Preparation of a Highly Congested Carbazoyl-Derived P,N-Type Phosphine Ligand for Acetone Monoarylations

We report a newly developed carbazoyl-derived
P,N-type phosphine
ligand (L1) for the monoarylation of acetone with aryl
chlorides. The proposed Pd­(dba)2/L1 catalyst
exhibited remarkable catalytic reactivity toward highly electron rich
and sterically congested aryl chlorides, with catalyst loading as
low as 0.1 mol % of Pd along with excellent chemoselectivity. A reaction
rate study of the system using electronically diverse aryl chlorides
determined the mechanisms regarding the rate-limiting steps in this
reaction. The oxidative addition adduct of Pd-PhenCar-Phos with p-chlorotoluene showed the participation of N–Pd
coordination in the metal complex. The isolated palladium complex C1 could be utilized as a precatalyst in the transformation
and achieved performance comparable to that of the in situ generated
palladium species.