Transition-Metal-Catalyzed, Chelation-Assisted C-H Alkenylation and Allylation of Organic Molecules with Unactivated Alkenes

Olefins are important building blocks and are widely utilized in synthetic organic chemistry. Owing to its omnipresence and unique reactivity, the functionalization of alkenes has become a powerful method for constructing complex organic molecules. In this context, direct chelation-assisted C-H olefination at the inert C-H bonds represents the most straightforward synthetic method for introducing the alkenyl group into organic compounds in a highly regio- and stereoselective manner. Despite the remarkable advances in chelation-assisted C-H olefination reaction, most of the successful transformations are restricted to activated or electronically biased olefins such as acrylates, styrenes, acrylamides, vinyl sulfones, and vinyl phosphonates. Literature reports on chelation-assisted C-H olefination with unactivated or electronically unbiased alkenes are limited due to poor intrinsic reactivity and regioselectivity issues. Despite significant challenges, the past few years have witnessed tremendous growth. The present review describes the recent advances in the chelation-assisted C-H olefination and allylation of aromatics, alkenes, and heteroaromatics with unactivated alkenes via the concerted-metallation- deprotonation pathway.Transition metals such as palladium, rhodium, iridium and cobalt are widely used for these kind of transformations. The scope, mechanistic investigation, and limitation of the alkenylation and allylation reactions are discussed elaborately. The present review includes all the reported C-H olefination and allylation reactions with unactivated olefins via the base-assisted deprotonation pathway.