Asymmetric nickel-catalyzed hydrocyanation of vinylarenes by applying homochiral xantphos ligands.
New homochiral xantphos-type diphosphonite ligands with binaphthoxy substituents have been prepared and characterized by NMR spectroscopy. These ligands have been applied in the nickel-catalyzed hydrocyanation of styrene and other vinylarenes. Enantioselectivities up to 63% ee have been obtained by using 4-isobutylstyrene as a substrate. Addition of an excess of ligand strongly inhibits the hydrocyanation reaction since the bis-chelate nickel complexes formed are highly stable and catalytically inactive.
Goertz
W
W
Goldschmidt AG, Central Research, Essen, Germany.
Kamer
P C
PC
van Leeuwen
P W
PW
Vogt
D
D