Cobalt-catalyzed hydroarylation of alkynes through chelation-assisted C-H bond activation

Ternary catalytic systems consisting of cobalt salts, phosphine ligands, and Grignard reagents promote addition of arylpyridines and imines to unactivated internal alkynes with high regio- and stereoselectivities. Deuterium-labeling experiments suggest that the reaction involves chelation-assisted oxidative addition of the aryl C−H bond to the cobalt center and insertion of the C−C triple bond into the Co−H bond, followed by reductive elimination of the resulting diorganocobalt species.