Synthesis of Ketene Thioacetals and Their Monosulfoxide Derivatives and the Thermal Rearrangements of Diallylic Ketene Thioacetals

Abstract

Ketene dimethyl thioacetal monosulfoxide was prepared in 68% overall yield in two steps starting from methylmagnesium chloride. The yield of dithioacetic acid was improved significantly by employing tetrahydrofuran as solvent and using elevated temperatures. A one-pot synthesis of ketene thioacetals from alkyl halides was developed and several ketene thioacetals were prepared by this method. Direct oxidation of ketene thioacetals using m-chloroperoxybenzoic acid provided a general route to ketene thioacetal monosulfoxides. In cases where E and Z isomeric ketene thioacetal monosulfoxides were possible, the E/Z isomeric ratio increased as the substituents on the ketene double bond was increased in size