The preparation of derivatives containing the imidazo[2,1-b]thiazine and 1,2,4-triazolo[3,2-b][1,3]thiazine systems

Abstract

The cyclisation of 3-mercapto-1,2,4-triazole (1a) and 2-mercaptoimidazole (7) with diethyl ethoxymethylenemalonate is shown to produce 6-ethoxycarbonyl[1,2,4]triazolo[3,2-b][1, 3]thiazin-5-one (2a) and 6-ethoxycarbonylimidazolo[2,1-b][1,3]thiazin-5-one (8a) respectively. A minor product associated with the formation of compound (2a) was identified as [1,2,4]triazolo[3,2-b][1,3]thiazin-5-one (2b) by X-ray analysis. The ¹³C n.m.r. data for these compounds were useful in correlating their structures.