The enantioselective hydrogenation of ethyl pyruvate to (S)-ethyl lactate over cinchonine- and α-isocinchonine-modified Pt/Al2O3 catalysts was studied as a function of modifier concentration and reaction temperature. The maximum enantioselectivities obtained under the applied mild conditions were 89% ee using cinchonine (0.014 mmol dm-3, 1 bar H2, 23 °C, 6% AcOH in toluene), and 76% ee in the case of α-isocinchonine (0.14 mmol dm-3, 1 bar H2 - 10°C, 69t AcOH in toluene). Since α-isocinchonine of rigid structure exists only in "anti-open" conformation these data provide additional experimental evidence to support the former suggestion concerning the dominating role of "anti-open" conformation in these cinchona-modified enantioselective hydrogenations.
- Ethyl pyruvate
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