Copper‐Catalyzed Carboxylation of Aryl Thianthrenium Salts with CO2

Abstract Carboxyl group is one of the most widely used groups in organic synthesis. Herein, an efficient copper‐catalyzed carboxylation of aryl thianthrenium salts with carbon dioxide (CO 2 ) at room temperature has been developed. The reaction employs low loading of cuprous chloride catalyst under 1 atm CO 2 and exhibits good functional group tolerance. In combination with C−H thianthrenation of aromatic hydrocarbons, this work provides an efficient method for the site‐selective C−H carboxylation of aromatic hydrocarbons. It may serve as a significant late‐stage carboxylation tool for the modification of drug molecules in the future.