Rhodium-catalyzed selective direct arylation of phosphines with aryl bromides

Abstract

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.

Aryl Triflates in Phosphorus-Directed Rhodium(III)-Catalyzed C–H Activation

“…As a white solid (80%, 85 mg) 1 H NMR (500 MHz, CDCl3): δ (ppm) = 7.50 (dd, J = 8.8, 5.2 Hz, 2H), 7.07 (s, 1H), 7.03 (t, J = 8.7 Hz, 2H), 2.45 (s, 3H). 19 F{ 1 H} NMR (470 MHz, CDCl3): δ (ppm) = -112.9 (s).…”

“…The steric congestion from polyaromatic triflates did not hampered the reaction, and in the presence of 2naphthyl, 1-naphthyl or 9-phenanthrenyl groups the corresponding coupling products 13 (89%), 14 (32%) and 15 (76%) were obtained (Figure 2). Our protocol was successfully extended to other PAH dimonophosphines (17)(18)(19), Figure 3). 1-Naphthyl diphenylphosphine gave 88%, 93% and 55% isolated yield for 20, 21 and 22, respectively, in the presence of electronwithdrawing groups (with acetyl, nitrile and trifluoromethyl groups, respectively), and 87%, 55% and 51% for 23, 24 and 25 respectively, in the presence of electron-rich triflate as coupling…”

Metal-Free Phosphination and Continued Functionalization of Pyridine: A Theoretical Study

“…In light of their fundamental importance, many methods of C-P bond formation have been developed [ 4 , 5 , 6 ]. Among these methods, transition-metal-catalyzed cross-coupling reactions, including the Pd- [ 7 ], Cu- [ 8 ], Zn- [ 9 ], Ni- [ 10 ], Mn- [ 11 ], Ag- [ 12 ], and Rh-catalyzed [ 13 ] phosphination reactions of various aryl partners with phosphine reagents, have received great attention [ 14 ]. In particular, researchers have focused on developing a mild, efficient, and environmentally benign method of C–P bond formation [ 15 , 16 , 17 ].…”

Ligand-Determined Single, Double, and Triple C–H Arylation of Aryl Phosphines at Will

“…This revolutionary synthetic strategy could provide unusual strategic disconnections for the construction of hard-to-form bonds and has been gradually applied in the exploitation of pharmaceuticals and organic functional materials. , Nevertheless, it has been relatively less used in the buildup of ligand banks. , We envisioned that the P­(III)-directed ortho -C–H arylation of aryl phosphines could provide an ideal approach to modular synthesis of biaryl phosphines with different electronic and steric properties (Scheme c). However, to implement this blueprint, several challenges have to be resolved: (i) While the ortho -C–H metalation of aryl phosphines forming strained four-membered metallacycles has long been known, the precedents for catalytic variants are rather limited (mostly on C–H borylation and silylation), − , probably owing to the thermodynamic instability of small ring intermediates. The reported ortho -C–H functionalizations of phosphorus compounds typically require the oxidization of P­(III) to a P­(V) directing group, which suffers from troublesome protection–deprotection procedures .…”