Dicarboxylation of alkenes, allenes and (hetero)arenes with CO2 via visible-light photoredox catalysis

Light-driven utilization of CO2 in organic synthesis is highly attractive because it mimics nature. However, such transformations are mainly limited to the incorporation of only a single CO2 molecule into organic compounds, far less than the number of CO2 molecules fixed in the product in photosynthesis. Here we report the visible-light photoredox-catalysed dicarboxylation of alkenes, allenes and (hetero)arenes with the incorporation of two CO2 molecules. This method realizes the formation of multiple C–C bonds with high chemo- and diastereoselectivities under mild conditions, which represents a simple, rapid and sustainable approach to valuable dicarboxylic acids. Moreover, this transition-metal-free protocol exhibits a low catalyst loading, good functional group tolerance, broad substrate scope, facile scalability and easy product derivatizations to give drug and material molecules. Mechanistic studies indicate a pathway by which a visible-light-induced two-electron reduction via sequential single electron transfer generates radical anions of such unsaturated substrates, broadening the repertoire of strategies.