Copper-Catalyzed Carboxylation of Aryl Thianthrenium Salts with CO 2 .

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.