Unexpected formation of pyrrolo[2,1-b]thiazoles by rearrangement of alpha-hydroxydihydro-1,4-thiazines

Abstract

A new synthesis of pyrrolo[2,1-b]thiazoles (5) is described. Hydrolysis of acetoxy djhydro-1,4-thiazine (2) prepared by Pummerer reaction of dihydro-1,4-thiazine sulfoxide gave the intermediate alpha-hydroxy sulfide (4). Dehydration of 4 gave pyrrolo[2,1-b]thiazoles (5). The reaction mechanism for the formation of 5 including the intermediate thiol (6) is discussed.