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. Transformations in organic chemistry are mainly limited to the incorporation of only one equivalent of the greenhouse gas CO2 per substrate. Now, a visible-light photoredox-catalysed dicarboxylation of alkenes, allenes and arenes allows the incorporation of two CO2 molecules into organic compounds.