First Enantioselective Hydrogenation of a Trifluoro-β-ketoester with Cinchona-Modified Platinum

A series of trifluoromethyl ketones possessing different functional groups were hydrogenated over Pt/Al2O3 modified by cinchonidine and O-methylcinchonidine. The highest enantiomeric epcess of 90% was achieved in the hydrogenation of ethyl 4,4,4-trifluoroacetoacetate. The remarkable variation of enantioselectivity in the synthesis of various α,α,α-trifluoromethyl alcohols is interpreted by electronic and steric effects. Future mechanistic studies have to clarify the unexpectedly big influence of acidic solvent and the special role of the (C9)–OH group in cinchonidine.