Phosphine–Borane Ligands Induce Chemoselective Activation and Catalytic Coupling of Acyl Chlorides at Palladium

Abstract : Acyl chlorides are highly reactive and widely used substrates in catalytic cross-coupling reactions, but so far, site selectivity over other functional groups has remained an issue. In this work, Pd complexes deriving from the phosphine-boranes [i-Pr2P(o-C6H4)](2)BFXyl and i-Pr2P(o-C6H4)-BFXyl(2) (Fxyl = 3,5-(F3C)(2)C6H3) were found to preferentially activate acyl chlorides over C-I, C-Br, C-Cl, C-OTf, and C-OTs bonds. The system is amenable to catalysis (Stille and Negishi couplings), providing a simple and efficient means to forge C(=O)-C bonds in a site-selective manner and to readily access functionalized ketones. To gain insight into the role and influence of the ambiphilic ligands, key Pd complexes have been authenticated and the reaction profiles have been analyzed by density functional theory (DFT) calculations.