A strategy for C-H activation of pyridines: Direct C-2 selective alkenylation of pyridines by Nickel/Lewis acid catalysis

The C-2 selective alkenylation of pyridine derivatives is achieved with a catalyst consisting of nickel and Lewis acid. Use of diorganozinc compounds as the Lewis acid catalyst gives C-2 monoalkenylation products, whereas AlMe₃ changes the reaction course to afford C-2 dienylated products, which are derived from double insertion of alkynes into the C(2)-H bond. The reaction demonstrates a broad substrate scope and proceeds with high chemo-, regio-, and stereoselectivities under mild conditions compared with previous examples of direct C-H functionalization of pyridines.