Enantioselective hydrogenation of ethyl pyruvate

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

“…Fig. 1 not only verifies the existence of the ITP, but also demonstrates that, in the case of hydrogenation in toluene at a DHCD concentration of 0.001 mmol/L, ee and ee also increase continuously above 20% conversion, except for hydrogenation at 296 K. At 296 K, over ∼ 10% conversion (time of reaction is 2-3 min) ee decreases, probably because-due to hydrogenation of the quinoline skeleton of DHCD [21,[25][26][27][28]; the concentration of DHCD responsi- ble for enantioselection also decreases (Fig. 1).…”

“…According to our preliminary experiments, measurements within the kinetic range may be carried out under the following experimental conditions: E4759 25 mg, hydrogen 1 bar, [DHCD] 0.001-0.1 mmol/L, EtPy ∼ 1 mM, Before discussion of the results it is necessary to mention that in studies on the reaction mechanism it was found that the modifier is also converted in the course of hydrogenation [21,[25][26][27][28], in the presence of EtPy, however, this hydrogenation can be suppressed. The slowdown of hydrogenation and the decrease in ee as a function of the duration of catalyst pretreatment in the presence of DHCD are well demonstrated in Table 2 (entries 1-4).…”

Untitled

“…Studies in nonacidic media [8,11], particularly in dichloromethane [7], cannot give reliable information on the intrinsic rate acceleration induced by the chiral modifier. A recent illustration of the role of acids was provided by the hydrogenation of EP on Pt/zeolite, for which a continuous loss of activity was observed in cyclohexane but improved long-term performance could be achieved by increasing the acidity of the zeolite or changing the solvent to acetic acid [12].…”

Effective and Reusable Pt Catalysts Supported on Periodic Mesoporous Resols for Chiral Hydrogenation

“…New types of catalysts such as platinum colloids [19] and Pt particles supported on inorganic materials other than Al 2 O 3 and SiO 2 have also been explored at around the same time. Moderate to good enantiomeric excesses (ees) were obtained with Pt/MCM-41 [20][21][22], Pt/HNaY [23], Pt/clay [24,25], Pt/LDH [26], and Pt/SWNTs catalysts [27].…”