Sparey, Tim (1995) Asymmetric synthesis using sulfimides. PhD thesis, University of Warwick.

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Abstract

Asymmetric synthesis, the synthesis of chiral molecules,
has developed into
one of the most important
areas of chemistry.
Numerous
methods are used to
prepare chiral compounds, one of which
involves
using chiral acyl anion
equivalents. The potential of
imides
of cyclic sulfimides
148
as chiral acyl
anion equivalents was
found to be limited to simple alkylations using sodium
hydride
and an alkyl
iodide in DMF. Alkylated adducts 154,158
and 159
were prepared with good
diastereoselectivity,
with the anti and anti-anti
geometries
being
preferred
for 154 and 158, and 159, respectively. The
conformations of the parent sulfimides 148 were investigated. We found that
cyclic sulfimides
(1,3,4-oxathiazines) 132 were inaccessible, which precluded
our investigation into the potential of this new class of compound as chiral
acyl anion equivalents. In the course of this work, the BPTM
group was
developed
as a replacement
for the troublesome PTM group as a protecting
group
for
primary, secondary and
benzylic
alcohols.
Vinyl
sulfimides
186
were prepared using a modified
Wadsworth-Emmons
reaction, with good
E
selectivity.
Additions
of alcohols
to give adducts
185
proceeded with good
diastereoselectivity. The
attempted
deprotection
of
adduct
185b
using
hydrogenolysis
resulted
in
reduction of the
sulfimide
group to yield protected
ß-hydroxy
sulfide
192. Radical additions to
vinyl
sulfimides
186
resulted
in 2-vinyl
oxa-heterocycles
202
and
210,
with
THE
and
THP
as solvent, respectively.
A
radical addition mechanism
has been
proposed,
but
uncertainty still exists as this mechanism can not explain
both
triethylborane
and
benzoyl
peroxide mediated reactions as the E/Z
selectivities are
different. At this
stage, an
ionic
mechanism can not
be
ruled
out.
2-Vinyl
oxa-heterocycles 202
and
210 have been
converted, using
Taylor's
variant of the Malherbe-Bellus
reaction,
into 9-
and
10-membered
lactones 220 and
221,
respectively, which are closely related to a number of
important natural products.
Considerable progress
has been
made
in developing a new asymmetric
sulfimidation procedure.
Promising
enantioselectivites
have been
observed
using a copper-catalysed
decompsition
of tosyl azide or
PhI=NTs 224 into
nitrenes.
Interception
of the nitrenes
by
sulfide within the chiral influence
of
C-2
symmetric chiral
ligands 225 or 231 yielded sulfimide 65. A discrete
copper-nitrene species is thought to be an intermediate in the catalytic cycle.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Asymmetry (Chemistry), Asymmetric synthesis, Organic compounds -- Synthesis
Official Date:	September 1995
Dates:	Date Event September 1995 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Taylor, Paul C. (Paul Christopher)
Extent:	1 volume (various leaves) : illustrations
Language:	eng

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