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.
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
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.
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.
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.
Enantioselective hydrogenation of α-keto esters over cinchona-Pt/Al2O'3 catalyst. Kinetic evidence for the substrate-modifier interaction in the liquid phase
Margitfalvi,Hegedus,Tfirst
, p. 571 - 580 (1996)
The hydrogenation of ethyl pyruvate was studied over cinchonidine-Pt/Al2O3 catalyst. Contrary to earlier results it has been found that the initial enantiomeric excess extrapolated to zero conversion is close to zero. Based on kinetic analysis the results are considered as indirect evidence for the substrate-modifier interaction taking place in the liquid phase. The above interaction leads to the formation of a weak substrate-modifier complex. The formation of the complex in the liquid phase is the key step to control both the rate acceleration and the induction of enantio-differentiation in the hydrogenation of α-keto esters in the presence of cinchona-Pt/Al2O3 catalysts. The character of interactions in the substrate-modifier complex is discussed. By using molecular modelling the possible form of the complex is also given.
Solvothermal Alcoholysis Routes for Recycling Polylactide Waste as Lactic Acid Esters
Petrus, Rafal,Bykowski, Dominik,Sobota, Piotr
, p. 5222 - 5235 (2016)
In this work, we investigated the possible use of polylactide (PLA), a biodegradable polymer obtained from renewable biofeedstock, to produce a range of industrially useful lactic acid esters. We describe a simple and convenient solvothermal alcoholysis method for large-scale recycling of PLA resins or residues from disposable packaging in the presence of the appropriate alcohol under catalyst-free or catalytic conditions. This process proceeds easily both without and with a catalyst. The results show that the best catalytic activities involve magnesium and calcium alkoxides synthesized in situ from organometallic or metallic precursors and an alcohol. We determined the crystal structure of the chiral mononuclear postcatalyst [Ca(LAc)2(EL)2] (1; LAc = lactic acid anion, EL = ethyl lactate), obtained directly from the reactor. Particular emphasis is placed on the operating conditions and high activity of the catalyst used. Key factors that affect the catalytic activity and reaction mechanism are also highlighted.
Remarkable particle size effect in Rh-catalyzed enantioselective hydrogenations
Hoxha, Fatos,van Vegten, Niels,Urakawa, Atsushi,Krumeich, Frank,Mallat, Tamas,Baiker, Alfons
, p. 224 - 231 (2009)
A series of 0.5-4.3 wt% Rh/Al2O3 catalysts were prepared by flame synthesis. STEM indicated relatively narrow particle size distributions for all catalysts and the mean particle size increased almost linearly with the Rh content in the range 0.96-1.65 nm. A DRIFTS study of CO adsorption on as prepared Rh/Al2O3 and after heat treatment in hydrogen at 400 °C revealed that there was no Rh oxide present at the catalyst surface after the high temperature reduction, which procedure is commonly used prior to enantioselective hydrogenation. In the hydrogenation of ethyl pyruvate and ethyl 3-methyl-2-oxobutyrate the cinchona-modified 4.3 wt% Rh/Al2O3 gave considerably higher ee than those achieved with the best known Rh catalyst. A decrease of the metal loading and thus the mean Rh particle size, led to a loss of ee to (R)-lactate by a factor of up to seven at 1 bar and up to two at 10-100 bar. Our interpretation is that the performance of Rh/Al2O3 is strongly distorted at atmospheric pressure by catalyst deactivation due to the Al2O3-catalyzed aldol condensation of the substrate. During the fast reactions at 100 bar the contribution of strongly adsorbed impurities is small and the variation of ee is mainly due to an intrinsic particle size effect. The structure sensitivity observed under optimal conditions, at high surface hydrogen concentration, is mainly due to steric effects: a small, ca. 1 nm Rh particle cannot accommodate the enantiodifferentiating diastereomeric substrate-modifier complex and the hydrogenation on its surface leads to racemic product. A practical conclusion is that there is no advantage of using small nanoparticles and low metal loading in the enantioselective hydrogenation of α-ketoesters.
1-Naphthyl-1,2-ethanediol as a new chiral modifier of platinum in the enantioselective hydrogenation of activated ketones
Marinas, Alberto,Mallat, Tamas,Baiker, Alfons
, p. 666 - 669 (2004)
1-Naphthyl-1,2-ethanediol (NED) is shown to be a useful modifier in the hydrogenation of ketopantolactone and ethyl-4,4,4-trifluoroacetoacetate under mild conditions. It represents the first effective chiral nonamine-type modifier of Pt for the enantioselective hydrogenation of activated ketones. The enantio-differentiation is attributed to substrate-modifier interactions involving hydrogen bonding between the keto-carbonyl O atom and one or two OH groups of NED. Prominent nonlinear behavior was observed when mixtures of (S)-NED and (R)-2-(1-pyrrolidinyl)-1-(1-naphthyl)ethanol {(R)-PNE} were applied as chiral modifiers. The phenomenon is traced to stronger adsorption of PNE on the metal surface, despite the identical "anchoring moiety" (naphthalene ring) of the two modifiers.
Enantioselective heterogeneous catalysis. I. A working model for the catalyst:modifier:substrate interactions in chiral pyruvate hydrogenations
Augustine,Tanielyan,Doyle
, p. 1803 - 1827 (1993)
The room temperature and atmospheric pressure hydrogenation of ethyl pyruvate over Pt/Al2O3 catalysts modified by varying amounts of dihydrocinchonidine was examined. Data were obtained which showed that the hydrogenation occurred on the corner atoms and adatoms on the Pt crystallites in the catalyst. The formation of (S) ethyl lactate was observed when very low concentrations of the alkaloid modifier were used while at higher modifier concentrations the (R) lactate was produced. The formation of the (R) lactate was accompanied by an increase in the hydrogenation rate. A working hypothesis was formulated to explain these results and to serve as a model for the design of future experiments. This model suggested that the initial adsorption of the dihydrocinchonidine takes place on the face atoms adjacent to the corner atoms on the metal crystallite. This will place the chiral portion of the alkaloid close to the corner atom active site. Enantioselective pyruvate adsorption would be vacilitated by a hydrogen bond between the C9 OH of the alkaloid and the ethoxy oxygen of the pyruvate and hydrogenation of the keto group will lead to (S) lactate formation. In order to place the chiral portion of the modifier near an adatom it is proposed that the alkaloid is adsorbed in an edge-on manner on the face near the adatom active site. In this way the modifier can interact directly with the pyruvate to change its adsorption characteristics. This will lead to an increase in reaction rate and the formation of the (R) lactate.
Preparation method of (R)-(+)-2-p-hydroxyl phenoxyl propionic acid
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Paragraph 0045; 0046, (2018/11/22)
The invention relates to a preparation method of (R)-(+)-2-p-hydroxyl phenoxyl propionic acid. The method comprises the following steps of taking (S)-(-)-lactic acid as a raw material, and performingthree-step reaction, i.e., esterification, nucleophilic substitution and hydrolysis to obtain a target compound. A synthetic process for the (R)-(+)-2-p-hydroxyl phenoxyl propionic acid is further optimized, and the optimum reaction condition and reagent are screened. According to the preparation method designed in the invention, the reaction steps are shortened, and the yield and optical purity of the (R)-(+)-2-p-hydroxyl phenoxyl propionic acid are improved.
13C MR Hyperpolarization of Lactate by Using ParaHydrogen and Metabolic Transformation in Vitro
Cavallari, Eleonora,Carrera, Carla,Aime, Silvio,Reineri, Francesca
supporting information, p. 1200 - 1204 (2017/02/05)
Hyperpolarization of the13C magnetic resonance signal of l-[1–13C]lactate has been obtained using the chemically based, cost-effective method called parahydrogen-induced polarization by means of side-arm hydrogenation (PHIP–SAH). Two ester derivatives of lactate were tested and the factors that determine the polarization level on the product have been investigated in detail. The metabolic conversion of hyperpolarized l-[1–13C]lactate into pyruvate has been observed in vitro using lactate dehydrogenase (LDH) and in a cells lysate. From the acquisition of a series of13C NMR spectra, the metabolic build-up of the [1–13C]pyruvate signal has been observed. These studies demonstrate that, even if the experimental set-up used for these PHIP–SAH hyperpolarization studies is still far from optimal, the attained polarization level is already sufficient to carry out in vitro metabolic studies.
