1,2-Bis(diphenylphosphino)-1-cyclohexylethane. A New Chiral Phosphine Ligand for Catalytic Chiral Hydrogenations

Article abstract of DOI:10.1021/jo01313a033

The new chiral bidentate phosphine ligand (R)-1,2-bis(diphenylphosphino)-1-cyclohexylethane ((R)-Cycphos) has been prepared.The rhodium(I) cationic complex of this phosphine serves as an effective homogeneous asymmetric hydrogenation catalyst for the reduction of (Z)-α-amidoacrylic acids at ambient temperature and pressure.Optical yields for the corresponding (S)-α-amino acid derivatives that are produced are generally above 90percent.The success of this ligand in giving higher optical yields than those obtained from other structurally analogous phosphines is rationalized in terms of the bulky cyclohexyl substituent affording a more stereochemically rigid chelating phosphine.