Nickel(II)-Catalyzed Direct Arylation of C-H Bonds in Aromatic Amides Containing an 8-Aminoquinoline Moiety as a Directing Group

Arylation via the cleavage of the ortho CH bonds by a nickel-catalyzed reaction of aromatic amides containing an 8-aminoquinoline moiety with aryl iodides is reported. The reaction shows a high functional group compatibility. The reaction proceeds in a highly selective manner at the less hindered CH bonds in the reaction of meta-substituted aromatic amides, irrespective of the electronic nature of the substituents. Electron-withdrawing groups on the aromatic amides facilitate the reaction. Various mechanistic experiments, such as deuterium labeling experiments, Hammett studies, competition experiments, and radical trap experiments, have been made for better understanding the reaction mechanism. It is found that the cleavage of CH bonds is reversible on the basis of the deuterium labeling experiments. Both Ni(II) and Ni(0) show a high catalytic activity, but the results of mechanistic experiments suggest that a Ni(0)/Ni(II) catalytic cycle is not involved.