3333-15-1Relevant academic research and scientific papers
Electrocatalytic asymmetric hydrogenation of α,β-unsaturated acids in a PEM reactor with cinchona-modified palladium catalysts
Atobe, Mahito,Fukazawa, Atsushi,Hashimoto, Yasushi,Sato, Yasushi,Tanaka, Kenta
, (2020/04/28)
We have developed an electrocatalytic asymmetric hydrogenation reaction using a proton-exchange membrane (PEM) reactor that employs a polymer electrolyte fuel cell and industrial electrolysis technologies. Reasonable enantioselectivities and excellent current efficiencies were obtained in the asymmetric hydrogenation of α-phenylcinnamic acid under mild conditions without adding a supporting electrolyte. The current density was crucial to achieving the improved results observed.
Kinetic analysis of enantioselective hydrogenation of 2,3-(E)-diarylpropenoic acids over a chiral cinchona alkaloid-modified Pd/C catalyst
Kim, Bokeun,Nakatsuji, Makoto,Mameda, Takuya,Kubota, Takeshi,Fujita, Morifumi,Sugimura, Takashi,Okamoto, Yasuaki
, p. 163 - 175 (2020/04/27)
Enantioselective hydrogenations of α,β-unsaturated carboxylic acids over cinchona alkaloid-modified Pd metal heterogeneous catalysts have received considerable attention because of scientific importance in molecular recognition catalysis as well as feasibility of industrial applications. In the present study, comprehensive kinetic analysis of the hydrogenation was conducted to disclose the crucial kinetic parameters controlling enantiodifferentiation and reaction rate with the combinations of four kinds of modifier and three kinds of substrate. Despite simplicity of the kinetic model, the present novel kinetic formulation allows us to describe the enantioselectivity as a function of modifier concentration, to estimate intrinsic enantioselectivity at the modified sites, to estimate respective reaction rates at the modified and unmodified sites, and to establish a correlation between the magnitude of ligand acceleration and kinetic parameters. The enantioselectivity is successfully correlated to the reaction rate. The adsorption strength of the modifier on Pd is suggested to decrease in the order, cinchonidine > cinchonine > quinine > quinidine. The roles played by benzylammine and the observed decrease in the selectivity at a high modifier concentration are also discussed. The kinetic model and formulation can be applied to analyze the catalytic behaviors and performance of Pt counterparts.
Kinetic analysis of the asymmetric hydrogenation of (: E)-2,3-diphenylpropenoic acid over cinchonidine derivative-modified Pd/C: Quinoline ring modification
Fujita, Morifumi,Nakatsuji, Makoto,Okamoto, Yasuaki,Sugimura, Takashi
, p. 6573 - 6582 (2020/11/13)
The effects of the quinoline ring modification of cinchonidine (CD) on the enantioselectivity of the asymmetric hydrogenation of (E)-2,3-diphenylpropenoic acid over chirally modified Pd/C were systematically analyzed from the kinetic points of view. The substitutions at the 2′- and/or 6′-positions of the quinoline ring of CD by a methyl, vinyl, n-butyl, or phenyl group decreased enantioselectivity over the whole range of the modifier concentration. Kinetic analysis allowed us to estimate the intrinsic enantioselectivity at modified sites and adsorption strength of the modifier. It is revealed that the substitutions reduce both the intrinsic enantioselectivity and adsorption strength of the parent modifier. The intrinsic enantioselectivity is correlated, most likely, to the modifier-substrate interaction strength. This journal is
Deracemizing α-Branched Carboxylic Acids by Catalytic Asymmetric Protonation of Bis-Silyl Ketene Acetals with Water or Methanol
Mandrelli, Francesca,Blond, Aurélie,James, Thomas,Kim, Hyejin,List, Benjamin
, p. 11479 - 11482 (2019/07/18)
We report a highly enantioselective catalytic protonation of bis-silyl ketene acetals. Our method delivers α-branched carboxylic acids, including nonsteroidal anti-inflammatory arylpropionic acids such as Ibuprofen, in high enantiomeric purity and high yields. The process can be incorporated in an overall deracemization of α-branched carboxylic acids, involving a double deprotonation and silylation followed by the catalytic asymmetric protonation.
Direct synthesis of in-situ chirally modified palladium nanocrystals without capping agents and their application in heterogeneous enantioselective hydrogenations
Gao, Xiuyun,Chen, Xueying,Li, Zhen Hua,He, Heyong
, p. 6100 - 6110 (2019/06/24)
Shape-controlled metal nanocrystals possess the advantages of specific atomic arrangement on the surface and uniform size, which can act as ideal model catalysts for heterogeneous enantioselective catalytic studies. Nevertheless, capping agents are commonly retained on the surface of the as-synthesized metal nanocrystals, which may hinder the necessary interaction between the substrate and the chiral modifiers coadsorbed on the metal surface for chiral recognition. In this paper, we directly synthesized dendritic or cubic palladium nanocrystals in-situ modified by chiral modifiers such as cinchonidine (CD) or S-proline through a one-pot strategy by replacing the conventional capping agents with the chiral modifiers. The as-prepared CD-modified Pd nanodendrite catalyst already exhibits enantioselectivity in the asymmetric hydrogenation of (E)-α-phenylcinnamic acid without subsequent chiral modification processes. The in-situ S-proline-modified Pd nanocube catalyst shows higher enantioselectivity than nanocubes synthesized with polyvinylpyrrolidone (PVP) or cetyltrimethylammonium bromide (CTAB) as traditional capping agents in asymmetric hydrogenation of acetophenone. Chiral modifiers have dual functions (both shape-control agents and catalytic functional molecules), which can not only eliminate the adverse effect of traditional capping agents (such as PVP) on heterogeneous enantioselective hydrogenations but also simplify the follow-up chiral modification step of metal catalysts, providing a simple and efficient synthetic protocol to directly prepare in-situ chirally modified metal nanocrystal catalysts.
Enantioselective hydrogenation of α-phenylcinnamic acids over cinchonidine-modified Pd/C commercial catalysts
Sato, Haruka,Mameda, Takuya,Nakai, Kengo,Misaki, Tomonori,Haruyama, Yuichi,Sonobe, Seiji,Kubota, Takeshi,Okamoto, Yasuaki,Sugimura, Takashi
, p. 31 - 45 (2016/02/20)
Enantioselective hydrogenation of α-phenylcinnamic acid (PCA) and p,p′-dimethoxyphenylcinnamic acid (DMPCA) was studied over a variety of commercial 5 % Pd/C catalysts to reveal catalyst properties suitable for obtaining high enantioselectivity. The catalysts were characterized by CO adsorption, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). It is confirmed that pretreatment at 353 K under atmospheric pressure of H2 before modification with cinchonidine is very effective for all the Pd/C catalysts used here to improve the selectivity and reaction rate. It is suggested that the distribution of Pd metal particles is crucial to attain high selectivity (ee% = 79 ± 1 for PCA, 89 ± 2 for DMPCA): a uniform or eggshell-type distribution of Pd is more suitable than an egg-white or egg-yolk-type distribution. It is also suggested that the dispersion of Pd metal particles controls the enantioselectivity over cinchonidine (CD)-modified Pd/C catalysts. XPS techniques are proposed to provide a convenient method to find desirable catalysts. The choice of such Pd/C catalysts could facilitate high-throughput guided study on highly enantioselective hydrogenation of α,β-unsaturated carboxylic acids.
EXAFS Characterization of Pd Catalysts for Enantioselective Hydrogenation of α-Phenylcinnamic Acid: Pretreatment Effects and Thiol Adsorption
Kubota, Takeshi,Sato, Haruka,Uchida, Takayuki,Kim, Tae Yeon,Omata, Koji,Misaki, Tomonori,Okamoto, Yasuaki,Sugimura, Takashi
, p. 2430 - 2440 (2016/11/25)
Abstract: The effects of the pretreatment and Pd-distribution on the enantioselective hydrogenation of α-phenylcinnamic acid over cinchonidine-modified Pd/C and Pd/Al2O3 were studied by use of EXAFS techniques combined with thiol ads
Adsorption and performance of chiral cinchona alkaloid modifiers over Pd/C catalyst for enantioselective hydrogenation of α-phenylcinnamic acids
Nakatsuji, Makoto,Misaki, Tomonori,Okamoto, Yasuaki,Sugimura, Takashi
, p. 1187 - 1191 (2016/11/02)
The enantioselective hydrogenation reactions of α-phenylcinnamic acid (PCA) and 4,4′-dimethoxy α-phenylcinnamic acid (DMPCA) were carried out over chiral cinchona alkaloidmodified Pd/C. Two sets of the modifiers were employed to get deeper insights into the effects of relative adsorption strength between the modifier and the substrate on the enantioselectivity; cinchonidine (CD)/cinchonine (CN) and quinine (QN)/quinidine (QD). The performances of the two sets of modifiers were compared by systematically varying the modifier concentration over a wide range. It was clearly substantiated that the origin of the low selectivity observed with QN/QD at an ordinary concentration is primarily due to its weak adsorption strength on Pd metal surface, which originates from the steric hindrance of the methoxy substituent at C6. A new modifier, 6-hydroxy CD, was found to exhibit a performance comparable to that of CD, implying that the steric hindrance of the 6-methoxy group of QN/QD is much more influential than the electronic effects.
Soluble polymer supported 2-imidazolidinone chiral auxiliary and method for manufacturing the same
-
Paragraph 0092; 0097-0101, (2017/01/02)
The present invention relates to a chiral auxiliary agent and a manufacturing method thereof and, more specifically, to a 2-imidazolidinone chiral auxiliary agent supported onto a polymer soluble in an organic solvent and a manufacturing method thereof. The chiral auxiliary agent in the present invention shows effects of being easy to separate reaction products and the chiral auxiliary agent after a termination of a reaction while fulfilling an economic efficacy of chiral auxiliary molecules by being supported onto the polymer soluble in the organic solvent.COPYRIGHT KIPO 2015
Systematic methodology for the development of biocatalytic hydrogen-borrowing cascades: Application to the synthesis of chiral α-substituted carboxylic acids from α-substituted α,β-unsaturated aldehydes
Knaus, Tanja,Mutti, Francesco G.,Humphreys, Luke D.,Turner, Nicholas J.,Scrutton, Nigel S.
, p. 223 - 233 (2015/02/19)
Ene-reductases (ERs) are flavin dependent enzymes that catalyze the asymmetric reduction of activated carbon-carbon double bonds. In particular, α,β-unsaturated carbonyl compounds (e.g. enals and enones) as well as nitroalkenes are rapidly reduced. Conversely, α,β-unsaturated esters are poorly accepted substrates whereas free carboxylic acids are not converted at all. The only exceptions are α,β-unsaturated diacids, diesters as well as esters bearing an electron-withdrawing group in α- or β-position. Here, we present an alternative approach that has a general applicability for directly obtaining diverse chiral α-substituted carboxylic acids. This approach combines two enzyme classes, namely ERs and aldehyde dehydrogenases (Ald-DHs), in a concurrent reductive-oxidative biocatalytic cascade. This strategy has several advantages as the starting material is an α-substituted α,β-unsaturated aldehyde, a class of compounds extremely reactive for the reduction of the alkene moiety. Furthermore no external hydride source from a sacrificial substrate (e.g. glucose, formate) is required since the hydride for the first reductive step is liberated in the second oxidative step. Such a process is defined as a hydrogen-borrowing cascade. This methodology has wide applicability as it was successfully applied to the synthesis of chiral substituted hydrocinnamic acids, aliphatic acids, heterocycles and even acetylated amino acids with elevated yield, chemo- and stereo-selectivity. A systematic methodology for optimizing the hydrogen-borrowing two-enzyme synthesis of α-chiral substituted carboxylic acids was developed. This systematic methodology has general applicability for the development of diverse hydrogen-borrowing processes that possess the highest atom efficiency and the lowest environmental impact. This journal is
