687-47-8Relevant articles and documents
Asymmetric hydrogenation of ethyl pyruvate using layered double hydroxides-supported nano noble metal catalysts
Kantam, Mannepalli Lakshmi,Kumar, Karasala Vijaya,Sreedhar, Bojja
, p. 959 - 964 (2007)
Layered double hydroxide (LDH)-supported nano noble metal heterogeneous catalysts are synthesized by ion exchange of K2PtCl6, Na2PdCl4 and impregnation of RhCl3.3H2O followed by reduction with H2. The LDH-Rh, Pt, and Pd catalysts are tested in the enantioselective hydrogenation of ethyl pyruvate to ethyl lactate with very good yields and enantiomeric excess's (e.e.'s) of up to 72% were obtained with Pt. The catalyst was recovered and reused for several cycles with consistent activity. Copyright Taylor & Francis Group, LLC.
Stereochemical Control in Microbial Reduction. XXI. Effect of Organic Solvents on Reduction of α-Keto Esters Mediated by Bakers' Yeast
Nakamura, Kaoru,Kondo, Shin-ichi,Kawai, Yasushi,Ohno, Atsuyoshi
, p. 2738 - 2743 (1993)
Reduction of α-keto esters mediated by bakers' yeast takes place in an organic solvent without immobilization of the microbe.Several factors such as water content, pH of the solution, amount of bakers' yeast, and the property of the organic solvent affect to enantioselectivity of the reduction.In benzene, stereochemistry of the reduction shifts markedly toward preferential production of the (R)-α-hydroxy ester.The stereochemical consequence of the present reaction is accounted for by two factors; 1) the inhibition of enzymatic decomposition of the produced (R)-α-hydroxy ester in benzene and 2) the enhancement of relative activities of dehydrogenases or reductases in producing the (R)-α-hydroxy ester under dilute concentrations of the substrate at the vicinity of enzymes.
REDUCTION BY BAKERS' YEAST IN BENZENE
Nakamura, Kaoru,Kondo, Shin-ichi,Kawai, Yasushi,Ohno, Atsuyoshi
, p. 7075 - 7078 (1991)
Reduction of α-keto esters by non-immobilized bakers' yeast in an organic solvent is reported.When benzene is employed as the solvent, the reduction tends to afford the corresponding (R)-hydroxy ester predominantly.Key Words: bakers' yeast; asymmetric reduction; organic solvent; stereochemical control; α-keto ester; α-hydroxy ester
Enantioselective hydrogenation of ethyl pyruvate catalyzed by alumina support rhodium modified with quinine
Xiong, Wei,Ma, Hongxia,Hong, Yanyi,Chen, Hua,Li, Xianjun
, p. 1449 - 1452 (2005)
Alumina supported rhodium catalyst using cinchonidine as a stabilizer exhibited excellent performance in the asymmetric hydrogenation of ethyl pyruvate with the addition of quinine. Quinine as a chiral modifier can not only induce the enantioselectivity, but also greatly accelerate the reaction. Under the optimum conditions: 293 K, 7.0 MPa of hydrogen pressure and 4.6 × 10-3 mol/L of quinine concentration in THF, TOF of Rh/2(cinchonidine)-γ-Al2O3 as catalyst and ee value of (R)-ethyl lactate can achieve 894 h-1 and 71.6% ee, respectively.
Continuous platinum-catalyzed enantioselective hydrogenation in 'supercritical' solvents
Wandeler,Kuenzle,Schneider,Mallat,Baiker
, p. 673 - 674 (2001)
Hydrogenation of ethyl pyruvate in 'supercritical' ethane in a fixed bed reactor over cinchona-modified Pt/Al2O3 affords good ee at an exceptionally high rate, whereas in carbon dioxide the catalytic performance under similar conditions is inferior.
Improvement of the enantioselectivity in the enantioselective hydrogenation of ethyl pyruvate by addition of achiral tertiary amines
Margitfalvi, Jozsef L.,Talas, Emilia,Hegedus, Mihaly
, p. 645 - 646 (1999)
In the asymmetric hydrogenation of ethyl pyruvate over the catalyst system cinchonidine-Pt/AI2O3 the enantioselectivity was significantly improved by addition of different achiral tertiary amines to the reaction mixture, however the effect appeared to be strongly solvent and concentration dependent.
A new cinchona-modified platinum catalyst for the enantioselective hydrogenation of pyruvate: The structure of the 1:1 alkaloid-reactant complex
Bartok, Mihaly,Felfoeldi, Karoly,Toeroek, Bela,Bartok, Tibor
, p. 2605 - 2606 (1998)
The hydrogenation of ethyl pyruvate to (S)-ethyl lactate (up to 70% ee) over a Pt/A12O3 catalyst using α-isocinchonine as a modifier strongly supports the structure of the intermediate complex [cinchona alkaloid (open conformer)-pyruvate 1:1 complex] of this type of reactions.
Enantioselective hydrogenation of ethyl pyruvate catalyzed by α- and β-isocinchonine-modified Pt/Al2O3 in acetic acid
Bartok, Mihaly,Sutyinszki, Maria,Felfoeldi, Karoly
, p. 207 - 214 (2003)
The enantioselective hydrogenation of ethyl pyruvate (EtPy) was studied on Pt-alumina catalysts modified by high-purity α-isocinchonine (α-ICN) and β-isocinchonine (β-ICN) in AcOH. The effect of the modifier concentration, temperature, and hydrogen pressure on the reaction rate and the enantioselectivity was examined. Using the Engelhard 4759 catalyst under medium experimental conditions (273 K, hydrogen pressure of 25 bar, α-ICN concentration of 1 mmol/L) an optical yield of 93-94% can be achieved. In the case of β-ICN, maximum ee is 70-72% (297 K, 20 bar, β-ICN concentration of 1 mmol/L); at the same time, the rate of EtPy hydrogenation is higher than in the case of dihydrocinchonine (DHCN) or α-ICN. Chiral modifiers themselves are converted under the conditions of hydrogenation. The results of ESI-MS, ESI-MS-MS, HPLC-MS, and desorption measurements strongly suggest that α-ICN and β-ICN compounds with a rigid structure are responsible for chiral induction, since DHCN and hydrogenated products of DHCN were not identifiable among the reaction products. These experimental results support the earlier assumption that it is cinchona alkaloids in the "open 3" (in another terminology "antiopen") conformation that participate in enantioselection. However, based on other experimental observations of this work, the participation of other, so far unknown factors in enantioselection may not be excluded either.
Asymmetric hydrogenation on platinum: Nonlinear effect of coadsorbed cinchona alkaloids on enantiodifferentiation
Huck,Buergi,Mallat,Baiker
, p. 276 - 287 (2003)
Prominent nonlinear effects in enantioselectivity were observed with a transient technique when ethyl pyruvate was hydrogenated over Pt/Al 2O3 in the presence of two cinchona alkaloids, which alone afford the opposite enantiomers of ethyl lactate in excess. The changes in reaction rate and ee, detected after injection of the second alkaloid, varied strongly with type and amount of the alkaloid, and with the order of their addition to the reaction mixture. For example, under ambient conditions in acetic acid cinchonidine (CD) afforded 90% ee to (R)-ethyl lactate and addition of equimolar amount of quinidine (QD) reduced the ee to (R)-ethyl lactate only to 88%, though QD alone provided 94% ee to (S)-lactate in a slightly faster reaction. The stronger adsorption of CD on Pt in the presence of hydrogen and acetic acid was proved by UV-vis spectroscopy. The different adsorption strengths result in an enrichment of CD on the Pt surface and also in a crucial difference in the dominant adsorption geometries. CD is assumed to adsorb preferentially via the quinoline rings laying approximately parallel to the Pt surface. In this position it can interact with ethyl pyruvate during hydrogen uptake and control the enantioselectivity. The weaker adsorbing QD adopts mainly a position with the quinoline plane being tilted relative to the Pt surface and these species are not involved in the enantioselective reaction. Competing hydrogenation of the alkaloid, and steric and electronic interactions among the adsorbed species, can also influence the alkaloid efficiency and the product distribution. Hydrogenation of the quinoline rings at low alkaloid concentration resulted in unprecedented swings in the enantiomeric excess.
Mesoporous silica-supported Pt catalysts in enantioselective hydrogenation of ethyl pyruvate
Chung, Iljun,Kim, Jeongmyeong,Song, Byeongju,Yun, Yongju
, (2020)
Catalytic properties of Pt catalysts supported on mesoporous silica (Pt/m-SiO2) have been studied in enantioselective hydrogenation of ethyl pyruvate. The influences of pore structure of mesoporous silica (m-SiO2), type of chiral modifier, and H2 pressure on the catalytic performance have been investigated by using various m-SiO2 supports and cinchona alkaloids and by varying H2 pressure. The use of MCM-41, SBA-15, KIT-6, and MCF reveals that characteristic pore structure and size of m-SiO2 supports significantly affect both activity and enantioselectivity. A facile diffusion of chiral modifier through large mesopores of MCF support enables Pt/MCF to exhibit excellent performance. A comparison of the efficiency of cinchona alkaloids-modified Pt catalysts shows that QN and QD lead to higher performance than CD and CN at ambient H2 pressure. The influence of cinchona alkaloids on enantioselectivity noticeably depends on H2 pressure. Cinchona alkaloid-modified Pt/m-SiO2 exhibit superior enantioselectivity to the corresponding Pt/Al2O3 under various H2 pressures. These results imply that m-SiO2 is a promising support and that fine control of pore structure can further improve catalytic performance of Pt/m-SiO2 in heterogeneous enantioselective hydrogenation.
