Carboxylation of Heteroarenes with Carbon Dioxide under Polysulfide Anion Photocatalysis.

Herein, we report the carboxylation of heteroarenes such as thiophenes, furans, benzothiophenes, benzofurans, and thiazoles with atmospheric carbon dioxide (CO2) in the presence of catalytic potassium polysulfide (K2Sx) in aqueous dimethyl sulfoxide (DMSO) under irradiation with visible light. The process demonstrates redox-neutral carboxylation of a heteroaromatic C-H bond in a regioselective manner. Mechanistically, the reaction is likely initiated by the generation of heteroarene radical anions through single-electron reduction of heteroarenes, followed by carboxylation and oxidative rearomatization to liberate heteroarene carboxylic acids.