Recent advances in transition-metal-catalyzed functionalization of unstrained carbon-carbon bonds

Some recent advances in transition-metal complex catalyzed cleavage of unstrained carbon-carbon bonds, including C-C single bonds, C-C double bonds, and C-C triple bonds was reported. Many examples of unstrained C-C single bond cleavage catalyzed by various transition-metal complexes have been reported. Generally, functional groups adjacent to these bonds are necessary for these transformations. In the developed methods, oxidative addition, βcarbon elimination, decarbonylation, and retroallyation are common mechanisms for transition-metal complex catalyzed C-C single bond functionalization. Olefin metathesis and enyne metathesis reactions are very important methods for C=C double bond cleavage, and they have been well developed. Additionally, oxidative cleavage is another class of C=C bond activation process. Many transition-metal complexes have been developed for this kind of reaction using appropriate oxidants, especially molecular oxygen. Various mechanisms are proposed for cleavage of carbon-carbon bonds. The further development of new carbon-carbon bond cleavage reactions in this field will be expected to explore new catalytic systems with inexpensive transition-metal catalysts, under mild conditions, with green and sustainable oxidants, and with a wide substrate scope.