Asymmetric nickel-catalyzed hydrocyanation of vinylarenes by applying homochiral xantphos ligands

New homochiral xantphos-type diphosphonite ligands with binaphthosv substit uents have been prepared and characterized by NMR spectroscopy. These ligan ds have been applied in the nickel-catalyzed hydrocyanation of styrene and ether vinylarenes Enantioselectivities up to 63 % ee have been obtained hv using 4-isobutylstyrene as a substrate, Addition of an excess of ligand str ongly inhibits the hydrocyanation reaction since the bis-chelate nickel com plexes formed are highly stable and catalytically inactive.