Miljanic Group Meeting Literature

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Ognjen . Miljanic
Miljanic Group Meeting / Literature University of
Houston ? Houston, TX ? January 2nd 2009
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Three Papers from 2007 and 2008
Diversity through Isosterism The Case of
Boron-Substituted 1,2-Dihydro-1,2-azaborines Adam,
J. V. Marwitz, Eric R. Abbey, Jesse T. Jenkins,
Lev N. Zakharov, Shih-Yuan Liu Org. Lett. 2007,
9, 49054908.
Crystal Clear Structural Evidence for Electron
Delocalization in 1,2-Dihydro-1,2-azaborines Eric
R. Abbey, Lev N. Zakharov, Shih-Yuan Liu J. Am.
Chem. Soc. 2008, 130, 72507252.
A Hybrid Organic/Inorganic Benzene Adam, J. V.
Marwitz, Myrna H. Matus, Lev N. Zakharov, David
A. Dixon, Shih-Yuan Liu Angew. Chem. Int. Ed.
2008, 47, ASAP.
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Collaborative Research
Shih-Yuan Liu PostdocMassachusetts Institute of
Technology (200306, Daniel G. Nocera) PhDMassach
usetts Institute of Technology (2003, Gregory C.
Fu) DiplomaVienna University of Technology
(1997) Professor at University of Oregon since
2006.
Lev N. Zakharov Staff crystallographer at the
University of Oregon (since 2004).
David A. Dixon PhDHarvard University
(1976) BSCalifornia Institute of Technology
(1971) Professor at University of Alabama.
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Oregon is Green and Pretty!
? Oregon is the 9th biggest US state by area (2.5
times smaller than TX) ? Oregon ranks as 27th US
state by population (3.7 million, 7 times smaller
than TX) ? Capital city is Salem, biggest city is
Portland (600,000) ? Moderate climate pleasant
summers and rainy (but not overly cold) winters ?
Two big universities University of Oregon
(Eugene) and Oregon State (Corvallis) ? Well
known for beer, wine, agriculture, and tourism
(skiing, hiking, camping)
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Boron-Containing Heterocycles are Important
? Theoretically relevant in studies of
aromaticity Chiavarino, B. et. al. J. Am. Chem.
Soc. 1999, 121, 1120411210. ? BN bond is
isoelectronic and isosteric with CC, important
for pharmaceuticals Morin, C. Tetrahedron 1994,
50, 1252112569. ? Boron neutron-capture therapy
(BNCT) for cancer Barth, R. F. et. al. Clin.
Cancer Res. 2005, 11, 39874002. ? Borazine is a
precursor to BN ceramics Mokhtari, M. et al.
Chem. Eur. J. 1996, 2, 12691274. ? Borazine is a
side-product in the use of ammonia-borane in
hydrogen storage Marder, T. B. Angew. Chem. Int.
Ed. 2007, 46, 81168118.
Faraday, M. Philos. Trans. R. Soc. London 1825,
115, 440466. Stock, A. Pohland, E. Ber. Dtsch.
Chem. Ges. 1926, 59, 22102215.
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Alkene Metathesis is the Key Synthetic Step
Marwitz, A. J. V. Abbey, E. R. Jenkins, J. T.
Zakharov, L. N. Liu, S.-Y. Org. Lett. 2007, 9,
49054908.
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BCl Bond Can be Nucleophilically Substituted
Marwitz, A. J. V. Abbey, E. R. Jenkins, J. T.
Zakharov, L. N. Liu, S.-Y. Org. Lett. 2007, 9,
49054908.
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Are 1,2-Azaborines Aromatic?
To determine this, the authors performed direct
structural comparison with
in order to evaluate the delocalization in the
fully unsaturated structure
This study is analogous to the comparison of
benzene with cyclohexadiene!
Abbey, E. R. Zakharov, L. N. Liu, S.-Y. J. Am.
Chem. Soc. 2008, 130, 72507252.
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Model Compounds Were Synthesized Divergently
Abbey, E. R. Zakharov, L. N. Liu, S.-Y. J. Am.
Chem. Soc. 2008, 130, 72507252.
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Azaborine is Clearly Planar
Abbey, E. R. Zakharov, L. N. Liu, S.-Y. J. Am.
Chem. Soc. 2008, 130, 72507252.
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Delocalization Supports Aromaticity
Bond
Length (Å)
NB
1.403
1.405
1.407
1.417
1.446
1.584
1.590
1.559
1.579
1.518
BC4
1.493
1.338
1.504
1.363
1.511
C4C3
1.319
1.479
1.494
1.412
C3C2
1.511
1.508
1.493
1.503
1.319
1.356
C2C1
1.479
1.477
1.479
1.432
1.383
C1N
? In compounds AD, bond between N and C is a
double bond (1.41 Å) ? Formal double bonds in
BD lengthen upon aromatization ? All formal
single bonds shorten upon aromatization
Abbey, E. R. Zakharov, L. N. Liu, S.-Y. J. Am.
Chem. Soc. 2008, 130, 72507252.
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Finally, the Unsubstituted Azaborine!
Marwitz, A. J. V. Matus, M. H. Zakharov, L. N.
Dixon, D. A. Liu, S.-Y. Angew. Chem. Int. Ed.
2008, 47, ASAP.
13
NMR Studies Confirm Aromaticity
? Boron S 3/2 1111 quartet ? Nitrogen S
1 111 triplet
Marwitz, A. J. V. Matus, M. H. Zakharov, L. N.
Dixon, D. A. Liu, S.-Y. Angew. Chem. Int. Ed.
2008, 47, ASAP.
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NH Bond is Protic, BH Bond is Not Hydridic
Marwitz, A. J. V. Matus, M. H. Zakharov, L. N.
Dixon, D. A. Liu, S.-Y. Angew. Chem. Int. Ed.
2008, 47, ASAP.
? The study nicely illustrates the thought
process 1) simple synthetic development 2)
fundamental structural studies 3) the holy
grail discovery ? Versatility in B-substitution
in boron heterocycles, especially in
azaborines ? Robustness of alkene metathesis
protocols ? Use of Cr(CO)3 as a protecting group
for the aromatic nuclei
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Notes on Preparing Effective Slides
? Design be consistent, but rational ? You are
presenting! Make sure the audience notices both
you and the research Avoid using laser pointer
too muchit takes the focus away from you ?
Slide Titles should be messages, not description
of what you did Compound A is Synthesized in 8
Steps is an informative title Synthetic Route
towards Compound A is not ? Use contrast to
highlight differences in importance Human brain
does not give any inherent meaning to color
(except RED) ? Maximize data-to-ink ratio by
minimizing slide junk Avoid bold arrows,
borders, vignettesthey use space and convey
nothing! ? Give credit where credit is due,
preferably with pictures of people Small
personal details make presentation engaging (but
maintain balance) ? Do not thank your
audience If your presentation was any good, they
should be thanking you