Synthesis of 4-methylene-4H-benzo[d][1,3]thiazines via a tandem reaction of 1-(2-alkynylphenyl)ketoximes with Lawesson's reagent

Abstract

1-(2-Alkynylphenyl)ketoximes react with Lawesson's reagent catalyzed by InCl(3) and cyanuric chloride leading to 4-methylene-4H-benzo[d][1,3]thiazines in good yields. This tandem reaction proceeds with high efficiency through Beckmann rearrangement, thioamide formation, and intramolecular nucleophilic cyclization.