Reactions of β-ketoesters and nitriles with carbon disulphide : Tautomerism of dithioesters and thio-Claisen rearrangement of ketene mercaptals

Abstract

By use of the ion pair extraction technique tetrabutylammonium salts of ethyl and methyl acetoacetate, ethyl benzoylacetate, and cyanoacetone were reacted with CS 2 to give salts of dithioacids. Alkylation gave dithio-esters and ketene mercaptals. Rearrangements of allyl and crotyl ketene mercaptals of ethyl and methyl acetoacetate and ethyl benzoylacetate were studied. In the rearrangement of the dicrotyl ketene mercaptal of methyl acetoacetate an intermediate was detected supporting a four-step thio-Claisen rearrangement mechanism for dicrotyl ketene mercaptals, giving α-crotyl dithioesters with retention of the crotyl group.