Brønsted acid-catalyzed regioselective ring opening of 2H-azirines by 2-mercaptopyridines and related heterocycles; one pot access to imidazo[1,2-a]pyridines and imidazo[2,1-b]thiazoles

Abstract

A catalytic and versatile synthetic method for the synthesis of imidazo[1,2-a]pyridines has been developed. Brønsted acid-catalysis plays a major role in the regioselective ring opening of 2H-azirines. Nucleophilic attack via the N-centre of mercaptopyridines and their analogues, followed by cyclisation by cleaving the C–S bond, allowed a library of imidazo[1,2-a]pyridines and related heterocycles to be built. The reaction protocol has been applied to various 2H-azirines, 2-mercaptopyridines, and thiazole-2-thiols, illustrating the generality of reaction conditions. The practical applications include the synthesis of pharmaceuticals, such as anti-tumor agents. This study introduces a novel approach to the synthesis of functional molecules with extensive potential.