The Effect of the Bite Angle of Diphosphane Ligands on Activity and Selectivity in Palladium-Catalyzed Allylic Alkylation

Abstract

The effect of the natural bite angle (βn) of diphosphane ligands on catalyst selectivity and activity in the palladium-catalyzed allylic alkylation was investigated. The selectivity and rate of the reaction are mainly determined by steric hindrance induced by the diphosphane ligands. The steric hindrance at the palladium center increases as the natural bite angle of the ligand becomes larger. This results in an increasing selectivity at larger bite angles, but at very large bite angles the rate of the reaction drops. The ligand with the largest calculated bite angle, Xantphos, induced 100% selectivity but the reaction rate became low.