Asymmetric Catalysts Containing Phosphinooxazoline Ligands

The unsymmetrical phosphinooxazolines 1 constitute one family of the newest generation of chiral bidentate ligands. These ligands possess a chiral centre on the oxazoline portion and have the opportunity to incorporate a chiral P-centre. As part of a metal complex, the soft donor P-atom is a π-electron acceptor, unlike the hard donor N-atom. Seteroelectronic `trans-influence'dictates that the atom complexed to the metal centre trans to the P-atom is significantly more electrophilic than the one located trans to the N-atom; thus regioselectivity of reactions is inherently increased by the electronic properties of the ligand. To date, the most promising complexes that contain these ligands contain a Cu, W, Pd, Pt, Ru or Ir centre and have been shown to catalyse a variety of reactions (including hydrogenation of ketones, olefins and imines, Diels-Alder reaction) in high yield and enantiomeric excess.