Three-phenyl transfer in palladium-catalyzed C[sbnd]C coupling reactions by triarylbismuths: A mechanistic study

Abstract

The unusual reactivity of organobismuth compounds in cross-coupling processes, where they act as multi-aryl sources, opens up new and exciting possibilities in the field of organic synthesis. In particular, the high reactivity of arylbismuths in multifold couplings with arylhalides suggests that three catalytic cycles occur simultaneously. Here, we carry out a computational investigation of a cross-coupling model reaction between bromobenzene (Ph-Br) and triphenylbismuthine (Ph3Bi), catalyzed by Pd(0). The energetic profile evidences the exergonic behavior of the overall reaction with a ΔrG of −38.2 kcal mol−1, in good agreement with the experimental results. Moreover, the largest activation energy (39.8 kcal mol−1) is found for the first Ph3Bi aryl transfer (PhP’1Ph1 → PhP’2Ph1), identified as the rate-determining step. Additional dynamical computations on these potential profiles are needed to confirm these findings. We expect this research to allow for a better understanding of organobismuth palladium-catalyzed CC coupling reactions and organobismuth chemistry in general.