Enantioselective hydrogenation of beta-keto esters catalyzed by chiral binaphthylbisphosphine ruthenium complexes

Thr catalytic activity and the enantioselectivity manifested by cationic ch iral binaphthylbisphosphine ruthenium complexes in asymmetric hydrogenation of beta-keto esters were studied. The effects of the nature of the solvent , the reaction temperature, the pressure, addition of acids, and the reagen t ratio on the yield and the degree of enantiomeric enrichment of the react ion products were examined. For hydrogenation of ethyl 3-chloroacetoacetate to form (R)- or (S)-enantiomers of ethyl 4-chloro-3-hydroxybutyrate. condi tions were found which allow one to quantitatively prepare this valuable sy nthon with high enantiomeric purity (97-99%) at a low concentration of the catalyst (the ratio substrate : Ru = 10000).