Cu(I)/<i>N,N</i>-Imine Ligand Catalyzed C(sp³)–C(sp) Coupling of Alkyl Bromides with Alkynes: Scope and Mechanistic Investigation

We have developed an efficient Cu/N,N-bidentate imine ligand catalytic system for C(sp3)–C(sp) coupling to obtain internal alkynes, di/trisubstituted allenes and strained bridged cyclic lactams in moderate to excellent yields from readily available alkyl(benzyl) bromides in one-pot transformation. Density Functional Theory (DFT) assisted mechanistic study along with control experiments support the involvement of bialkynylated copper species which undergo single electron transfer (SET) with alkyl halides to generate radical intermediate in the reaction. The N,N-bidentate imine ligand plays a vital role in stabilization of intermediate copper complex and facilitates the product formation