Bisphosphines: A Prominent Ancillary Ligand Class for Application in Nickel-Catalyzed C-N Cross-Coupling

The Ni-catalyzed Csp2N cross-coupling of NH substrates and (hetero)aryl (pseudo)halides for the synthesis of (hetero)anilines is in the midst of a resurgence. Reactivity breakthroughs that have been achieved in this field within the past five years have served to establish Ni catalysis as being competitive with, and in some cases superior to, more well-established Pd- or Cu-based protocols. Whereas the repurposing of useful ancillary ligands from the Pd domain has been the most frequently employed approach in the quest to develop effective Ni-based catalysts for such transformations, considerable progress has been made as of late in the design of ancillary ligands tailored specifically for use with Ni. Bisphosphine ancillary ligands have proven to be well-suited for such an approach, given their modular and facile syntheses; several variants have emerged recently that are particularly effective in enabling a range of otherwise challenging Ni-catalyzed Csp2N cross-couplings. This Perspective presents a comprehensive summary of the advancements within the field of Ni-catalyzed Csp2N cross-coupling through the application of the bisphosphine ancillary ligand class. It is our intention that the discussion of key ancillary ligand design concepts and mechanistic considerations presented herein will provide a useful platform for researchers to initiate ancillary ligand design efforts for the development of high-performing Ni cross-coupling catalysts.