Highly Chemoselective Access to 2,2′-Diaminobiaryls via Ni-Catalyzed Protecting-Group-Free Coupling of 2‑Haloanilines

The development of strategies to access 2,2′-diaminobiaryl derivatives via a transition-metal-catalyzed coupling reaction from protecting-group-free starting materials is a challenging task to accomplish, owing to the easy occurrence of undesired side reactions. The exploitation of Ni-catalyzed direct homocoupling of unprotected 2-haloaniline analogues to produce 2,2′-diaminobiaryls with a readily available and inexpensive bipyridine ligand has been described. This approach was highlighted by its high chemoselectivity, broad substrate scope, and functional group compatibility. The mechanistic and calculation studies indicated that Ni(0), Ni­(I), Ni­(II), and Ni­(III) species might be involved in the catalytic cycle.