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.