Nickel-Catalyzed Diversification of Phosphine Ligands by Formal Substitution at Phosphorus

We report a general diversification strategy for phosphines that enables the rapid discovery of new ligands. Alkylated phosphonium salts, prepared by standard alkylation of phosphines, are selectively dearylated in a nickel-catalyzed process to access alkylated phosphine products via a formal substitution at the phosphorus center. The reaction can be used to introduce a wide range of alkyl substituents into both mono- and bisphosphines. We also show that the alkylation and dearylation steps can be conducted in a one-pot sequence, enabling accelerated access to underexplored ligand space. The phosphine products of the reaction are converted in situ to air-stable borane adducts for isolation, and versatile derivatization reactions of these adducts are demonstrated.