A Novel Axially Chiral Phosphine-Oxazoline Ligand with an Axis-Unfixed Biphenyl Backbone: TPreparation, Complexation, and Application in an ­Asymmetric Catalytic Reaction

A novel chiral phosphine-oxazoline ligand 3 with an axis-unfixed biphenyl backbone was prepared. This ligand existed as a mixture of two diastereomers in equilibrium in solution. However, when it was coordinated with palladium(II), only one of the two kinds of possible diastereomer complexes with different axial chirality was formed. When this axis-unfixed chiral ligand was used, up to 90% ee was attained for the palladium-catalyzed asymmetric allylic alkylation.