I2/DMSO-enabled cascade Michael addition/oxidative cyclization: access to imidazo[2,1-b][1,3,4]thiadiazoles

Abstract

A straightforward protocol for accessing imidazo[2,1-b][1,3,4]thiadiazoles via I₂-catalyzed tandem Michael addition–oxidative cyclization has been developed. A one-pot approach to access imidazo[2,1-b][1,3,4]thiadiazoles from hydrazones, chalcones, and KSCN has been demonstrated. Both I₂ and DMSO are essential and the reaction proceeds through a radical pathway. The strategy is also extendable to the synthesis of imidazo[1,2-a]pyridine and benzo[d]imidazo[2,1-b]thiazole derivatives. Wide functional group tolerance, the use of simple and unfunctionalized building blocks and inexpensive catalysts, large scalability, and easy execution are the notable features of this approach.