Straightforward Approach to 5-Substituted 7H-Imidazo[2,1-b] [1,3]thiazines via Cyclization of 2-Alkynylthioimidazoles

Abstract

AbstractElectrophile-initiated nucleophilic cyclization of 2-alkynylthiobenzimidazoles is a useful tool for synthesizing new heterocyclic systems. However, halogen-initiated cyclization demonstrates poor selectivity between electrophilic addition and substitution reactions using other imidazole analogues. In this research, several different coinage metal catalysts were employed to broaden the scope of 7H-imidazo[2,1-b][1,3]thiazines in atom-economic manner. Selective 6-endo-dig pathway reactions were achieved in good to excellent yields using various 2-alkynylthioimidazoles with AuCl as the catalyst in DCE/DCM.