Asymmetric Hydrogenation of Ethyl Pyruvate: Relationship between Conversion and Enantioselectivity

New data on enantiomeric excess versus conversion during enantioselective hydrogenation of activated ketones on a platinum catalyst

“…The phenomenon was later investigated by several research groups and diverse conclusions were drawn depending on the experimental conditions (Table 1). After reviewing the experimental results and completing various novel experiments, Blackmond and co-workers [9,10] and Margitfalvi et al [12], on the one hand, and Baiker and co-workers [13] on the other, proposed explanations for the ITP. According to the former authors [9,10,12], a change in ee versus conversion is an intrinsic feature of the catalytic system, whereas in the opinion of the latter authors [13], the phenomenon is caused mainly by impurities.…”

“…After reviewing the experimental results and completing various novel experiments, Blackmond and co-workers [9,10] and Margitfalvi et al [12], on the one hand, and Baiker and co-workers [13] on the other, proposed explanations for the ITP. According to the former authors [9,10,12], a change in ee versus conversion is an intrinsic feature of the catalytic system, whereas in the opinion of the latter authors [13], the phenomenon is caused mainly by impurities. Publication of the different interpretations was followed by a dispute [15,16]; however, it has not been decided to date [17] whether the initial increase in ee with conversion is a "reaction-driven" phenomenon or is due to the presence of impurities in the system.…”

“…One such problem is the reason for the rapid increase in enantioselectivity (ee) in the initial transient period (ITP) of the conversion. Details of previous studies in this field (Table 1 [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]) are reviewed in the Discussion of the present work.…”

“…It was established at an early stage of research that the efficiency of chiral hydrogenation is significantly affected not only by the experimental parameters, which play a decisive role, but also by the methods of execution [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In general, four different methods and their variants [1,2] have been adopted for performing liquid-phase chiral hydrogenation:…”

Enantioselective hydrogenation of ethyl pyruvate over cinchonidine-Pt/Al2O3 catalyst. A reaction kinetic approach

“…The maximum rate was measured in the 10-40 min and depended on the experimental condition of the enantioselective hydrogenation. The maximum rates exceeded the initial rate by 5-30% [13].…”