Palladium-Catalyzed Asymmetric Allylic Substitution Reactions Using New Chiral Phosphinite−Oxazoline Ligands Derived from d-Glucosamine

Abstract

Novel 2-alkyl- or 2-aryl-4,5-(4,6-O-benzylidene-3-O-(diphenylphosphino)-1,2-dideoxy-α-d-glucopyrano)-[2,1-d]-2-oxazolines (5a−f) have been prepared from d-glucosamine hydrochloride. They work effectively as chiral ligands and provide a high level of enantiomeric excess in palladium-catalyzed allylic alkylation and amination reactions. The allylic alkylation of 1,3-diphenyl-3-acetoxyprop-1-ene with dimethyl malonate proceeds smoothly in the presence of 0.25 mol % [Pd(η3-C3H5)Cl]2 and the chiral ligand 5a having the smallest substituent on oxazoline at 0 °C within 6 h to furnish the highest enantiomeric excess (96% ee). The ligand 5a is also effective for the Pd-catalyzed amination of ethyl 1,3-diphenylprop-2-enyl carbonate, leading to the corresponding allylic amine in 94% ee. The full scope and limitations using ligands 5a−f in the allylic substitution reactions are described.