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

Catalytic 1,1-dicarboxylation of ethylene with CO2to 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 themethylmalonate Ni(II) complex but also for the transformation ofthe nickelalactone to the methylmalonate complex. By carefulmechanistic investigations, it was revealed that photoirradiationpromotes not only isomerization offive-membered to four-membered nickelalactones but also insertion of the secondmolecule of CO2to form methylmalonate complexes via tripletexcited states of the four-membered nickelalactones. This is anunprecedented example of catalytic methylmalonate synthesis fromethylene and CO2.