Approach for 2-(arylthio)imidazoles and imidazo[2,1-]thiazoles from imidazo[2,1-][1,3,4]thiadiazoles by ring-opening and -reconstruction

A highly efficient one-pot synthesis of imidazo[2,1- b ]thiazole derivatives has been developed and proceeds via a ring-opening and ring-closing reconstruction of imidazo[2,1- b ][1,3,4]thiadiazoles with phenylacetylene in the presence of potassium tert -butoxide ( t -BuOK) under very mild reaction conditions. A proposed mechanism is calculated computationally using a DFT method at the B3LYP/6-31+G(d,p) level. The imidazo[2,1- b ][1,3,4]thiadiazoles are also successfully converted to a series of 2-(arylthio)-1 H -imidazoles using aryl halide as a reactant and copper( ii ) acetylacetonate (Cu(acac) 2 ) as a catalyst under microwave irradiation conditions. The key features of these reactions are the use of readily available reagents, simple operation, the convenient utilization of new heterocyclic synthons, and a great variety of substrates with functional group compatibility. Useful heterocyclic synthons of imidazo[2,1- b ][1,3,4]thiadiazoles were developed to synthesize imidazo[2,1- b ]thiazoles and 2-(arylthio)-1 H -imidazoles under mild reaction conditions.