A Study of the Reactions Between Sulphur Halides and Oxyhalides with Compounds Containing Active Methylene Groups

Abstract

A series of reactions of thionyl chloride with compounds
containing active methylene groups has led to a new synthesis of
tetrasubstituted alkenes. The synthesis employs cheap and readily
available starting materials, and leads to good yields of alkenes in a
Simple one-stage process.

The study has been divided into two main parts, the first being an
investigation of the reaction of thionyl chloride with a number of
compounds containing carbon-hydrogen bonds labilised by the presence of
adjacent electron-withdrawing groups. Hence, some idea of the scope and
utility of the new synthesis has been obtained.

The second part of the study has been devoted to the determination
of a reaction mechanism or mechanisms. It is shown that a sulphinyl
chloride is formed by an ionic route and in most cases is unstable under
the reaction conditions. loss of hydrogen chloride from the sulphinyl
chloride leads to a sulphine which in turn yields an alkene via an
intermediate thiiran.

Not every reaction yields an alkene, however, and in certain cases
the intermediates postulated in the alkene synthesis are too stable to
react further with thionyl chloride. This results in a sulphinyl
chloride and two thiirans being isolated as major products.

An attempt has been made to explain the formation of di(acetylalkoxycarbonyl)
methyl sulphide from the reaction of acetoacetic esters
and thionyl chloride at room temperature, It is thought that a
different pathway is followed owing to the reaction of the thionyl
chloride with the Bole tautomer rather than with a carbanionic-type
species.

Both sulphuryl chloride and disulphur dichloride have been used to
prepare compounds by known routes. The products of these reactions are compared with those from certain thionyl chloride reactions in
order to verify particular structures.

Date of Award	1973
Original language	English