Diphosphonites as highly efficient ligands for enantioselective rhodium-catalyzed hydrogenation

Chiral ligands with achiral backbones such as ethano- or ferroceno-bridges linking two phosphonites derived from chiral diols such as binaphthol (BINOL) have been prepared; the corresponding Rh complexes are excellent catalysts in the hydrogenation of prochiral olefins such as itaconic acid dimethyl ester or 2-acetamido methyl acrylate, the ee values being 90–99.5%.