
Crudden C.M., Ziebenhaus C., Rygus J.P.G., Ghozati K., Unsworth P.J., Nambo M., Voth
S., Hutchinson M., Laberge V.S., Maekawa Y. & Imao D. Nature Communications, 2016, 7,
11065
2
117
PP44 - The Organometallic Chemistry of Carboranes
Liban M. A. Saleh, Rafal M. Dziedzic, Simone Stevens, Saeed I. Khan, Arnold L.
Rheingold and Alexander M. Spokoyny*
Los Angeles, CA 90024, U.S.A
Icosahedral carboranes are robust, boron-rich molecules with unique structural and
electronic properties [1]. They are often thought of as 3D aromatic analogues of aryl
groups, and substitution at carbon and boron vertices make them attractive precursors for
a variety of applications [2]. However, compared to traditional aromatic hydrocarbon
chemistry, carborane boron vertex substitution is relatively underdeveloped [3]. Our
laboratory is interested in the fundamental chemistry of these molecules, their preparation,
and their use for building functional materials. Here, we report our recent studies into the
functionalization of these species [4, 5].
We are currently investigating metal-catalyzed cross-coupling routes for Bfunctionalization of carboranes. We will highlight a new route to constructing metalboron bonds to aid understanding of the elementary steps of cross-coupling
involving carboranes [4]. We will further demonstrate how the use of different
halocarborane coupling partners can allow facile installation of previously
inaccessible functional groups [5].
Bibliography
[1] R. N. Grimes, Carboranes, Academic Press, London, 2nd Ed., 2011.
[2] A. M. Spokoyny, Pure and Appl. Chem., 2013, 85, 903; D. Olid et. al., Chem. Soc. Rev.,
2013, 42, 3318; Z. Qui, Tetrahedron Lett., 2015, 56, 963
[3] For examples see: J. Li et. al., Inorg. Chem., 1991, 30, 4866; Z. Zheng et. al., Inorg.
Chem., 1995, 34, 2095; W. Jiang Z. Zheng et. al., Inorg. Chem., 1995, 34, 3491; C. Viñas et.
al., Inorg. Chem., 2001, 40, 6555; Y. Quan and Z. Xie, Angew. Chem., Int. Ed., 2016, 55,
1295.
[4] L. M. A. Saleh, R. M. Dziedzic, S. I. Khan and A. M. Spokoyny, submitted.
[5] R. M. Dziedzic, L. M. A. Saleh, S. Stevens, A. L. Rheingold and A. M. Spokoyny,
submitted.
118
PP45 - Raman spectroscopy as a tool for detection of boroncompounds in specific areas of the central nervous system
Julia J. Segura-Uribe, Maribel Pérez Rodríguez, Paola García-De la
Torre, Christian H. Guerra-Araiza, José G. Trujillo-Ferrara, Marvin A.
Soriano-Ursúa*
Department of Physiology,
Escuela Superior de Medicina-IPN
Mexico City, 11340, Mexico
It has been suggested that when functional groups with boron atoms are added to wellknown drugs, the latter are conferred with greater potency and efficacy on their target
receptors [1]. The use of boronic acid, boronate ester and boroxole functional groups in
chemical biology and medicinal chemistry has increased intensely in recent years. These
moieties have many advantages, among these, boronic acids form strong, reversible
covalent bonds to target diols [2]. The boron-containing groups themselves have low
toxicity and therefore may be incorporated into molecules, such as peptides, without
notable cytotoxic side effects [3]. Both, researchers and the pharmaceutical industry are
showing an increasing interest in boron as an alternative to carbon in drug design [4, 5].
Raman spectroscopy is a photometric technique that allows identifying molecules and
compounds in biological samples. It has been used as a tool to identify the composition of
different areas in the central nervous system (CNS) [6]. Due to the different chemical
composition of specific areas of the brain, it is important to determine which of these areas
interact with boron-compounds, and to determine if these compounds have biological
effects [1]. Some of these boron-compounds, such as cyclopentyl/thienyl/furanyl/phenylboronic acids, were administered to mice to determine their acute toxicity and availability
through the CNS. Afterwards, Raman spectrum of specific areas, such as frontal cortex,
substancia nigra, spinal bulb and cerebellum, were obtained and analyzed to identify the
presence of the boron-compounds signal as well as the possible intermolecular
interactions found in each CNS-area.
Bibliography
[1] M.A. Soriano-Ursúa, E.D. Farfán-García, Y. López-Cabrera, et al. NeuroToxicology. 2014, 40, 8.
[2] G.F. Whyte, R. Vilar, R. Wolschoski, J. Chem. Biol. 2013, 6, 161.
[3] P. Hunter, EMBO. Reports. 2009, 10, 125.
[4] S. J. Baker, C. Z. Ding, T. Akama, et al., Future. Med. Chem. 2009, 1, 1275.
[5] P. V. Ramachandran, Future. Med. Chem. 2013, 5, 611.
[6] M. Daković, A. S. Stojiljković, D. Bajuk-Bogdanović, et al., Talanta. 2013, 117, 133.
119
PP46 - D-A-D Type Organic Dyes Using BF2-Bridged
Dipyrrolylethanedione as an Electron-Accepting Unit
Hiroyuki Shimogawa, Atsushi Wakamiya,* Yasujiro Murata*
Institute for Chemical Research
Kyoto University
Uji, Kyoto 611-0011, Japan
Boron-bridged heteroatom-containing π-conjugated skeletons have unique photophysical
and electrochemical properties base don the electronic effects of intramolecular Bheteroatom coordination bond formation. We designed a doubly BF2-bridged
dipyrrolylethanedione as a new type of boron-bridged π-conjugated skeleton (Figure 1a).
As the model compound, dimesityl-substituted derivative 1 was synthesized. X-ray
structrual analysis of 1 shows the dipyrrolylethanedione moiety had highly planar structure
with large bond alternation, indicating the larger contribution of π-conjugation mode as
azafulvene dimer than that as dipyrrolylethanedione (Figure 2). Owing to the synergy
effects of the large contribution of the π-conjugation mode as azafulvene dimer and
intramolecular B-N coordination bonds formation, 1 shows reversible reduction waves at 0.50 and -1.05 V (vs. Fc/Fc+) in cyclic voltammetry, indicating high electron-accepting
ability of BF2-bridged dipyrrolylethanedione skeleton. Then, using this skeleton as an
electron-accepting unit, D-A-D type compound 2 with di(4-hexyloxyphenyl)aminothienyl
units as electron donating groups was synthesized. In CV, D-A-D type compound 2 shows
reversible reduction and oxidation waves at -0.78 and 0.21 V, respectively. Owing to the
narrow HOMO-LUMO gap, 2 exhibits an intense absorption band at λ = 922 nm (ϵ =
116,000 M-1 cm-1), which is red-shifted by 442 nm compared with that of 1 (λ = 480 nm (ϵ =
31,500 M-1 cm-1)), accompanied with increase of the extinction coefficient (Figure 3). In this
presentation, the details of synthesis and properties of these compounds will be
presented.
a)
F
F
O
R
N
F B
F
1 : R = Mesityl
B F
N
O
R
OC6H13
B
2: R =
N
O
B
F
N
N
B O
Figure 1. (a) Structures of 1–2 and (b) ORTEP
drawing of 1.
e / 10 4 M –1 cm –1
b)
F
O
O
R
F
B
N
R
N
R
B
F
O
F
Figure 2. Resonance structures of 1.
12
OC6H13
F
N
R
F
S
B
N
O
F
F
––– 1
––– 2
10
8
6
4
2
0
300 400
500 600 700 800 900 1000 1100 1200
Wavelength / nm
Figure 3. UV/vis/NIR absorption spectra of 1–2 in CH2Cl2.
120
PP47 - Transition Metal-Free trans-Diboration of Alkynamides with an
Unsymmetrical Diboron Reagent
Russell F. Snead, Astha Verma, Yumin Dai, Brett Rastatter,
and Webster L. Santos*
Virginia Tech
Blacksburg, VA
Metal-free and environmentally-friendly methods for borylation of C-C double bonds are in
high demand due to the synthetic versatility of the resulting organoboron compounds [1,2].
Building on previous results from our lab which demonstrate metal-free borylation of
alkynoic acids [3], we have developed a methodology for regio- and stereoselective
diboration of alkynamides using the unsymmetrical and differentially-protected diboron
reagent, pinB-Bdan. The proposed reaction mechanism, which has been corroborated by
DFT studies, involves activation of the diboron reagent by the deprotonated alkynamide
followed by two subsequent borylation steps through 5-membered cyclic transition states.
This process provides an environmentally-friendly protocol to synthesize uncommon (E)diborated alkenes. Since these products bear two boron moieties with different protecting
groups, sequential, regioselective cross-coupling reactions can be achieved to produce
valuable tetra-substituted alkenes. Good yields are observed with use of N-methyl aryl
propiolamides bearing electron-withdrawing, electron-donating, and ortho-substituents on
the aromatic ring.
Bibliography
[1] Qiao, J. X.; Lam, P. Y. S., Synthesis 2011, 2011, 829-856;
[2] Miyaura, N.; Suzuki, A., Chem. Rev. 1995, 95, 2457-2483.
[3] Verma, A.; Rastatter, B.; Santos, W. L. 2016, In Preparation.
121
PP48 - Selective saccharide sensor by boronic acid-modified
poly(amidoamine) dendrimer
Ching-Hua Tsai, Chai-Lin Kao*
Medicinal and Applied Chemistry
Kaohsiung Medical University
Kaohsiung City807, Taiwan
The dynamic covalent bonds between boronic acid and diols empowers boronic acid
binding saccharides capacities. Therefore, it have been used in delivery target and analyst
field. However, this system not generally used in dendrimers. Several obstacles have been
identified, such as low introduction rate, no suitable analytic tool. Herein, we reported our
recent effort in the preparation of boron acid-modified dendrimers as selectively
saccharides sensor and identification by displacement fluorescence detection and NMR
and ICP-MS. Therefore, we prepared (G:2~6)-dendri-PAMAM-(CPBA)n (CPBA: 4carboxyphenylboronic acid). In the fluorescence experiment, we used characteristic of
Alizarin Red S (ARS) binding with boronic acid product fluorescence to identify binding
affinity between dendrimers and saccharides. All dendrimers sensors binding with ARS
displayed decrease fluorescence intensity upon the addition of those saccharides, those
dendrimers sensor showing higher selectivity for D-glucose over D-galactose, D-fructose
and D-lactose. In this investigation, size-dependent binding ability and positive dendritic
effect was observed and identified. Their binding with various saccharides was measured
through competition experiments with ARS. Binding affinity was analyzed by Benesi Hildebrand equation. The result show clear selectivity among various carbohydrates. The
detail of preparation and result of analysis will be presented.
122
PP49 - Borylative Cyclisation of Alkynes Using BCl3
Andrew J. Warner, James R. Lawson, Valerio Fasano, Anna Churn, Michael J.
Ingleson*
Oxford Road, Manchester, M13 9PL
C(sp2)-boronic acid and ester derivatives are ubiquitous in modern synthetic chemistry due
to their good ambient stability, low toxicity, utility in C-C bond formation and facile
transformation into other important functional groups.[1] However, the installation of boronic
acid derivatives classically require Grignard or organolithium reagents, which suffer from
compatibility issues and necessitate cryogenic temperatures,[2] although powerful methods
have been developed to carry out direct C-H borylation using transition metal catalysts.[3]
Electrophilic borylation,[4] carbanion mediated borylation,[5] and electrophilic oxyboration[6]
are alternative methodologies that provide access to borylated compounds, whilst
circumventing the necessity for transition metal catalysts. The work presented herein
highlights an efficient and facile methodology which utilises the inexpensive boron
electrophile, BCl3, to achieve concomitant cyclisation and borylation, termed borylative
cyclisation. Depending on the starting alkyne, the reaction proceeds via an electrophilic
aromatic substitution (Scheme 1, top) or a heteroatomic nucleophilic attack (Scheme 1,
bottom) on the boron activated alkyne, forming new C-C/C-Y and C-B bonds, generating
highly functionalisable borylated cyclic products rapidly under ambient conditions. These
cyclic scaffolds are highly prevalent in biologically and pharmacologically active molecules
making borylative cyclisation an attractive route for the synthesis of libraries of these
compounds.
Scheme 1. Borylative cyclisation of internal alkynes using BCl3.
[1] N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457
[2] D. Hall, Ed. Boronic Acids: Preparation and Applications, Wiley-VCH, 2011
[3] I. A. I. Mkhalid, J. H. Barnard, T. B. Marder, J. M. Murphy, J. F. Hartwig, Chem. Rev. 2010,
110, 890
[4] M. J. Ingleson, Top. Organomet. Chem. 2015, 49, 39.
[5] E. Yamamoto, K. Izumi, Y. Horita, H. Ito, J. Am. Chem. Soc. 2012, 134, 19997;
[6] D. J. Faizi; A. Issaian; A. J. Davis; S. A. Blum, J. Am. Chem. Soc. 2016, 138, 2126
123
PP50 – Metal-Mediated Synthesis of Azaborinines and Reactivities of
Iminoboranes with Carbenes
Lena Winner, Marius Schäfer, Holger Braunschweig*
The well-known isoelectronic relationship between C≡C and B≡N triple bonds has been in
the focus of strategies aimed at the diversification of molecules relevant to materials
science and biomedical research. Recently, we reported the synthesis of the first nonbenzo-fused 1,4-di-tert-butyl-azaborinine, as well as the first ferrocene-functionalized
azaborinine 1,2-di-tert-butyl-4,6-diferrocenyl-1,2-azaborinine, through tandem rhodiumcatalyzed [2+2]/[2+4] cycloaddition reactions. In order to investigate the synthetic scope of
this method we reacted the isolated intermediates, that is the rhodium ƞ4-1,2-azaborete
complexes 1 and 2, with acetylene, leading to the isolation of 1,4-di-tert-butyl-2-phenyl-1,4azaborinine (3) and 1,4-di-tert-butyl-2-ferrocenyl-1,4-azaborinine (4). The key results of
this work will be described. The scope of this chemistry has been extended using a bulky
novel iminoborane, developed in our group, in reactions yielding new 1,2-azaborete
rhodium complexes and new azaborinines. We have also prepared and structurally
characterized examples of a heretofore unknown class of iminoborane–carbene adducts,
as well as a new BN-functionalized carbene.
3
4
3
Bibliography
[1] Z. Liu, T. B. Marder, Angew. Chem. 2008, 120, 248-250.
[2] H. Braunschweig, A. Damme, J. O. C. Jimenez-Halla, B. Pfaffinger, K. Radacki, J. Wolf,
Angew. Chem. 2012, 124, 10177-10180.
[3] H. Braunschweig, K. Geetharani, J. O. C. Jimenez-Halla, M. Schäfer, Angew. Chem.
2014, 126, 3568-3572.
[4] H. Braunschweig, W. C. Ewing, K. Geetharani, and M. Schäfer, Angew. Chem. Int. Ed.
2015, 54, 1662 –1665.
124
PP51 - Controlling Molecular Transformations of BN-Heterocycles:
Photoisomerization vs Photoelimination
Deng-Tao Yang, Suning Wang*
New and unusual photo/thermal transformations which can be exploited for the
construction of unique organoboron-based functional materials have gained significant
research attention.[1-4] One of our key research directions involves discovering and
examining new reactivities of BN-heterocycles imparted by external stimuli such as light or
heat. Previously, we have shown that BN-heterocycles bearing either a five or six
membered ring BN-core display vastly different responses upon exposure to light, such as
multi-step isomerizations or mesitylene elimination respectively. In terms of the latter, the
elimination reaction affords highly emissive azaborine products which can be achieved
through a variety of different stimuli such as light, heat, or even excitons with organic light
emitting diode (OLED) devices.[4] This presentation will focus on our latest findings which
show that by controlling the electronic structure of the boryl unit within six-membered BNheterocycles, their reactivity can be completely tuned in favour of an unprecedented
photochromic pathway involving the formation of an eight-membered ring dark isomer (C).
Insight into this new transformation and their implications will be discussed.
Bibliography
[1] Y. L. Rao, H. Amarne, S. Wang, Coord. Chem. Rev., 2012, 256, 759.
[2] A. Lida, S. Saito, T. Sasamori, S. Yamaguchi, Angew. Chem. Int. Ed. 2013, 52, 3760.
[3] Y. L. Rao, H. Amarne, L. D. Chen, N. J. Mosey, S. Wang, J. Am. Chem. Soc. 2013, 135,
3407.
[4] S. Wang et al, Angew. Chem. Int. Ed. 2013, 52, 4544; Angew. Chem. Int. Ed. 2015, 54,
5498; Angew. Chem. Int. Ed. 2015, 54, 15074.
125
PP52 - Preparation and Characterization of Spiro Bicyclic B,N-chelate
Compounds
Kang Yuan, Suning Wang*
The synthesis of B,N-containing heterocycles has been of longstanding interest due to
their interesting photophysical properties and unique reactivities. Earlier work in the
Wang’s group has shown five-membered B,N-heterocycles can display intriguing
photochromism.1 Yamaguchi and others have demonstrated that B,N-embedded πconjugated systems display intense fluorescence and can act as electron-transporting
materials in organic electronic devices.2 Another popular class of B,N-heterocycles are
boron-dipyrromethenes, which have attracted enormous recent attention as a result of
their rich optoelectronic properties.3
Spiro bicyclic systems4 (e.g. spirofluorene) with two perpendicular π-systems are known to
exhibit many useful properties such as good carrier injection/transport ability or strong
electroluminescence in the solid state due to their unique structural features. In this
presentation, I will present the synthesis of spiro bicyclic B,N-chelate compounds as well
as the investigation of their photophysical properties.
Bibliography
[1] Y. L. Rao, H. Amarne, S. Wang, Coord. Chem. Rev., 2012, 256, 759.
[2] Wakamiya, A.; Yamaguchi, S. Bull. Chem. Soc. Jpn., 2015, 88, 1357.
[3] A. Loudet, K. Burgess, Chem. Rev., 2007, 107, 4891.
[4] D. L. Crossley, J. Cid, L. D. Curless, M. L. Turner, M. J. Ingleson, Organometallics, 2015,
34, 5767.
126
PP53 - Eight Membered Dimetallaheterocycles: Main Group-Transition
Metal Analogues of 1,5-Cyclooctadiene
K. Yuvaraj, V. Ramkumar, Sundargopal Ghosh*
Metalla-aromatics are analogues of organic molecules that can be derived from the formal
replacement of carbon segment by isolobal transition-metal fragment. [1] One of the most
interesting aspects in metalla-aromatics is to understand both electronic and requirement
of the metal to attain aromaticity. Although the existences of these compounds were first
proposed by Thorn and Hoffmann in 1979, [2] synthetic methods to construct stable
metalla-aromatics are very limited. As part of our current interest in the synthesis of
electron-precise transition metal boron complexes, [3] we have recently reported a number
of agostic σ-borane/borate complexes of ruthenium, rhodium, iridium and molybdenum
using different synthetic approaches. [4] This presentation will focus on our recent findings
on the eight membered dimetallaheterocycles [(Mcod)2(bt)2], (M = Ir and Rh) and a borate
complex [Rh(cod){κ2-S,S′-H2B(bt)2}]. Ruthenium system offered the agostic complexes
[Ru(cod)L{κ3-H,S,S′-H2B(bt)2}], (L = Cl; C7H4NS2). Further, the electronic structure and
bonding of these novel complexes have been established on the ground of DFT. Key
results of this work will be described.
Bibliography
[1] J. R. Bleeke, Acc. Chem. Res. 2007, 40, 1035.
[2] D. L. Thorn, R. Hoffman, Nouv. J. Chim. 1979, 3, 39.
[3] a) G. R. Owen, Chem. Soc. Rev. 2012, 41, 3535; b) J. R. Bleeke, Chem. Rev. 2001, 101,
1205; c) H. Braunschweig, R. D. Dewhurst, A. Schneider, Chem. Rev. 2010, 110, 3924.
[4] a) R. S. Anju, D. K. Roy, B. Mondal, K. Yuvaraj, C. Arivazhagan, K. Saha, B. Varghese, S.
Ghosh, Angew. Chem. Int. Ed. 2014, 53, 2873; b) R. Ramalakshmi, K. Saha, D. K. Roy, B.
Varghese, A. K. Phukan, S. Ghosh, Chem. Eur. J. 2015, 21, 17191.
127
PP54 - Incorporation of polycyclic azaborine compounds into
polythiophene-type conjugated polymers for organic field-eﬀect
transistors
Xiao-Ye Wang, Fang-Dong Zhuang, Jie-Yu Wang*, Jian Pei*
Laboratory for Molecular Materials,
College of Chemistry and Molecular Engineering,
Peking University, Beijing 100080, China
Email: [email protected], [email protected],
[email protected]
Recently, azaborine chemistry, which employs a B–N bond as a substitute for the C=C
bond in benzene rings, has attracted great interest due to its fundamental importance in
the understanding of aromaticity and potential applications in hydrogen storage and
biomedical research.1 Meanwhile, the BN substitution strategy in polycyclic
aromaticsystems has provideda number of interesting compounds with modified
optoelectronic properties and intermolecular interactions.2 These advances have triggered
the research on polycyclic azaborine compounds for electronic device. Herein, we develop
a BN-substituted tetrathienonaphthalene (BNTTN) monomer to construct the first
azaborine-based conjugated polymers for organic electronics, which exhibited low HOMO
levels and strong intermolecular interactions, leading to a hole mobility of up to 0.38 cm 2V1 -1
s .
Reference:
1. For reviews,see: (a)X.-Y. Wang, J.-Y. Wang and J. Pei, Chem. –Eur. J., 2015, 21,
3528; (b) P. G. Campbell, A. J. V. Marwitz and S. Y. Liu, Angew. Chem. Int. Ed., 2012,
51, 6074; (c) M. J. D. Bosdet and W. E. Piers, Can. J. Chem., 2009, 87, 8;
2. (a) M. J. D. Bosdet, W. E. Piers, T. S. Sorensen and M. Parvez, Angew. Chem., Int.
Ed., 2007, 46, 4940; (b) B. Neue, J. F. Araneda, W. E. Piers and M. Parvez, Angew.
Chem., Int. Ed., 2013, 52, 9966; (c) M. Lepeltier, O. Lukoyanova, A. Jacobson, S.
Jeeva and D. F. Perepichka, Chem. Commun., 2010, 46, 7007;
128
PP55 - Diverging Pathways in the Activation of Allenes with Lewis
Acids and Bases: Addition, 1,2-Carboboration and Cyclisation.
Lewis C. Wilkins, Rebecca L. Melen,*
School of Chemistry, Cardiff University, Main Building, Cardiff CF10 3AT, Cymru/Wales, UK.
The chemistry of frustrated Lewis pairs (FLPs) has exploded since their first report in
2006.[1] FLPs have also been shown to effect 1,2-additions to both alkynes and alkenes. In
the last few years, the Erker group extended the use of boron Lewis acids in various
carboboration reactions utilising the strong Lewis acids B(C6F5)3 or RB(C6F5)2 to generate
alkenylboranes from terminal and internal alkynes.[2]
The treatment of allenyl ketones or esters with (frustrated) Lewis acid-base pairs
results in the nucleophilic attack of the phosphine to the β-carbon due to σactivation of the ketone by the Lewis acidic boron. In the absence of an external
Lewis base, σ-activation triggers a 1,2-carboboration mechanism yielding a 6membered heterocyclic species with a chelating boron.[3] In the presence of water
the formation of γ-lactone products could be observed which is reminiscent of
reactivity typically observed with π-Lewis acidic transition metals.[4] It is noted that
the 1,2-carboboration products of the reactions with B(C6F5)3 generate organoboron
compounds, which might have further applications in organic synthesis.[5]
References
1. G. C. Welch, R. R. San Juan, J. D. Masuda, D. W. Stephan, Science 2006, 314, 1124-
1126.
2. G. Kehr, G. Erker, Chem. Commun. 2012, 48, 1839-1850
3. R. L. Melen, L. C. Wilkins, B. M. Kariuki, H. Wadepohl, L. H. Gade, A. S. K. Hashmi, D.
W. Stephan, M. M. Hansmann, Organometallics, 2015, 34, 4127
4. L. -P. Liu, B. Xu, M. S. Mashuta, G. B. Hammond, J. Am. Chem. Soc. 2008, 130,
17642-17643
5. Okuno, Y.; Yamashita, M.; Nozaki, K. Angew. Chem., Int. Ed. 2011, 50, 920-923.
129
BORAM XV Attendees
Name
Affiliation
Email
Antonio Abad-García
[email protected]
Naoki Ando
Nagoya University
[email protected]
Zachary Ariki
Queen's University
[email protected]
C. Arivazhagan
[email protected]
Merle Arrowsmith
[email protected]
Dominic Auerhammer
[email protected]
Pam Bandy-Dofoe
Queen's University
[email protected]
Stephanie Barbon
University of Western Ontario
[email protected]
Nurcan Baser-Kirazli
Rutgers University
[email protected]
Alexander Benziger
[email protected]
Hridaynath Bhattacharjee
University of Saskatchewan
[email protected]
Moulika Bhattacharyya
[email protected]
Julian Böhnke
[email protected]
Yuri Bolshan
[email protected]
Jessica Bouchard
Pearson Caanda
[email protected]
Nicolas Bouchard
Laval University
[email protected]
Jeremy L. Bourque
[email protected]
Beth Bosley
Boron Specialties LLC
[email protected]
Holger Braunschweig
[email protected]
Megan Bruce
Queen's University
[email protected]
Esmeralda Bukuroshi
[email protected]
Levy L. Cao
[email protected]
Xue-Nian Chen
Henan Normal University
[email protected]
Fuyong Cheng
National Research Council Canada
[email protected]
Edward Cieplechowicz
Queen's University
[email protected]
Joshua Clarke
Queen's University
[email protected]
Thomas Cole
[email protected]
Daniel Crossley
[email protected]
Cathleen Crudden
Queen's University
[email protected]
John Cullen
Queen's University
[email protected]
Dennis Curran
University of Pittsburg
Lauren Daley
Kyan D'Angelo
[email protected]
[email protected]
[email protected]
Bhaskar C. Das
University of Kansas
[email protected]
Uttam Das
[email protected]
Andrea Deißenberger
[email protected]
Theresa Dellerman
[email protected]
Victoria Dimakos
[email protected]
Rebecca Dominguez
[email protected]
Joel Dopke
Alma College
Patrick Eisenberger
[email protected]
Gerhard Erker
Universität Münster
[email protected]
William Ewing
Boron Specialties
[email protected]
Louie Fan
[email protected]
Valerio Fasano
[email protected]
Debra Feakes
[email protected]
Kayla Fisher
[email protected]
Sundargopal Ghosh
IIT Madras
[email protected]
Lisa Gomes Le Yang
MilliporeSigma
[email protected]
[email protected]
130
Stefanie Griesbeck
[email protected]
Jingwen Guan
National Research Council of Canada
[email protected]
Sahaj Gupta
Queen's University
[email protected]
Dennis Hall
University of Alberta
[email protected]
Dylan Harris
[email protected]
Devon P. Holst
[email protected]
Michael Ingleson
[email protected]
Frieder Jäkle
Rutgers University
[email protected]
Trevor Janes
[email protected]
Paul Jelliss
[email protected]
R. Bruce King
Univeristy of Georgia
[email protected]
Lucas Kuzmanic
[email protected]
Emmanuel Lacote
CNRS
[email protected]
Jolie Lam
[email protected]
Anthony D. Ledet
Mark Lee
University of Missouri
[email protected]
Julien Légaré-Lavergne
Laval University
[email protected]
Cathy Li
Allychem
[email protected]
Haijun Li
Queen's University
[email protected]
Yufei Li
Northernchem Inc
[email protected]
Yi Li
Andreas Lorbach
Chinese Academy of Science
University of Konstanz
[email protected]
[email protected]
Shih-Yuan Liu
Boston College
[email protected]
Guy Lloyd-Jones
University of Edinburgh
[email protected]
Lauren Longobardi
[email protected]
Ryan Robert Maar
[email protected]
Donal Macartney
Queen's University
[email protected]
Benjamin Macphail
McMaster University
[email protected]
Ross Mancini
[email protected]
Sanjay Manhas
[email protected]
Todd Marder
[email protected]
Brian Mariampillai
Green Center Canada
[email protected]
Caleb Martin
Baylor University
[email protected]
Jerry Martin
Systems for Research
Washington State University
[email protected]
Donald S. Matteson
Sean McDonald
Queen's University
[email protected]
John McGough
[email protected]
Michael Meier
[email protected]
Jennifer Melanson
Queen's University
[email protected]
Rebecca Melen
Cardiff University
[email protected]
Soren K. Mellerup
Queen's University
[email protected]
Reid E. Messersmith
Johns Hopkins University
[email protected]
Bijan Mondal
[email protected]
Matthew Morgan
[email protected]
Mehdi Mostajeran
[email protected]
Jens Mueller
University of Saskatchwan
[email protected]
Masaharu Nakamura
Kyoto University
[email protected]
Samantha Novoa
[email protected]
Marco Nutz
[email protected]
Martin Oestreich
Technische Universität Berlin
[email protected]
Sang OoK Kang
Korea University
[email protected]
[email protected]
[email protected]
131
Frank Pammer
Universität Ulm
[email protected]
Jun Pang
Northernchem Inc
[email protected]
Evan Patrick
[email protected]
Jian Pei
Peking University
[email protected]
Cheryl L. Peck
Virginia Tech
[email protected]
Warren Piers
[email protected]
Sarah Piotrkowski
Queen's University
[email protected]
Zaozao Qiu
Shanghai Institute of Organic Chemistry
[email protected]
Lacey Reid
Queen's University
[email protected]
Stephen Ritter
C&N News
[email protected]
Etienne Rochette
Laval University
[email protected]
Pjotr Roest
[email protected]
Jason Rygus
Queen's University
[email protected]
Liban M. A. Saleh
[email protected]
Webster Santos
Virginia Tech
[email protected]
David Schubert
US BORAX Inc.
[email protected]
Julia J. Segura-Uribe
[email protected]
Hiroyuki Shimogawa
Kyoto University
[email protected]
Ekaterina Slavko
[email protected]
Russell Snead
Virginia Tech
[email protected]
Victor Snieckus
Queen's University
[email protected]
John A. Soderquist
University of Puerto Rico
[email protected]
Datong Song
[email protected]
Alexander M. Spokoyny
Doug Stephan
[email protected]
Alain C. Tagne Kuate
Rutgers University
[email protected]
Kashif Tanveer
[email protected]
Mark S. Taylor
[email protected]
Pakkirisamy Thilagar
Indian Institute of Science (IISc)
[email protected]
Ching-Hua Tsai
Kaohsiung Medical University
[email protected]
Krishnan Venkatasubbaiah
National Institute of Science Education and Research
[email protected]
Matthias Wagner
Goethe-University Frankfurt
[email protected]
Atsushi Wakamiya
Kyoto University
[email protected]
Grace Wang
[email protected]
Lyuming Wang
Nagoya University
[email protected]
Suning Wang
Queen's University
[email protected]
Xiang Wang
Queen's University
[email protected]
Andrew Warner
[email protected]
Andrew Weller
University of Oxford
[email protected]
Steve Westcott
Lewis Wilkins
Mount Allison University
Cardiff University
[email protected]
[email protected]
Lena Winner
[email protected]
Zuowei Xie
The Chinese University of Hong Kong
[email protected]
Shigehiro Yamaguchi
Nagoya University
[email protected]
John Yamamato
Vertellus Specialties Inc
[email protected]
Dengtao Yang
Queen's University
[email protected]
Kang Yuan
Queen's University
[email protected]
K. Yuvaraj
[email protected]
Matthew Zamora
Nanalysis Corp
[email protected]
Fangdong Zhuang
Peking University
[email protected]
132
[email protected]
Notes
133

Boron in the Americas

Transcription

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