Metallaphotoredox catalysis for multicomponent coupling reactions

The combination of photoredox and transition metal catalysis, which is termed metallaphotoredox catalysis, is a powerful platform for building complex molecules under mild conditions. In particular, metallaphotoredox-catalyzed multicomponent coupling reactions, compared with traditional single transition metal-catalyzed reactions, do not require high temperature or moisture- and air-sensitive organometallic reagents and enable the rapid construction of value-added chemicals from easily available feedstocks. In recent years, a variety of metallaphotoredox-catalyzed multicomponent couplings have been developed to simultaneously construct C–C and C–X bonds under mild conditions and even to assemble chiral skeletons. These multicomponent reactions can be roughly divided according to their different radical receptors into alkene difunctionalizations, alkyne difunctionalizations, propellane difunctionalizations and so on. Although considerable progress has been achieved in this area, more efforts are still needed to meet the demands of modern green synthetic chemistry. In this review, we summarize the recent advances in the field of metallaphotoredox-catalyzed multicomponent coupling reactions and identify directions for future development.