Mn(III)-based reactions of alkenes and alkynes with thiols. An approach toward substituted 2,3-dihydro-1,4-oxathiins and simple route to (E)-vinyl sulfides

Abstract The first example using manganese(III) acetate in the reaction of 1,1-diarylethenes with α-mercaptoketones was examined. A mixture of the ethenes and α-mercaptoketones was treated with manganese(III) acetate in acetic acid, affording cycloaddition products in moderate yields, together with substituted products. The reaction may involve the formation of a carbocation and subsequent cyclization to give the substituted 2,3-dihydro-1,4-oxathiin 3 . A similar reaction with thioglycolic acid gave 1,4-oxathiolan-2-one 7 . While thiyl radicals easily formed by manganese(III) oxidation with ethanethiol or benzenethiol reacted with alkynes to give preferentially ( E )-vinyl sulfides 10 in quantitative yields.