The enantioselective hydrogenation of ketopantolactone (KPL) on Pt-alumina catalyst modified by β-isocinchonine (β-ICN) and O-phenylcinchonidine (PhOCD) in toluene, acetic acid and their mixtures under otherwise identical experimental conditions was studied. Reversal of the enantioselection was obtained dependent on the concentration of acetic acid (eemax = 17% (S) on Pt-PhOCD and 50% (R) on Pt-β-ICN, respectively). The possible role in enantioselection of adducts forming in the reaction mixture and the stability of PhOCD under the conditions of the hydrogenation was investigated by ESI-MS. The results of the nonlinear phenomenon measurements on β-ICN + PhOCD mixtures suggest that the intermediate surface complexes β-ICN-KPL and PhOCD-KPL responsible for the opposite enantioselection include different types of interactions and the enantioselection is directed by the competition between these interactions.
ASJC Scopus subject areas
- Process Chemistry and Technology