Di-Palladium Complexes are Active Catalysts for Mono-N-Protected Amino Acid-Accelerated Enantioselective C-H Functionalization

Abstract

The role of mono-protected amino acid (MPAA) ligands in accelerating enantioselective cyclopalladation and palladium-catalyzed C–H functionalization was investigated using kinetic, spectroscopic, and computational methods. The catalytic relevance of characterized di-palladium species was evaluated by kinetic analysis. The kinetic method of continuous variation (MCV) demonstrated that a complex containing a single MPAA-bridged di-palladium core (Pd2(MPAA)1) is an active catalyst for the reactions studied. The experimental findings are consistent with density functional theory calculations that indicate that enantioinduction can be achieved by a single MPAA ligand bridging a di-palladium catalyst through secondary sphere hydrogen-bonding interactions that lower the barrier to C–H activation of the major enantiomer.