Fourth-Generation Oxidative Cross-Coupling Reactions

Over the past several years, a fourth-generation oxidative cross-coupling strategy has been developed, which can construct C-C and C-X (X = heteroatom) bonds directly under external oxidant-free conditions and release hydrogen gas as the sole side product. Because of the thermodynamics difficulty of the loss of H2 in this reaction, input of external energy is required to provide a thermodynamic driving force. Based on the source of external energy in the cross-coupling reactions, the fourth-generation oxidative coupling reactions can be divided mainly into three types in this text, including thermal energy-driven cross-coupling reactions, visible-light-mediated cross-coupling reactions, and electrochemical dehydrogenative reactions.