Chiral diphosphine ligands based on an arene chromium tricarbonyl scaffold: a modular approach to asymmetric hydrogenation

A planar-chiral diphosphine ligand-class based on an arene chromium tricarbonyl backbone has been devised featuring a modular architecture that allows for the synthesis of a broad ligand library. The substituents on the donor phosphorus atoms contain aliphatic, alicyclic and aromatic groups of different kinds. A (R,R)-2,5-dimethylphospholane moiety is also included. That library has been subdued to a ligand profiling by employment in a number of homogeneous enantioselective hydrogenations including substrates with C=C, C=N and C=O double bonds. These reactions are described and the results are evaluated and discussed.