Enantioselective hydrogenation of trifluoromethylcyclohexyl ketone on cinchona alkaloid modified Pt-alumina catalyst

The enantioselective heterogeneous catalytic hydrogenation of trifluoromethylcyclohexyl ketone (2), on Pt-alumina (E4759) modified by different chiral compounds in toluene and ethanol solution with and without trifluoroacetic (TFA) has been investigated. The effects of the type of modifiers and their concentration (0-10 mmol/l), hydrogen pressure (1-100 bar), temperature (273-301 K) and conversion on the reaction rate and the enantioselectivity (ee) were studied. The achieved ee was 48% in the case of CD. Depending on solvents the inversion of enantioselectivity was observed. The available information suggests that the compounds responsible for chiral induction are different intermediates, the structure of which depends mostly on the acidic or non-acidic nature of the hydrogenation medium.