Catalytic Synthesis of a Methylmalonate Salt from Ethylene and Carbon Dioxide through Photoinduced Activation and Photoredox-Catalyzed Reduction of Nickelalactones

Catalytic 1,1-dicarboxylation of ethylene with CO2 to form a methylmalonate salt was achieved by a Ni/Ir dual-catalyst system under photoirradiation conditions. In this reaction, photoenergy was utilized not only for the reduction of the methylmalonate Ni(II) complex but also for the transformation of the nickelalactone to the methylmalonate complex. By careful mechanistic investigations, it was revealed that photoirradiation promotes not only isomerization of five-membered to four-membered nickelalactones but also insertion of the second molecule of CO2 to form methylmalonate complexes via triplet excited states of the four-membered nickelalactones. This is an unprecedented example of catalytic methylmalonate synthesis from ethylene and CO2.