Regioselective, Solvent- and Metal-Free Chalcogenation of Imidazo[1,2-a]pyridines by Employing I2 /DMSO as the Catalytic Oxidation System

Abstract

Highly efficient molecular-iodine-catalyzed chalcogenations (S and Se) of imidazo[1,2-a]pyridines were achieved by using diorganoyl dichalcogenides under solvent-free conditions. This approach afforded the desired products that had been chalcogenated regioselectively at the C3 position in up to 96 % yield by using DMSO as an oxidant, in the absence of a metal catalyst, and under an inert atmosphere. This mild, green approach allowed the preparation of different types of chalcogenated imidazo[1,2-a]pyridines with structural diversity. Furthermore, the current protocol was also extended to other N-heterocyclic cores.

Keywords: green chemistry; iodine; nitrogen heterocycles; selenium; sulfur.