An improved procedure for the preparation of 3-carbometfaoxy-4-oxotetrahydrothiopyran, 2- and 4-carbomethoxy-3-oxotetrahydrothiophene

Abstract

An improved procedure for the preparation of the title compounds 1-3 has been developed. Direct condensation of methyl 3-mercaptopropionate with methyl acrylate using sodium hydride as a base gave compound 1 in good yield. The reaction of methyl thioglycolate and methyl acrylate at 0 °C gave compound 2 as the major product whereas at lower temperature (−40 °C) isomer 3 was found as the major product. The condensation reactions of methyl thioglycolate with methyl methacrylate and crotonate were also carried out.