Al. Schwan et al., ON THE CONFORMATIONAL PREFERENCES OF THE DEHYDROCHLORINATION OF ALPHA-CHLOROSULFOXIDES, Canadian journal of chemistry, 72(2), 1994, pp. 312-324
Several acyclic alpha-chlorosulfoxides have been shown to undergo a ga
mma-dehydrochlorination upon treatment with LDA. The proposed immediat
e products of gamma-dehydrochlorination, thiirane-S-oxides, are unstab
le under the basic conditions and react further with the LDA; the isol
ated products are usually E-alkenes and (or) E-vinyl sulfoxides. Some
of the proposed intermediate thiirane-S-oxides, compounds 6, 7, 8, and
18, were synthesized independently and treated with one equivalent of
LDA in order to mimic the second step of the overall dehydrochlorinat
ion/ring opening sequence. The products obtained from the reactions of
compounds 6 and 18 compared favourably with those products which were
believed to arise from certain conformations of alpha-chlorosulfoxide
s 1kB and 1e, respectively. The addition of one equivalent of LDA to 1
kA afforded a mixture containing thiirane-S-oxide 8, which is proposed
as the immediate product of gamma-dehydrochlorination of 1kA. The con
figurations of 1kB and 1hA were both shown to be threo by X-ray crysta
llographic studies. Those conformations which are preferred for the de
hydrochlorination possess a geometry where the sulfinyl oxygen is anti
to any of the substituents of the ring carbons.