Rhodium-catalyzed selective direct arylation of phosphines with aryl bromides

The widespread use of phosphine ligand libraries is frequently hampered by the challenges associated with their modular preparation. Here, we report a protocol that appends arenes to arylphosphines to access a series of biaryl monophosphines via rhodium-catalyzed P(III)-directed ortho C-H activation, enabling unprecedented one-fold, two-fold, and three-fold direct arylation. Our experimental and theoretical findings reveal a mechanism involving oxidative addition of aryl bromides to the Rh catalyst, further ortho C-H metalation via a four-membered cyclometalated ring. Given the ready availability of substrates, our approach opens the door to developing more general methods for the construction of phosphine ligands. The widespread use of biaryl monophosphines is frequently hampered by the challenges associated with their modular preparation. Here, the authors report a protocol that appends arenes to arylphosphines to access a series of these compounds via rhodium-catalysed P(III)- directed ortho C-H activation, enabling one-fold, two-fold, and threefold direct arylation.