Visible-light-driven external-photocatalyst-free alkylative carboxylation of alkenes with CO2

Herein, we report a novel protocol for visible-light-driven alkylative carboxylation of alkenes with CO 2 in the absence of external photocatalyst. Under the irradiation of visible light, a variety of 4-alkyl-1,4-dihydropyridines (alkyl-DHPs) serve as not only alkyl radical precursors but also photoexcited reductants probably with the potential to reduce benzyl radicals. Several styrenes and acrylates are applicable in this reaction to give structurally diverse carboxylic acids in good to excellent yields. These reactions feature mild reaction conditions (1 atm of CO 2 , room temperature, visible light, photocatalyst- and transition metal-free), good functional group tolerance, easy scalability, as well as high regio-, and chemo-selectivity. Mechanistic investigations provide evidence that alkyl radical, benzyl radical and carbanion might be involved in this reaction, providing a novel strategy for CO 2 utilization.