P-Chirogenic Diphosphazanes with Axially Chiral Substituents and Their Use in Rh-Catalyzed Asymmetric Hydrogenation

Abstract

A convenient synthesis of enantiopure P-chirogenic diphosphazanes incorporating bulky bisphenol and 1,1'-bi-2-naphthol-derived substituents via the functionalization of a readily accessible enantiopure lithium phosphinoamide with chlorophosphoridites was developed. Since the product requires no subsequent deprotection, the protocol provides an easy, convenient synthesis of P-chirogenic ligands on the gram scale. The ligands were applied in the Rh-catalyzed asymmetric hydrogenation of benchmark substrates furnishing enantiomeric excess values up to 96%.