Nickel-Catalyzed Alkynylation of a C(sp2)-H Bond Directed by an 8-Aminoquinoline Moiety

An efficient nickel catalyst system for the direct ortho C-H alkynylation of the amides has been successfully developed with the directing assistance of 8-aminoquinoline. It was found that the flexible bis(2-dimethylaminoethyl) ether (BDMAE) ligand was critical to achieve the optimized reactivity. This protocol showed good tolerance toward not only a wide range of (hetero)aryl amides but also the rarely studied alpha,beta-unsaturated alkenyl amide. The directing amide group could be easily transformed to aldehyde or ester in high yields. Meanwhile, the removable TIPS substituent on the resultant aryl/alkenyl alkynes could be further converted to an aryl moiety through a Sila-Sonogashira coupling reaction. This Ni-catalyzed alkynylation procedure provides an alternative approach to construct a C(sp(2))-C(sp) bond.