Visible-Light-Induced Arylcarboxylation of Activated Alkenes with Aryl Halides and Oxalate Enabled by Electron Donor–Acceptor Complex Formation

Simultaneous construction of two new C-C bonds in the alkene substrates regioselectively is significantly challenging. Herein, we report an unprecedented regioselective arylcarboxylation strategy of activated alkenes with readily available aryl halides and tetrabutylammonium oxalate as the reductant and C1 source under visible-light-induced conditions. The reaction proceeds smoothly to access various carboxylic acids in the absence of any catalysts, additives, metal promoters, or pre-established CO₂ atmosphere. The electron donor-acceptor (EDA) complex is formed between the stoichiometric amounts of tetrabutylammonium oxalate and aryl halides to trigger the single-electron reduction relay process after irradiation with visible light. The <i>in situ</i> generated oxalic radical anion species in the reaction undergoes homolysis of the C-C bond and releases the CO₂ radical anion and CO₂ as the potent reductant and C1 source, respectively, to facilitate the reductive carboxylation.