ENANTIOSELECTIVE HYDROGENATION OF ETHYL PYRUVATE IN SUPERCRITICAL FLUIDS

The enantioselective hydrogenation of ethyl pyruvate to (R)-ethyl lact ate has been studied using gases under supercritical conditions as sol vents. The catalyst was a 5 wt% Pt/alumina modified with cinchonidine. In supercritical ethane the reaction time could be reduced by a facto r of 3.5 compared to toluene under similar conditions, without any los s in enantioselectivity. A further advantage of ethane is that the ena ntioselectivity remains high even at high catalyst/reactant ratio, whi ch is interesting in view of a possible application of a continuous fi xed-bed reactor for this reaction. A strong catalyst deactivation was observed in supercritical CO2, which is due to the reduction of CO2 on Pt as indicated by FTIR.