Copper(II)-catalyzed oxidation of 4-carboxythiazolines and 4-carboxyoxazolines to 4-carboxythiazoles and 4-carboxyoxazoles

A mild copper(II)-catalyzed oxidation of 4-carboxythiazolines and 4-carboxyoxazolines to 4-carboxythiazoles and 4-carboxyoxazoles has been developed. Various substrates with alkyl or aryl substitutions at 2-position on azoline ring could be smoothly oxidized to the desired products in good to excellent yields. Moreover, the hydrolysis of the ester group could be avoided under this method.