Microwave-assisted hydrogen peroxide-mediated synthesis of benzoxazoles and related heterocycles via cyclodesulfurization
A novel approach has been developed to construct benzoxazoles and similar N- and S-containing heterocycles from their corresponding isothiocyanates and o-substituted anilines via cyclodesulfurization. The reaction was found to proceed via in situ formation of disubstituted thiourea, followed by intramolecular cyclodesulfurization to yield the desired benzazole. Cyclodesulfurization was achieved by the application of safer and inexpensive oxidant, hydrogen peroxide (H2O2) under microwave irradiation. In addition to the safe environmental footprints that hydrogen peroxide exhibits, the absence of any base or additive makes it a mild and green synthetic strategy. This method contributes to the field of metal- and base-free cyclodesulfurization, thereby aids the synthesis of pharmacologically potent heterocyclic scaffolds.
