Thionation reactions of diacylketene thioacetals with the Lawesson reagent and analogues
Abstract
Attempted thionation of diacylketene thioacetals derived from dimedone with dithiadiphosphetane disulphides (the Lawesson reagent and analogues) led to the expected monothioacylketene thioacetals only when the thioacetal sulphur atoms formed part of a dithiolane or dithiane ring. Acyclic analogues readily underwent dealkylation and further reactions, giving a 1,2-dithiole-3-thione derivative as the main isolated product. Reaction of an acyclic ketene thioacetal with P4S10–Et3N in acetonitrile at –30 °C permitted the isolation of the primary dealkylation product, a dimedonedithiocarboxylate, in 44% yield. A phenoxaphosphorine derivative was isolated as a by-product in the synthesis of bis(phenoxyphenyl)dithiaphosphetane disulphide.