cas 687-47-8, Ethyl L(-)-lactate | Articles data

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Asymmetric hydrogenation of ethyl pyruvate using layered double hydroxides-supported nano noble metal catalysts
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.
Kantam, Mannepalli Lakshmi,Kumar, Karasala Vijaya,Sreedhar, Bojja
p. 959 - 964
(2007)
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Stereochemical Control in Microbial Reduction. XXI. Effect of Organic Solvents on Reduction of α-Keto Esters Mediated by Bakers' Yeast
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.
Nakamura, Kaoru,Kondo, Shin-ichi,Kawai, Yasushi,Ohno, Atsuyoshi
p. 2738 - 2743
(1993)
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REDUCTION BY BAKERS' YEAST IN BENZENE
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
Nakamura, Kaoru,Kondo, Shin-ichi,Kawai, Yasushi,Ohno, Atsuyoshi
p. 7075 - 7078
(1991)
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Enantioselective hydrogenation of ethyl pyruvate catalyzed by alumina support rhodium modified with quinine
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.
Xiong, Wei,Ma, Hongxia,Hong, Yanyi,Chen, Hua,Li, Xianjun
p. 1449 - 1452
(2005)
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Continuous platinum-catalyzed enantioselective hydrogenation in 'supercritical' solvents
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.
Wandeler,Kuenzle,Schneider,Mallat,Baiker
p. 673 - 674
(2001)
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Improvement of the enantioselectivity in the enantioselective hydrogenation of ethyl pyruvate by addition of achiral tertiary amines
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.
Margitfalvi, Jozsef L.,Talas, Emilia,Hegedus, Mihaly
p. 645 - 646
(1999)
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A new cinchona-modified platinum catalyst for the enantioselective hydrogenation of pyruvate: The structure of the 1:1 alkaloid-reactant complex
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.
Bartok, Mihaly,Felfoeldi, Karoly,Toeroek, Bela,Bartok, Tibor
p. 2605 - 2606
(1998)
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Enantioselective hydrogenation of ethyl pyruvate catalyzed by α- and β-isocinchonine-modified Pt/Al2O3 in acetic acid
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.
Bartok, Mihaly,Sutyinszki, Maria,Felfoeldi, Karoly
p. 207 - 214
(2003)
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Asymmetric hydrogenation on platinum: Nonlinear effect of coadsorbed cinchona alkaloids on enantiodifferentiation
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.
Huck,Buergi,Mallat,Baiker
p. 276 - 287
(2003)
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Mesoporous silica-supported Pt catalysts in enantioselective hydrogenation of ethyl pyruvate
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.
Chung, Iljun,Kim, Jeongmyeong,Song, Byeongju,Yun, Yongju
(2020)
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Enantioselective hydrogenation of α-keto esters over cinchona-Pt/Al2O'3 catalyst. Kinetic evidence for the substrate-modifier interaction in the liquid phase
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.
Margitfalvi,Hegedus,Tfirst
p. 571 - 580
(1996)
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Enantiopure (9-anthryl)(2-piperidyl)- and (9-anthryl)(2-pyridyl)methanols - Their use as chiral modifiers for heterogeneous hydrogenation of keto esters over Pt/Al2O3
A route toward the synthesis of the erythro isomer of (9-anthryl)(2- piperidyl)methanol is presented as well as resolution and assignment of the structure (through NMR). The use of both the erythro and threo enantiopure isomers of this new amino alcohol, and its precursor [(9-anthryl)(2-pyridyl) methanol], as chiral modifiers for the Pt/Al2O3 hydrogenation of ethyl lactate showed that the erythro isomer is not necessarily the most efficient chiral modifier. This is probably because of the 9-anthryl group. The enantioselectivities that this compound provides are not, as one would expect, higher than those observed with the naphthyl group. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Solladie-Cavallo, Arlette,Marsol, Claire,Azyat, Khalid,Roje, Marin,Welch, Christopher,Chilenski, Jennifer,Taillasson, Philippe,D'Orchymont, Hugues
p. 826 - 830
(2007)
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Solvothermal Alcoholysis Routes for Recycling Polylactide Waste as Lactic Acid Esters
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.
Petrus, Rafal,Bykowski, Dominik,Sobota, Piotr
p. 5222 - 5235
(2016)
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Mechanistic study for stereochemical control of microbial reduction of α-keto esters in an organic solvent
To elucidate the mechanism for stereochemical control of yeast reduction of α-keto esters in organic media, seven enzymes responsible for the reduction have been isolated from bakers' yeast and kinetic parameters for enzymatic reductions have been measured. In yeast reduction of ethyl 3-methyl-2-oxobutanoate (1f), enantiomeric excess in the produced (R)-hydroxy ester increases when an organic solvent is used as the reaction medium in place of water. Difference in K(m) of the enzymes contributes largely to the stereochemistry of reduction by whole yeast cell. Four enzymes contribute to catalytic reduction of 1f. K(m) of the (R)-producing enzyme has been found to be the lowest among those of four enzymes. Stereochemical course of the reduction shifts toward the (R)-product by lowering the substrate concentrations, because the (R)-producing enzyme is most active among the enzymes under diluted conditions. In yeast reduction of ethyl 2-oxohexanoate (1d), the corresponding (S)-hydroxy ester is obtained in water, whereas the antipode is given in benzene. Five enzymes participate to the reduction of 1d and the (R)-producing enzymes have smaller K(m)s than those of the (S)-producing enzymes. When the reaction is run in benzene, however, the produced α-hydroxy ester does not undergo further decomposition. The inhibition of enzymatic decomposition in an organic solvent is also accounted for by low concentration of α-hydroxy ester in aqueous phase surrounding the bakers' yeast.
Nakamura, Kaoru,Kondo, Shin-Ichi,Nakajima, Nobuyoshi,Ohno, Atsuyoshi
p. 687 - 694
(1995)
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Remarkable particle size effect in Rh-catalyzed enantioselective hydrogenations
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.
Hoxha, Fatos,van Vegten, Niels,Urakawa, Atsushi,Krumeich, Frank,Mallat, Tamas,Baiker, Alfons
p. 224 - 231
(2009)
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Non-Linear Effect of Modifier Composition on Enantioselectivity in Asymmetric Hydrogenation over Platinum Metals
Prominent non-linear behavior was observed when mixtures of cinchona alkaloids were applied as chiral modifiers in enantioselective hydrogenations over Pt/Al2O3 and Pd/TiO2. The phenomenon is traced to differences in the strength and geometry of alkaloid adsorption on the metal surface. In ethyl pyruvate hydrogenation under close to ambient conditions the weaker adsorbing quinidine (QD) outperformed the generally preferred modifier cinchonidine (CD) and afforded the highest ee (96-98%) at 1-5 bar. In the partial hydrogenation of 4-methoxy-6-methyl-2-pyrone to the dihydro derivative 4 CD gave 73% ee to (S)-4 and QD provided 72% ee to (R)-4, and still the alkaloid mixture containing less than 5 mol % CD afforded 15% ee to (S)-4. This nonlinear behavior may be advantageous in asymmetric synthesis as low purity chiral compounds can be applied as efficient modifiers for Pt or Pd.
Huck, Wolf-Rüdiger,Mallat, Tamas,Baiker, Alfons
p. 255 - 260
(2003)
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1-Naphthyl-1,2-ethanediol as a new chiral modifier of platinum in the enantioselective hydrogenation of activated ketones
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.
Marinas, Alberto,Mallat, Tamas,Baiker, Alfons
p. 666 - 669
(2004)
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Enantioselective hydrogenation over cinchona-modified Pt: The special role of carboxylic acids
The influence of acetic acid (AcOH) and trifluoroacetic acid (TFA) on the hydrogenation of ethyl-4,4,4-trifluoroacetoacetate has been investigated by using Pt/ A1203 modified by cinchonidine and O-methylcinchonidine. We have shown that the sometimes dramatic changes in enantioselectivity and rate cannot simply be interpreted by protonation of the alkaloid modifier. We propose a new three-step reaction pathway, involving interaction of the carboxylic acid with the reactant and the chiral modifier. The mechanism is supported by IR spectroscopic identification of cyclic TFA-modifier ion pairs. This new approach can rationalise the poorly understood role of acids in the enantioselective hydrogenation of activated ketones over cinchona-modified platinum metals.
Von Arx, Matthias,Buergi, Thomas,Mallat, Tamas,Baiker, Alfons
p. 1430 - 1437
(2002)
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Enantioselective heterogeneous catalysis. I. A working model for the catalyst:modifier:substrate interactions in chiral pyruvate hydrogenations
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.
Augustine,Tanielyan,Doyle
p. 1803 - 1827
(1993)
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Biotechnological properties of sponges from northeast Brazil: Cliona varians as a Biocatalyst for Enantioselective Reduction of Carbonyl Compounds
To research the potential ability of whole marine sponges to act as biocatalysts, this paper describes for the first time the employment of whole Cliona varians sponge in the stereoselective reduction of prochiral α-keto esters and isatin to the corresponding chiral alcohols. The addition of D-fructose, D-glucose or sucrose remarkably increased the conversion ratios and stereoselectivities by this marine sponge. Furthermore, in the presence of D-glucose and D-maltose, the reduction of isatin by C. varians afforded the corresponding 3-hydroxyindolin-2-one with high conversions (85-90percent) and good enantioselectivities (60-74percent). These results showed that the marine sponge presents great potential to be used as biocatalyst for stereoselective reduction of carbonyl compounds.
Riatto, Valéria B.,Victor, Mauricio M.,Sousa, Jaqueline F.,Menegola, Carla
p. 149 - 157
(2018/12/13)

Preparation method of (R)-(+)-2-p-hydroxyl phenoxyl propionic acid
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.
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(2018/11/22)

Synthesis of lactide from lactic acid and its esters in the presence of rare-earth compounds
A procedure is described for the synthesis of lactide by dehydration of L-lactic acid and subsequent depolymerization of its oligomer mixture in the presence of yttrium(III) and praseodymium(III) oxides, as well as of cerium(III) chloride heptahydrate. The catalytic activity of yttrium and praseodymium sesquioxides was determined at different temperatures at the oligomerization and deoligomerization stages. Ethyl lactate was prepared in the presence of Purolite C100 MB cation exchange resin and subjected to oligomerization followed by thermal decomposition of oligoester and oligolactic acid mixture in the presence of yttrium(III) and praseodymium(III) oxides and aqueous cerium(III) chloride.
Poryvaeva,Egiazaryan,Makarov,Moskalev,Razborov,Fedyushkin
p. 344 - 350
(2017/05/10)

13C MR Hyperpolarization of Lactate by Using ParaHydrogen and Metabolic Transformation in Vitro
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.
Cavallari, Eleonora,Carrera, Carla,Aime, Silvio,Reineri, Francesca
supporting information
p. 1200 - 1204
(2017/02/05)

Asymmetric hydrogenation of α-ketoesters on the Pt(111) surface
This contribution aims to provide a brief account of the remarkable recent findings and advances in heterogeneous catalyst design based on facet rich Pt(111) on carbon materials. Platinum(111) hexagonal nanocrystals are prepared using Tween 20 as a facet directing agent via a simple, efficient and scalable thermolytic reduction process in air. These highly dispersed Pt(111) nanocrystals on carbon act as single site catalytic systems and exhibit exceptional activity (yield and ee ～99%) and recyclability for the asymmetric hydrogenation of α-ketoesters.
Sharma, Poonam,Sharma, Rakesh K.
supporting information
p. 9038 - 9041
(2016/11/11)

Acidic function ionic liquid and its preparation and use in the synthesis of ethyl lactate
The invention discloses acidic functionalized ionic liquid, preparation and an application in ethyl lactate synthesis thereof. The acidic functionalized ionic liquid has a structural formula as shown in formula (I), wherein X represents one of the following groups: a triethylamino group, a tripropylamino group, a tri-isopropylamino group, a tributylamino group, and a tri-isobutylamino group, and Y is HSO4. The acidic functionalized ionic liquid is applicable to ethyl lactate synthesis, and has the advantages of environment friendliness, high conversion rate and selectivity, and simple process.
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Paragraph 0038-0039

(2017/03/28)

Size-Dependent Enantioselective Adsorption of Racemic Molecules through Homochiral Metal-Organic Frameworks Embedding Helicity
Homochiral metal-organic frameworks (HMOFs) are efficient materials for enantioselective adsorption. However, the combination of size selectivity and enantioselectivity is still a major challenge in the field of HMOFs. Herein, two enantiomorphic HMOFs built from predesigned proline-derived ligands are presented. Both of them show multiple homochiral features: they contain four different helical chains and three types of helical channels. Due to the size effect of the helical channels, each HMOF can enantioselectively adsorb methyl lactate with high ee. The results reveal a new approach toward size-dependent enantioselective separation of racemic compounds by using HMOFs built from inexpensive proline derivatives.
Xu, Zhong-Xuan,Fu, Hong-Ru,Wu, Xin,Kang, Yao,Zhang, Jian
p. 10236 - 10240
(2015/07/07)

Conversion of lactides into ethyl lactates and value-added products
This Letter describes an attractive and efficient method for Mg(OR)2-mediated lactide alcoholysis. The catalysts were generated in situ from di-n-butylmagnesium and ROH to prevent aggregation of Mg(OR)2. The reaction of ROH [R = Me,
Bykowski, Dominik,Grala, Agnieszka,Sobota, Piotr
supporting information
p. 5286 - 5289
(2015/01/16)

RECOVERY METHOD OF HIGHLY PURE LACTIC ACID AND ALKYL LACTATE
A method for recovery of highly pure alkyl lactate and lactic acid is provided, which includes a step 1 for producing source liquid comprising lactic acid or ammonium lactate; a step 2 for dehydrating the source liquid product of step 1; a step 3 for producing liquid mixture by sequentially adding and stirring alcohol and acid solution to the dehydrated source liquid; a step 4 for separating and removing ammonium salt precipitation from the liquid mixture of step 3; a step 5 for producing alkyl lactate from ammonium salt-free liquid mixture by esterification reaction; and a step 6 for separating alcohol and alkyl lactate by distillation from the mixture of step 5.
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(2012/06/16)

New phenomenon in competitive hydrogenation of binary mixtures of activated ketones over unmodified and cinchonidine-modified Pt/alumina catalyst
Competitive hydrogenations of eight binary mixtures of ethyl pyruvate (EP), methyl benzoylformate (MBF), ketopantolactone (KPL), pyruvic aldehyde dimethyl acetal (PA) and trifluoroacetophenone (TFAP) on platinum/alumina catalysts unmodified (racemic hydrogenation) and modified by cinchonidine (chiral hydrogenation) were studied under the experimental conditions of the Orito reaction. Reaction rates of chiral and racemic hydrogenations were determined and relative adsorption coefficients were calculated. In the competitive chiral hydrogenation of EP + MBF, EP + TFAP and KPL + MBF binary mixtures a new phenomenon was observed: namely the EP and KPL are hydrogenated faster than MBF and TFAP, whereas in racemic one the MBF and TFAP are hydrogenated faster than EP or KPL. Effects of the activated ketones structure on their reactivity and the stability of the surface complexes are discussed. It was found that differences in rate enhancement are caused by the differences both in the adsorptivity and in the reactivity of adsorbed substrates and adsorbed intermediate complexes.
Balázsik, Katalin,Szori, Kornél,Szollosi, Gy?rgy,Bartók, Mihály
experimental part
p. 1410 - 1414
(2012/07/31)

Highly stereoselective reduction of prochiral ketones by a bacterial reductase coupled with cofactor regeneration
A carbonyl reductase gene (yueD) from Bacillus sp. ECU0013 was heterologously overexpressed in Escherichia coli, and the encoded protein (BYueD) was purified to homogeneity and characterized. The NADPH-dependent reductase showed a broad substrate spectrum towards different aromatic ketones, and α- and β-ketoesters. Although the enantioselectivity was high to moderate for the reduction of α-ketoesters, all the tested β-ketoesters and aromatic ketones were reduced to the corresponding chiral alcohols in enantiomerically pure forms. Furthermore, the practical applicability of this enzyme was evaluated for the reduction of ethyl 4-chloro-3-oxobutanoate (1a). Using Escherichia coli cells coexpressing BYueD and glucose dehydrogenase, 215 g L-1 (1.3 M) of 1a was stoichiometrically converted to ethyl (R)-4-chloro-3-hydroxybutanoate ((R)-1b) in an aqueous-toluene biphasic system by using a substrate fed-batch strategy, resulting in an overall hydroxyl product yield of 91.7% with enantiomeric purity of 99.6% ee.
Ni, Yan,Li, Chun-Xiu,Wang, Li-Juan,Zhang, Jie,Xu, Jian-He
experimental part
p. 5463 - 5468
(2011/09/12)

The chiral pool as valuable natural source: New chiral mesogens made from lactic acid
Twenty new enantiopure chiral materials have been synthesized, showing liquid crystalline phases of smectic (SmA*), twisted grain boundary (TGB) and cholesteric (N*) type. The central ester-linkage as well as the length of the attached alkyl-chains were varied in a systematic way and the effects of these structural changes on the liquid crystalline properties have been studied. The liquid crystalline phases were characterized by means of differential scanning calorimetry, polarisation microscopy as well as small angle X-ray diffraction (SAXS). Copyright Taylor & Francis Group, LLC.
Brombach,Neudoerfl,Blunk
scheme or table
p. 62 - 74
(2012/01/06)

The first case of competitive heterogeneously catalyzed hydrogenation using continuous-flow fixed-bed reactor system: Hydrogenation of binary mixtures of activated ketones on Pt-alumina and on Pt-alumina-cinchonidine catalysts
Under the experimental conditions of the Orito reaction the competitive hydrogenations of four binary mixtures of ethyl pyruvate (EP), methyl benzoylformate (MBF), pyruvic aldehyde dimethyl acetal (PA) and 2,2-diethoxyacetophenone (DAP) on unmodified Pt/Al2O3 (racemic hydrogenation) and catalyst modified by cinchonidine (chiral hydrogenation) were studied using continuous-flow fixed-bed reactor system (CFBR). Conversions of chiral and racemic hydrogenations were determined under 4 MPa H2 pressure, at 293 K using toluene/acetic acid 9/1 as solvent. In the competitive chiral hydrogenation of MBF + EP and DAP + PA binary mixtures (S1 + S2) a new phenomenon was observed: namely the EP and PA are hydrogenated faster than MBF and DAP, whereas in racemic one the MBF and DAP are hydrogenated faster than the former ketones. The phenomenon verified for the first time in CFBR is dependent on the adsorption mode of the surface complexes of various compositions (S1-Pt, S2-Pt, S1-CD-Pt, S2-CD-Pt, CD = cinchonidine). In the chiral hydrogenation of DAP a rate decrease, i.e., "ligand deceleration" was observed instead of rate enhancement. Graphical Abstract: [Figure not available: see fulltext.]
Sz?ll?si, Gyo?rgy,Makra, Zsolt,Fül?p, Ferenc,Bartók, Mihály
scheme or table
p. 1616 - 1620
(2012/03/08)

Synthesis and characterization of chiral mono N-heterocyclic carbene-substituted rhodium complexes and their catalytic properties in hydrosilylation reactions
Different chiral mono-substituted N-heterocyclic carbene complexes of rhodium were prepared, starting from [Rh(COD)Cl]2 (COD = cyclooctadiene) by addition of free N-heterocyclic carbenes (NHC), or an in-situ deprotonation of the corresponding iminium salt. All new complexes were characterized by spectroscopy methods. In addition, the structures of chloro(η4-1,5-cyclooctadiene)(1,3-di-[(1R,2R,3R,5S)-2,6, 6-trimethylbicyclo[3.1.1]hept-3-yl] imidazolin-2-ylidene)rhodium(I) (5a), chloro(η4-1,5-cyclooctadiene)(1,3-di-[(1R,2S,5R) -2-isopropyl-5-menthylcyclohex-1-yl]imidazol-2-ylidene)rhodium(I) (5b) and chloro(η4-1,5-cyclooctadiene)(1,3-di-[(2R,4S,5S) -2-methyl-4-phenyl-1,3-dioxacyclohex-5-yl]imidazolin-2-ylidene)rhodium(I) (5i) were analyzed by DFT-calculations. The enantioselective hydrosilylation of acetophenone, ethylpyruvate and n-propylpyruvate with diphenylsilane and hydrolysis was carried out with chiral C2-symmetrical mono-substituted N-heterocyclic carbene rhodium complexes giving for the first time an enantioselective excess of up to 74% ee in the case of the n-propylpyruvate.
Steinbeck, Martin,Frey, Guido D.,Schoeller, Wolfgang W.,Herrmann, Wolfgang A.
scheme or table
p. 3945 - 3954
(2011/12/22)

PROCESS INCLUDING HYDROGENOLYSIS OF BIOMASS FOLLOWED BY DEHYDROGENATION AND ALDOL CONDENSATION FOR PRODUCING ALKANES
A method comprises providing a bio-based feedstock; contacting the bio-based feedstock with a solvent in a hydrolysis reaction to form an intermediate stream comprising carbohydrates; contacting the intermediate stream with an aqueous phase reforming catalyst to form a plurality of oxygenated intermediates, wherein a first portion of the oxygenated intermediates are recycled to form the solvent; and contacting at least a second portion of the oxygenated intermediates with a condensation catalyst comprising a base functionality to form a fuel blend.
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Page/Page column 34-37

(2011/12/02)

Dynamic kinetic resolution of α-substituted β-ketoesters catalyzed by Baeyer-Villiger monooxygenases: Access to enantiopure α-hydroxy esters
BVMOs make a play: The dynamic kinetic resolution of racemic α-alkyl-β-ketoesters was performed through a selective Baeyer-Villiger oxidation employing different Baeyer-Villiger monooxygenases (BVMOs) in mild basic media. The product diesters were obtained with excellent yields and enantioselectivities, and used as precursors for optically active α-hydroxy esters.
Rioz-Martínez, Ana,Cuetos, Aníbal,Rodríguez, Cristina,De Gonzalo, Gonzalo,Lavandera, Iván,Fraaije, Marco W.,Gotor, Vicente
supporting information; experimental part
p. 8387 - 8390
(2011/10/09)

Chemoselective alcoholysis of lactide mediated by a magnesium catalyst: An efficient route to alkyl lactyllactate
Alkyl-(S,S)-O-lactyllactate was prepared by chemoselective alcoholysis of lactide LA mediated by a magnesium catalyst. When ROH reacted with LA it yielded the ring-opened product R-(S,S)-O-lactyllactate exclusively, which remained intact as long as LA was present in the reaction mixture. Consumption of LA caused the reaction to proceed further giving R-(S)-lactate.
Grala, Agnieszka,Ejfler, Jolanta,Jerzykiewicz, Lucjan B.,Sobota, Piotr
supporting information; scheme or table
p. 4042 - 4044
(2011/06/18)

PROCESS FOR PREPARATION OF PURE ALKYL ESTERS FROM ALKALI METAL SALT OF CARBOXYLIC ACID
The dehydrated alkali metal salts of carboxylic acid are dissolved in the alcohol such as methanol or ethanol or butanol to make their solution in corresponding alcohol. The solution alcohol is further treated with carbon dioxide under pressure or at atmospheric pressure at elevated temperature such as 150 to 200° C. The carboxylic acid gets converted into corresponding alkyl ester and calcium carbonate or sodium carbonate or potassium carbonate as the byproduct. Calcium lactate or Sodium lactate or Sodium acetate or Sodium benzoate or Sodium salicylate as alkali metal salt solution prepared in Methanol or Ethanol or Butanol when treated with carbon di-oxide under pressure or at atmospheric pressure at elevted temperature gets converted to Methyl lactate or Ethyl lactate or Methyl acetate or Methyl benzoate or Methyl salicylate as product.
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Page/Page column 17-18

(2011/04/14)

Enantioselective ketoester reductions in water: A comparison between microorganism-and ruthenium-catalyzed reactions
In the search for green chemistry methods for the enantioselective reduction of ketoesters Saccharomyces cerevisiae-and ruthenium-catalyzed reactions in water have been investigated. The highest enantiomeric excesses for the reduction of α-and β-ketoesters have been obtained by S. cerevisiae. Chiral ruthenium catalysts are active for the reduction of all ketoesters with low to moderate enantioselectivities depending on the nature of the substrate and ligand. Interestingly, for several substrates both enantiomers of the hydroxyesters have been obtained according either to the catalytic method or to the structure of the ligand.
Zeror, Saoussen,Collin, Jacqueline,Fiaud, Jean-Claude,Zouioueche, Louisa Aribi
experimental part
p. 1211 - 1215
(2010/10/20)

Enantioselective hydrogenation of ethyl pyruvate and 1-phenyl-1,2- propanedione on catalysts prepared by impregnation of colloidal platinum on SiO2
The enantioselective hydrogenation of ethyl pyruvate and 1-phenyl-1,2-propanedione was studied at 298 K and 40 bar of H2 over colloidal Pt stabilized with cinchonidine (CD) and supported on silica. The catalysts were prepared by impregnation of colloidal
Ruiz, Doris P.,Fierrob, Jose? L.G.,Reyes, Patricio A.
experimental part
p. 262 - 269
(2010/09/03)

NOBLE METAL CATALYSTS
Catalyst systems consisting of supported or unsupported transition metal catalysts which have modifiers on the surface. The modifiers have sulphur-containing functionalities (G0). In addition, the modifiers may have a spacer (Sp) and a Bronsted
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Page/Page column 8-9

(2010/05/13)

Ferrocenyl-aryl based trans-chelating diphosphine ligands: Synthesis, molecular structure and application in enantioselective hydrogenation
Potentially trans-chelating diphosphine ligands based on a ferrocenyl-aryl backbone were synthesised in a four-step sequence and the molecular structures in the solid state of two representatives were determined by X-ray diffraction. High throughput screening of these ligands in rhodium-, ruthenium- and iridium-mediated hydrogenations of a variety of alkenes and ketones revealed that these ligands can deliver high enantioselectivity for alkenes (up to 98% ee) but are less selective when ketones are used as the substrates. The coordination behaviour of one ligand in its square planar palladium and platinum dichloride complexes was studied by 31P NMR and only trans-chelated complexes, together with oligomeric by-products, were observed. Reaction with the (p-cymene)ruthenium dichloride dimer, [RuCl2(pcymene)] 2, resulted in a mixture of diastereomeric complexes.
Schuecker, Raffael,Mereiter, Kurt,Spindler, Felix,Weissensteiner, Walter
scheme or table
p. 1063 - 1074
(2010/06/17)

BIS(FERROCENYLPHOSPHINO) FERROCENE LIGANDS USED IN ASSYMETRIC HYDROGENATION REACTIONS
Abstract Compounds of the formula (I) in the form of racemates, enantiomerically pure diastereomers or a mixture of diastereomers, where the radicals R1 are identical or different and are each C1-C4-alkyl; m is 0 or an integer from 1 to 4; n is 0 or an integer from 1 to 3; p is 0 or an integer from 1 to 5; R2 is an aromatic hydrocarbon radical or a C-bonded heterohydrocarbon radical and R3 is an aliphatic or C-bonded heteroaliphatic hydrocarbon radical; R2 and R3 are identical or different and are each an aliphatic or C-bonded heteroaliphatic hydrocarbon radical; R4 is an unsubstituted or C1-C6-alkyl-, C1-C6-alkoxy- or halogen-substituted hydrocarbon radical; and A is a secondary amino group, are ligands for metal complexes which are suitable as catalysts for homogeneous enantioselective hydrogenation.
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Page/Page column 20-21

(2010/07/04)

Enantioselectivity of haloalkane dehalogenases and its modulation by surface loop engineering
In the loop: Engineering of the surface loop in haloalkane dehalogenases affects their enantiodiscrimination behavior. The temperature dependence of the enantioselectivity (lnE versus 1/T) of β-bromoalkanes by haloalkane dehalogenases is reversed (red data points) by deletion of the surface loop; the selectivity switches back when an additional single-point mutation is made. This behavior is not observed for -bromoesters.
Prokop, Zbynek,Sato, Yukari,Brezovsky, Jan,Mozga, Tomas,Chaloupkova, Radka,Koudelakova, Tana,Jerabek, Petr,Stepankova, Veronika,Natsume, Ryo,Van Leeuwen, Jan G. E.,Janssen, Dick B.,Florian, Jan,Nagata, Yuji,Senda, Toshiya,Damborsky, Jiri
supporting information; experimental part
p. 6111 - 6115
(2010/11/05)

Magnetically separable Pt catalyst for asymmetric hydrogenation
A magnetic Pt/SiO2/Fe3O4 catalyst consisting of chirally modified platinum supported on silica coated magnetite nanoparticles was prepared using an easy synthetic route and successfully applied for the enantioselective hydrogenation of various activated ketones. The magnetic catalyst modified with cinchonidine showed a catalytic performance (activity, enantioselectivity) in the asymmetric hydrogenation of various activated ketones in toluene comparable to the best known Pt/alumina catalyst used for these reactions. The novel catalyst can be easily separated from the reaction solution by applying an external magnetic field and recycled several times with almost complete retention of activity and enantioselectivity.
Panella, Barbara,Vargas, Angelo,Baiker, Alfons
scheme or table
p. 88 - 93
(2009/04/10)

Synthesis, coordination behaviour, structural features and use in asymmetric hydrogenations of bifep-type biferrocenes
A protocol for the synthesis of C2- and C1-symmetric 2,2″-diarylphosphino-substituted biferrocenes (bifep-type ligands) is presented and the preparation of four representatives is described [(S p,Sp)-2-R12P-2″- R 22P-1,1″-biferrocene; 1 (bifep): R1 = R2 = Ph; 2: R1 = Ph, R2 = Cy; 3: R1 = R2 = 3,5-Me2C6H3; 4: R1 = 3,5-Me2-4-OMe-C6H2, R2 = 3,5-(CF3)2C6H3]. In addition, the synthesis of three palladium(ii) complexes ([PdX2(L)], 10: L = 1, X = Cl; 11: L = 4, X = Cl; 12: L = 1, X = C6F5 and of four bifep ruthenium complexes (13: [RuCl(p-cymene)(1)]PF6; 14: [RuI(p-cymene)(1)]PF6; 15: [RuCl(benzene)(1)]PF6; 16: [RuI(p-cymene)(1)]I) is reported. In the solid state the biferrocene unit of complexes 10, 11 and 15 adopt either a (P)-shaped (10) or an (M)-shaped (11, 15) conformation. In solution, palladium complexes 10 and 11 are present as equilibrium mixtures of rapidly interconverting (P)- and (M)-shaped conformers. Rhodium- and iridium-mediated asymmetric hydrogenations of a number of olefins and one imine give products with only low to moderate enantiomeric excess, while in the ruthenium-catalyzed hydrogenation of ketones a maximum e.e. of 82% is obtained. The low enantioselectivities are assumed to be related to the conformational flexibility of bifep-type ligands.
Espino, Gustavo,Xiao, Li,Puchberger, Michael,Mereiter, Kurt,Spindler, Felix,Manzano, Blanca R.,Jalon, Felix A.,Weissensteiner, Walter
experimental part
p. 2751 - 2763
(2009/06/28)

Stereoselective reduction of carbonyl compounds with actinomycete: Purification and characterization of three α-keto ester reductases from Streptomyces avermitilis
We achieved the purification of three α-keto ester reductases (Streptomyces avermitilis keto ester reductase, SAKERs-I, -II, and -III) from Streptomyces avermitilis NBRC14893 whole cells. The molecular masses of the native SAKERs-I, -II, and -III were estimated to be 72, 38, and 36 kDa, respectively, by gel filtration chromatography. The subunit molecular masses of SAKERs-I, -II, and -III were also estimated to be 32, 32, and 34 kDa, respectively, by SDS-polyacrylamide gel electrophoresis. The purified SAKERs-II and -III showed a reducing activity for α-keto esters (in particular, for ethyl pyruvate). SAKER-I showed a high reducing activity not only toward the α- and β-keto esters, but also toward α-keto acid. The N-terminal region amino acid sequences of SAKERs-I, -II, and -III were identical to that of a putative oxidoreductase, SAV2750, a putative oxidoreductase, SAV1849, and a putative oxidoreductase, SAV4117, respectively, hypothetical proteins coded on the S. avermitilis genome.
Ishihara, Kohji,Kato, Chiaki,Yamaguchi, Hitomi,Iwai, Rieko,Yoshida, Momoko,Ikeda, Natsumi,Hamada, Hiroki,Masuoka, Noriyoshi,Nakajima, Nobuyoshi
body text
p. 3249 - 3257
(2009/04/10)

Asymmetric reduction of substituted α- and β-ketoesters by Bacillus pumilus Phe-C3
The enantioselective reduction of substituted α- and β-ketoesters using resting cells of Bacillus pumilus Phe-C3 was investigated. Effects of substrate concentration on the catalytic efficiency of the microorganism were studied. Preparative scale productions were carried out under the optimized conditions with 62.4-91.0% yields and 90.2-97.1% ee. The cells retained 80% of initial activity after recycling for six times.
He, Chunmao,Chang, Dongliang,Zhang, Jie
p. 1347 - 1351
(2008/12/20)

Facile alcoholysis of l-lactide catalysed by Group 1 and 2 metal complexes
The application of simple metal amides MN(SiMe3)2 as effective catalysts for the alcoholysis of cyclic esters are demonstrated. Excess dry methanol and L-lactide were added to a Schlenk flask at room temperature (RT) 1 mol% of MN(SiMe3)2, where M = Li, Na or K was added. A blank test was also performed where no catalyst was added giving no reaction. The conversion of M = Li, 45% to methyl (S,S)-lactyllactatewas obtained in 10 minutes at room temperature. Similar behaviors were observed for m = Na and K, where the reactions decelerated after 20 and 30 minutes. The application also extended to other cyclic esters such as capralactone where the ring-opening product was obtained rapidly in quantitative yield.
Phomphrai, Khamphee,Pracha, Supathana,Phonjanthuek, Phenphak,Pohmakotr, Manat
p. 3048 - 3050
(2008/09/21)

Identification of Candida tenuis xylose reductase as highly selective biocatalyst for the synthesis of aromatic α-hydroxy esters and improvement of its efficiency by protein engineering
Wild-type Candida tenuis xylose reductase and two Trp-23 mutants thereof catalyze NADH-dependent reduction of a homologous series of aromatic α-keto esters with absolute pseudo re-face stereoselectivity and broad tolerance for the substituent on the aromatic ring, producing the corresponding R-alcohols in high yield. The Royal Society of Chemistry.
Kratzer, Regina,Nidetzky, Bernd
p. 1047 - 1049
(2007/12/27)

Role of guiding groups in cinchona-modified platinum for controlling the sense of enantiodifferentiation in the hydrogenation of ketones
Systematic structural variations of cinchona-type modifiers used in the platinum-catalyzed hydrogenation of ketones give insight into the adsorption mode of the modifier and its interaction with the substrate on the platinum surface under truly in situ conditions. The performance of a new modifier, O-(2-pyridyl)-cinchonidine, is compared to that of O-phenyl-cinchonidine and cinchonidine (CD). In the hydrogenation of ethyl pyruvate, ketopantolactone, and 2-methoxyacetophenone, CD gives the (R)-alcohol in excess. Introduction of the bulky O-phenyl group favors the (S)-enantiomer, whereas upon replacement of the phenyl by a 2-pyridyl group the (R)-alcohol is again the major product. This finding is particularly striking, because the two ether groups have virtually identical van der Waals volumes. A catalytic study including the nonlinear behavior of modifier mixtures, and attenuated total reflection infrared spectroscopy of the solid-liquid interface in the presence of hydrogen, revealed the adsorption mode and strength of the modifiers on Pt. Theoretical calculations of the modifier-substrate interactions offered a feasible explanation for the different role of the bulky ether groups: repulsion by the phenoxy and attraction by the 2-pyridoxy groups. Simulation of the interaction of o-pyridoxy-CD with ketopantolactone on a model Pt surface suggests that formation of two N-H-O-type H-bonds-involving the quinuclidine and pyridine N atoms, and the two keto-carbonyls in the substrate-controls the adsorption of the substrate during hydrogen uptake. This mechanistic study demonstrates the potential of insertion of suitable substituents into CD and their influence on adsorption and stereocontrol on the platinum surface.
Hoxha, Fatos,Koenigsmann, Lucia,Vargas, Angelo,Ferri, Davide,Mallat, Tamas,Baiker, Alfons
p. 10582 - 10590
(2008/02/13)

Catalytic asymmetric hydrogenation of α-ketoesters and quinoline using electronically enriched BINAP
Electronically enriched chiral BINAP derivatives were synthesized incorporating electron-donating substituents at the para-phenyl position and evaluated for the Ru-catalyzed homogeneous asymmetric hydrogenation of α-ketoesters with up to 92% ee. These diphophosphines were also excellent ligands for the iridium-catalyzed asymmetric hydrogenation of quinolines.
Jahjah, Mohamad,Alame, Mohamad,Pellet-Rostaing, Stephane,Lemaire, Marc
p. 2305 - 2312
(2008/03/12)

Asymmetric reduction of ketones using recombinant E. coli cells that produce a versatile carbonyl reductase with high enantioselectivity and broad substrate specificity
The gene encoding a versatile biocatalyst that shows high enantioselectivity for a variety of ketones, SCR (Saccharomyces cerevisiae carbonyl reductase), has been identified, cloned, and expressed in Escherichia coli. Two types of expression systems with high NADPH-regenerating capacities have been constructed. One is the tandem system, where the genes encoding SCR and GDH (glucose dehydrogenase) are located in the same plasmid, and the other is the two-plasmid system, where each of the SCR and GDH genes is located in separate plasmids that can coexist in one E. coli cell. Asymmetric reduction of ketones with the recombinant E. coli cells gave synthetically useful 20 alcohols, 11 of which were enantiomerically pure. The productivity of one of these products was as high as 41 g/L.
Ema, Tadashi,Yagasaki, Hideo,Okita, Nobuyasu,Takeda, Masahiro,Sakai, Takashi
p. 6143 - 6149
(2007/10/03)

Steric and electronic effects in the enantioselective hydrogenation of activated ketones on platinum: Directing effect of ester group
Steric effects in the Pt-catalyzed asymmetric hydrogenation of nine different α-ketoesters were studied by variation of the bulkiness at the keto and ester side of the substrates, and by using cinchonidine (CD), its 6′-methoxy derivative quinine, and o-ph
Diezi, Simon,Reimann, Sven,Bonalumi,Mallat, Tamas,Baiker, Alfons
p. 255 - 262
(2007/10/03)

Stereoselective reduction of carbonyl compounds using the cell-free extract of the earthworm, Lumbricus rubellus, as a novel source of biocatalyst
We found the reducing activity toward carbonyl compounds in the cell-free extract of the earthworm, Lumbricus rubellus. The earthworm extract had a reducing activity for keto esters in the presence of NADH or NADPH as a coenzyme. The earthworm extract red
Ishihara, Kohji,Nakajima, Nobuyoshi
p. 3077 - 3080
(2007/10/03)

TETRADENTATE FERROCENE LIGANDS AND THEIR USE
Compounds of the formula (I) in the form of racemates, mixtures of diastereomers or pure diastereomers, where RO and Roo are each, independently of one another, hydrogen, C1-C20-alkyl, C3-C8-cycloalkyl, C6-C14-aryl or C3-C12-heteroaryl having heteroatoms selected from the group consisting of O, S and N, which are unsubstituted or substituted by C1-C6-alkyl, C1-C6-alkoxy, C5-C8-cyclo-alkyl, C5-C8-cycloalkoxy, phenyl, C1-C6-alkylphenyl, C1-C6-alkoxyphenyl, C3-C8-heteroaryl, F or trifluoromethyl; the radicals R1 are each, independently of one another, a hydrogen atom, a halogen atom or a substituent bound to the cyclopentadienyl rings via a C atom, S atom, Si atom, a P(O) or P(S) group; R2 and R02 are each, independently of one another, a hydrogen atom, C1-C20-alkyl, C3-C8-cycloalkyl, C6-C14-aryl or C3-C12-heteroaryl having heteroatoms selected from the group consisting of O, S and N, which are unsubstituted or substituted by C1-C6-alkyl, C1-C6--alkoxy, C5-C8-cycloalkyl, C5-C8-cycloalkoxy, phenyl, C1-C6-alkylphenyl, C1-C6-alkoxyphenyl, C3-C8-heteroaryl, F or trifluoromethyl; the two indices m are each, independently of one another, 1, 2 or 3; n is 0 or 1; X1 is a secondary phosphine group or a cyclic phosphonite group, and X2 and X3 are each, independently of one another, a secondary phosphine group. The compounds of the formula (I) are valuable ligands for enantioselective catalysts for the hydrogenation of prochiral, unsaturated compounds.
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Page/Page column 31-34

(2010/02/15)

tert-butyl ethers: Renaissance of an alcohol protecting group. Facile cleavage with cerium(III) chloride/sodium iodide
The tert-butoxy derivative is one of the most underused alcohol protecting groups. After having developed an easy and useful protocol for its introduction, we offer here a simple procedure for its removal by treatment with anhydrous CeCl3 and NaI in CH3CN. The procedure led to the successful cleavage of aliphatic and aromatic tert-butyl ethers and was compatible with various other functionalities and protecting groups present in the molecule.
Bartoli, Giuseppe,Bosco, Marcella,Carlone, Armando,Locatelli, Manuela,Marcantoni, Enrico,Melchiorre, Paolo,Sambri, Letizia
p. 905 - 910
(2007/10/03)

A new class of versatile chiral-bridged atropisomeric diphosphine ligands: Remarkably efficient ligand syntheses and their applications in highly enantioselective hydrogenation reactions
A series of chiral diphosphine ligands denoted as PQ-Phos was prepared by atropdiastereoselective Ullmann coupling and ring-closure reactions. The Ullmann coupling reaction of the biaryl diphosphine dioxides is featured by highly efficient central-to-axial chirality transfer with diastereomeric excess >99%. This substrate-directed diastereomeric biaryl coupling reaction is unprecedented for the preparation of chiral diphosphine dioxides, and our method precludes the tedious resolution procedures usually required for preparing enantiomerically pure diphosphine ligands. The effect of chiral recognition was also revealed in a relevant asymmetric ring-closure reaction. The chiral tether bridging the two aryl units creates a conformationally rigid scaffold essential for enantiofacial differentiation; fine-tuning of the ligand scaffold (e.g., dihedral angles) can be achieved by varying the chain length of the chiral tether. The enantiomerically pure Ru- and Ir-PQ-Phos complexes have been prepared and applied to the catalytic enantioselective hydrogenations of α- and β-ketoesters (C=O bond reduction), 2-(6′-methoxy- 2′-naphthyl)-propenoic acid, alkyl-substituted β-dehydroamino acids (C=C bond reduction), and N-heteroaromatic compounds (C=N bond reduction). An excellent level of enantioselection (up to 99.9% ee) has been attained for the catalytic reactions. In addition, the significant ligand dihedral angle effects on the Ir-catalyzed asymmetric hydrogenation of N-heteroaromatic compounds were also revealed.
Qiu, Liqin,Kwong, Fuk Yee,Wu, Jing,Lam, Wai Har,Chan, Shusun,Yu, Wing-Yiu,Li, Yue-Ming,Guo, Rongwei,Zhou, Zhongyuan,Chan, Albert S. C.
p. 5955 - 5965
(2007/10/03)

Asymmetric reduction of a variety of ketones with a recombinant carbonyl reductase: Identification of the gene encoding a versatile biocatalyst
The gene encoding a versatile biocatalyst that shows high enantioselectivity for a variety of ketones, SCR (Saccharomyces cerevisiae carbonyl reductase), has been identified, cloned, and expressed in E. coli. Recombinant E. coli co-producing SCR and GDH (glucose dehydrogenase) is an easy-to-use, synthetically useful biocatalyst, and 8 out of the 16 alcohols obtained had enantiomeric purities of >98% ee.
Ema, Tadashi,Yagasaki, Hideo,Okita, Nobuyasu,Nishikawa, Kumiko,Korenaga, Toshinobu,Sakai, Takashi
p. 1075 - 1078
(2007/10/03)

Synthetic modifiers for platinum in the enantioselective hydrogenation of ketopantolactone: A test for the mechanistic models of ketone hydrogenation
Various derivatives of (R)-1-(1-naphthyl)-ethylamine have been synthesized and tested as chiral modifiers of Pt/alumina in the enantioselective hydrogenation of ketopantolactone. The best modifiers (ee up to 79%) possess an ester function in the α-position to the amino group. The modifiers performed far better in AcOH than in toluene, indicating that protonation of the N atom is important in enantioselection. The striking non-linear behaviour of modifier mixtures with cinchonine indicates that the alkaloid adsorbs much stronger on Pt than the naphthylethylamine derivatives. Two mechanistic models are proposed for interpretation of the results, involving an N-H-O or N +-H-O bond between the amine-type modifier and the keto carbonyl O atom of ketopantolactone, in apolar and protic media, respectively. In both cases the H atom originates from the modifier and not from the substrate ("half-hydrogenated-state"). The higher ee achieved in acidic medium is attributed to the better proton donor ability of the protonated amine modifiers. The models are applicable also to the hydrogenation of ethyl pyruvate.
Orglmeister, Elisabeth,Mallat, Tamas,Baiker, Alfons
p. 78 - 86
(2007/10/03)

Synthesis and application of phosphinoferrocenylaminophosphine ligands for asymmetric catalysis
(Chemical Equation Presented) A new class of bidentate ligands utilizing a phosphine-aminophosphine structure has been prepared on a ferrocenylethyl backbone in a straightforward and scalable fashion from acetylferrocene. The unique property of the α-ferrocenyl carbonium ion that allows the replacement of a variety of "leaving groups" with retention of configuration greatly facilitates the synthesis, and a number of ligands have been prepared by varying the nitrogen and phosphorus substituents on the aminophosphine. These readily prepared phosphinoferrocenylaminophosphines, known as BoPhoz ligands, show surprising hydrolytic and air stability, with no degradation after 3 years open to the air. The rhodium complexes of these ligands show exceedingly high enantioselectivities (generally > 95% ee) and activities often in excess of 50 000 catalyst turnovers per hour for the asymmetric hydrogenation of a wide variety of dehydro-α-amino acid and itaconic acid derivatives. They also show high activity and good to excellent enantioselectivity for the hydrogenation of a number of α-ketoesters.
Boaz, Neil W.,Mackenzie, Elaine B.,Debenham, Sheryl D.,Large, Shannon E.,Ponasik Jr., James A.
p. 1872 - 1880
(2007/10/03)

Tunable dendritic ligands of chiral 1,2-diamine and their application in asymmetric transfer hydrogenation
Tunable dendritic N-mono-sulfonyl ligands have been designed and synthesized via direct N-mono-sulfonylization of the chiral dendritic vicinal diamines and their ruthenium complexes demonstrated high catalytic and recyclable activities with comparable enantioselectivities to Noyori-Ikariya's TsDPEN-Ru in the asymmetric transfer hydrogenation of an extended range of substrates, such as ketones, keto esters, and olefins.
Liu, Weiguo,Cui, Xin,Cun, Linfeng,Zhu, Jin,Deng, Jingen
p. 2525 - 2530
(2007/10/03)

Synthesis of chiral catalyst modifiers by hydrosilylation of cinchonidine and their application in the hydrogenation of 1-phenylpropane-1,2-dione and ethyl pyruvate on a supported Pt/Al2O3 catalyst
Four new chiral modifiers were synthesized in order to investigate the effect of distal modifier substitution in the hydrogenation of ethyl pyruvate and 1-phenylpropane-1,2-dione on a supported Pt/Al2O3 catalyst. The chiral modifiers
Busygin, Igor,Toukoniitty, Esa,Sillanpaeae, Reijo,Murzin, Dmitry Yu.,Leino, Reko
p. 2811 - 2821
(2007/10/03)

Ru-catalyzed asymmetric hydrogenation of α-ketoesters with CeCl 3·7H2O as additive
(Chemical Equation Presented) An efficient asymmetric hydrogenation of α-ketoesters is reported with use of a catalyst prepared from [Ru((S)-3)(benzene)Cl]Cl and CeCl3-7H2O. α-Hydroxy esters are obtained in up to 96% ee. The addition of CeCl3· 7H2O not only improves the enantioselectivity, but also enhances the stability of the catalyst. As a result, the hydrogenation of methyl benzoylformate affords the product with 92% ee with a substrate/catalyst ratio of 10 000. Hydrolysis of 2 provides the final compound with 83% yield at 99% ee after a single recrystallization from 1,2-dichloroethylene.
Sun, Yanhui,Wan, Xiaobing,Wang, Jianping,Meng, Qinghua,Zhang, Hongwei,Jiang, Lijuan,Zhang, Zhaoguo
p. 5425 - 5427
(2007/10/03)