Functionalization of Olefinic C-H Bonds by an Aryl-to-Vinyl 1,4-Nickel Migration/Reductive Coupling Sequence.

An attractive approach to selective functionalization of remote C-H bonds is a metal/hydride shift/cross-coupling reaction sequence. Complimentary to the heavily exploited 1,2-nickel/hydride shift along an sp 3 chain, a chain-walking process, the 1,4-nickel/hydride shift along an sp 2 chain is more complex. Here we report an unprecedented aryl-to-vinyl 1,4-nickel/hydride shift reaction, in which the migratory alkenylnickel species generated in situ is selectively trapped by one of various coupling partners, such as isocyanates, alkyl bromides, aryl chlorides or alkynyl bromides, allowing regio- and stereoselective access to trisubstituted alkenes. In contrast to the well-reported ipso-aryl coupling reactions, this strategy provides remote alkenyl C-H functionalized products with good yield and with excellent chemo-, regio- and E/Z-selectivity.