Direct C–H Carboxylation with Carbon Dioxide Using 1,2,3-Triazol-5-ylidene Copper(I) Complexes

1,2,3-Triazol-5-ylidene copper(I) complexes (tzNHC-Cu) efficiently catalyzed the direct C–H carboxylation of benzoxazole and benzothiazole derivatives with CO2 to give the corresponding esters in excellent yields after treatment with alkyl iodide. The tzNHC copper(I) complex, i.e., [(TPr)CuCl], worked somewhat more effectively than the corresponding imidazol-2-ylidene copper(I) complex [(IPr)CuCl] to give the carboxylation product in higher yields.