Recent advances in chelation-assisted site- and stereoselective alkenyl C-H functionalization.

Olefinic C-H functionalization represents an atom- and step economic approach to valuable olefin derivatives from simpler ones, but controlling the selectivity remains a challenge. Remarkable progress has been made in the site-selective C-H functionalization of arenes and alkanes, but there are still limited examples of selective C-H functionalization of olefins presumably due to the lability and easy decomposition of the alkenyl moiety. Chelation-assisted C-H activation represents an efficient protocol for site- and stereo-selective construction of carbon-carbon and carbon-heteroatom bonds. This review highlights recent advances in vicinal- and geminal-group-directed olefinic C-H functionalization, including alkenylation, arylation, alkynylation, alkylation, halogenation, silylation, cyanation and annulation by the formation of exo-/endo-metallocycles. In particular, geminal-group-directed C-H functionalization is covered for the first time, as well as distal-selective alkenyl C-H functionalization under palladium/norbornene cooperative catalysis, which provides novel disconnections in retrosynthetic analysis and represents the future trend in green chemistry.