Asymmetric Synthesis of Diphosphine Ligands Containing Phosphorus and Carbon Stereogenic Centers by Means of a Chiral Palladium Complex Promoted Hydrophosphination Reaction

Abstract

An organopalladium complex containing ortho-metalated (R)-(1-(dimethylamino) ethyl)naphthalene as the chiral auxiliary has been used to promote the asymmetric hydrophosphination reaction between diphenylphosphine and phenyldi[(Z)-prop-1-enyl]phosphine in high regio- and stereoselectivity under mild conditions. The hydrophosphination reaction generated only two diastereomers in a ratio of 1:1. The two hydrophosphination products contained both phosphorus and carbon stereogenic centers and were subsequently isolated by fractional crystallization. Their absolute stereochemistries were analyzed by X-ray crystallography. The naphthylamine auxiliary could be removed chemoselectively from the template products by treatment with concentrated hydrochloric acid to form the corresponding optically pure neutral dichloro complexes. Subsequently, the dichloro complexes underwent ligand displacement with aqueous cyanide to generate the optically pure diphosphine ligands in high yields.