Highly Efficient Platinum-Catalyzed Enantioselective Hydrogenation of Trifluoroacetoacetates in Acidic Solvents

The hydrogenation of methyl-, ethyl- and isopropyl-4,4,4-trifluoroacetoacetates to the corresponding chiral trifluoromethyl alcohols has been investigated over Pt/A1₂O₃ modified by O-methyl-cinchonidine. Up to 96% ee and 1850 h^-1 average TOF have been achieved in the synthesis of this important chiral building block. The special role of reaction medium and particularly the impact of water and acids on enantiodiscrimination are discussed.