Site-Selective Alkenylation of δ-C(sp3)-H Bonds with Alkynes via a Six-Membered Palladacycle

Most chelation-assisted aliphatic C-H activation proceeds through a kinetically favoted five membered cyclometalated intermediate. Here, we report the first site-selective alkenylation of delta-C(sp(3))-H in the presence of more accessible gamma-C(sp(3))-H bonds via a kinetically less favored six-membered palladacyde. A wide range of functional groups are tolerated, and the unique protocol can be applied to the synthesis of chiral piperidines. Moreover, mechanistic insights have been conducted to elucidate the origin of the unusual site selectivity.