A novel approach to 1,4-oxathiocines: the thermal rearrangement of thiophenium methylides

Abstract

2,5-Disubstituted thiophenes react at ambient temperature under rhodium acetate catalysis with various diazoketones to give thiophenium methylides which rearrange thermally to give 1,4-oxathiocines, as confirmed by an X-ray crystal structure determination; one of these, 3-ethoxycarbonyl-5,8-dichloro-2-methyl-1,4-oxathiocine, corrects a supposed cyclopropathiophene structure and further rearranges to give ethyl 2,4-dichloro-5-hydroxy-6-methylbenzoate.