Unveiling the Potential of Sulfenic Acid Anions: Reactions, Synthesis and Computation
Adrian
Schwan
Department
of
Chemistry
University
of
Guelph
Wednesday,
November
13,
2019
2:30
p.m.
Main
Link
Room
(EIT-2053/MacN-101)
Coffee
and
treats
will
be
served.
All
are
welcome
to
attend
this
weekly
seminar
series.
Abstract:
Sulfenic
acid
anions
(RSO-M+)1
represent
a
means
of
introducing
nucleophilic
sulfur
entities
already
possessing
a
single
oxygen.
These
species
are
prochiral
and
their
alkylation
chemistry
results
in
the
direct
formation
of
a
sulfoxide
while
providing
possibilities
for
stereoselectivity,
since
the
sulfoxide
is
a
stereogenic
centre.
The
Schwan
group
has
demonstrated
a
number
of
diastereoselective
alkylation
reactions
and
has
suggested
various
internal
coordination
structures
involving
the
sulfenate
counterion
to
account
for
the
observed
stereoselectivity.2,3
We have achieved diastereoselective alkylation chemistry, using both sulfenates and electrophiles which hold internal carbon chirality. In one case, the products have been further elaborated to provide a preparation of isomeric dialkyl pyrrolidines, known constituents of ant venom.4
We have also established that benzylation of a protected cysteinesulfenate occurs with dr’s ranging from 89:11 to 95:5.2 Recently, we have initiated model computational studies to assist in determining the origins of the diastereoselection. Our findings identify the relative importance of lithium counterion coordination and sulfenate oxygen hydrogen bonding.5 We have also modelled substrates that possess an asymmetric b-(protected)amino group with varied protection groups.
The talk will outline some fundamentals of sulfenate chemistry, our contributions to diastereoselective alkylations, the preparation of the pyrrolidine alkaloids and the computational work which identifies sulfenate structures that may be responsible for the stereochemical outcomes.
- O’Donnell, J. S.; Schwan, A. L. J. Sulfur Chem. 2004, 25, 183− 21
- Schwan, A. L.; Verdu, M. J.; Singh, S. P.; O’Donnell, J. S.; Ahmadi, A. N. J. Org. Chem. 2009, 74, 6851−6854.
- Soderman, S.C.; Schwan, A.L. J. Org. Chem. 2013, 78, 1638−1649.
- Soderman, S.C.; Schwan, A.L. Org. Lett. 2013, 15, 4434–4437
- Schwan, A.L. Eur. J. Org. Chem. 2019, 519–526.
Upcoming (GWC)2 Wednesday Afternoon Research Seminars – Fall 2019
Date | Speaker | Title |
20 November |
France-Isabelle
Auzanneau University of Guelph | Mapping the Epitopes of Anti-polymeric Lewis X Monoclonal Antibodies with Synthesis and Immunochemistry |
27 November |
Subha
Kalyaanamoorthy University of Waterloo | Applications of Computational Modeling in Chemical Biology |