Synthesis of Exclusively Centrostereogenic 1,3-Bidentate Ferrocenyldiphosphane Ligands and Their Use in Enantioselective Hydrogenations

Five representatives of a novel class of 1,3-bidentate and exclusively centrostereogenic ferrocenyldiphosphane ligands were prepared from ferrocene in a five-step sequence. The ligands were tested in rhodium-mediated asymmetric hydrogenations of two alkenes (methyl acetamidocinnamate and dimethyl itaconate) and delivered high product enantioselectivities of up to 96% ee. The coordination behavior of one ligand in its square-planar palladium dichloride complex was studied by X-ray diffraction, and the R absolute configuration was determined from the X-ray anomalous dispersion effects.