Asymmetric hydrogenation of alpha,beta-unsaturated carboxylic acids catalyzed by ruthenium(II) complexes of spirobifluorene diphosphine (SFDP) ligands

摘要

The ruthenium diacetate complexes ligated by chiral spirobifluorene diphosphines (SFDP) were very effective catalysts for the asymmetric hydrogenation of tiglic acid derivatives and alpha-methylcinnamic acid derivatives with high activities and excellent enantioselectivities (up to 98 % ee). The alpha-aryloxybutenoic acids can also be hydrogenated by these catalysts to provide the corresponding saturated alpha-aryloxybutanoic acids in high yields (89-93 %) and enantioselectivities (up to 95 % ee). In this reaction, the SFDP ligand with para-methyl groups on the P-phenyl rings gave the best results.