ENANTIODIFFERENTIATION IN ASYMMETRIC SONOCHEMICAL HYDROGENATIONS

The effect of sonochemical pretreatment on the enantioselectivity of P t/Al2O3-cinchonidine-catalyzed ethyl pyruvate hydrogenation was studie d at different hydrogen pressures in various solvents, mainly in aceti c acid. The sonochemical pretreatment of a commercial Pt/Al2O3-cinchon idine catalytic system in acetic acid resulted in enhanced enantiosele ctivity providing excellent ee values (97% ee) under mild and widely v aried experimental conditions. Moreover, the application of ultrasonic s provides a possibility of the catalyst recycling without regeneratio n. The catalyst was tested by transmission electron microscopy to dete rmine the effect of the sonication on the metal particle size morpholo gy.