7699-00-5Relevant articles and documents
A Novel Aminoalcohol Modifier for the Enantioselective Hydrogenation of Ethyl Pyruvate on Pt/Alumina
Minder, B.,Mallat, T.,Baiker, A.,Wang, G.,Heinz, T.,Pfaltz, A.
, p. 371 - 378 (1995)
A novel chiral modifier, (R)-2-(1-pyrrolidinyl)-1-(1-naphthyl) ethanol (PNE), has been synthesised and tested in the enantioselective hydrogenation of ethyl pyruvate over Pt/alumina.An enantiomeric excess in (R)-ethyl lactate of up to 75percent was achieved.The influence of solvent, pressure, temperature, and concentrations of the components (reactant, modifier, catalyst) on the reaction rate and enantiodifferentiation was investigated.Among various polar and nonpolar solvents, acetic acid was found to be most suitable for reaching good enentioselectivity.Favorable reaction conditions are 1-10 bar hydrogen pressure, 0-25 deg C, and a catalyst loading 15 g liter-1.The efficiency of PNE is demonstrated by the very low modifier : reactant molar ratio (1 : 30,000) which is required to obtain maximum enantioselectivity.The performance and stability of the aminoalcohol-type modifier are compared to those of cinchona alkaloids.At low hydrogen pressure, the enantiodifferentiation of PNE is comparable to that of 10,11-dihydrocinchonidine.
Highly oxidized Pt species stabilized inside carbon nanotubes for asymmetric hydrogenation
Guan, Zaihong,Lu, Shengmei,Li, Can
, p. 1535 - 1542 (2015)
The chemical state and its influence on Pt species in or outside of the channels of CNTs and the effect on the asymmetric hydrogenation of α-ketoester were investigated. XPS analysis showed that 13% Pt species in a highly oxidized state (Pt4+) were stabilized inside the channels in the presence of Na+. There were more highly oxidized Pt species inside the CNTs than outside. The highly oxidized Pt species promoted the interaction between the nanoparticle and chiral modifier, which is crucial for high enantioselectivity. Hydrogen temperature programmed desorption showed that Pt nanoparticles confined in the channels can better activate hydrogen, which contributed to their high activity even at low hydrogen pressure.
Platinum nanoparticles supported on mesocellular silica foams as highly efficient catalysts for enantioselective hydrogenation
Kim, Jeongmyeong,Song, Byeongju,Hwang, Gyohyun,Bang, Yongju,Yun, Yongju
, p. 306 - 313 (2019)
Mesocellular silica foams (MCFs) with different pore size were synthesized and used as supports for Pt catalysts for enantioselective hydrogenation of ethyl pyruvate. The influences of the pore size of MCFs, the amount of Pt loading and H2 pressure on catalytic performance of cinchonidine-modified Pt/MCFs were investigated. Both activity and enantioselectivity of the Pt/MCF catalyst increased with the increase in the pore size. These results were attributed to the fact that the larger mesopores facilitate intraparticle diffusion of bulky chiral modifier molecules and generate more chirally modified Pt sites. The performances of Pt/MCFs were compared to those of Pt supported on non-porous silica (Pt/SiO2) and commercial Pt/Al2O3 catalysts. The 1 wt% Pt/MCFs showed superior performance than the 1 wt% Pt/SiO2 and the commercial 1 wt% Pt/Al2O3 catalysts. Furthermore, the 0.6 wt% Pt/MCF exhibited higher activity and enantioselectivity than the commercial 5 wt% Pt/Al2O3, one of the most efficient heterogeneous catalysts for this reaction, in spite of a considerably less Pt loading. At optimized reaction conditions, the Pt/MCF catalyst gave enantiomeric excess of 96% at 100% conversion. They also maintained high enantioselectivity during 10 successive reaction cycles, exhibiting high reusability.
Continuous Enantioselective hydrogenation of ethyl pyruvate in "Supercritical" ethan: Relation between phase behavior and catalytic performance
Baiker,Wandeler,Kuenzle,Schneider,Mallat
, p. 377 - 388 (2001)
Continuous hydrogenation of an α-ketoester was studied in a fixed-bed reactor over cinchonidine-modified Pt/Al2O3 using "supercritical" ethane as solvent. Ethane as solvent offers good enantioselectivity and very fast conversion of ethyl pyruvate to ethyl lactate. The phase behavior at 15°-50°C and 140 bar was studied in a computer controlled view cell. Elimination of the liquid-gas phase boundary in the reaction system at higher fluid density led to a significant enhancement of reaction rate only at low hydrogen concentrations. Changes in the composition of the reaction mixture with conversion had little effect on the phase behavior in the system ethane, ethyl lactate, ethyl pyruvate, and H2. The enantioselectivity dropped strongly in the experiments conducted at up to 140°C, while the reaction rate did not increase as expected from an Arrhenius-type behavior. The unambiguous interpretation of the striking changes in rate and selectivity of high-pressure reactions requires a careful analysis of the phase behavior under reaction conditions. The obvious limitations of describing multicomponent phase behavior with that of the pure solvent was shown in the results. The consideration of the phase behavior of a binary fluid system is an ideal guide for rationalizing the phase behavior-related phenomena typical of multicomponent high-pressure reaction systems.
Enhancing Effect of Residual Capping Agents in Heterogeneous Enantioselective Hydrogenation of α-keto Esters over Polymer-Capped Pt/Al2O3
Chung, Iljun,Song, Byeongju,Kim, Jeongmyeong,Yun, Yongju
, p. 31 - 42 (2021/01/11)
Heterogeneous enantioselective catalysis is considered a promising strategy for the large-scale production of enantiopure chemicals. In this work, polymer-capped Pt nanocatalysts having a uniform size were synthesized using poly(vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) and supported on γ-Al2O3. After a facile heat treatment process, their catalytic performance for enantioselective hydrogenation of α-keto esters, a structure-sensitive reaction, was investigated. The presence of residual capping agents on the Pt surface often perturbs the adsorption of reacting species and reduces performance in structure-sensitive reactions. However, the 1 wt % PVP-Pt/Al2O3 catalyst exhibited an enhancement in both activity and enantioselectivity compared to a reference Pt/Al2O3 catalyst prepared by wet impregnation. Under optimized reaction conditions, the cinchonidine-modified PVP-Pt/Al2O3 gave an enantiomeric excess of 95% for the enantioselective hydrogenation of methyl pyruvate despite the low Pt loading. We demonstrate that depending on the type of polymers, the residual capping agents can lead to site-selective blockage of the Pt surface, that is, defects or terraces. Quantitative and qualitative analyses also show that the noticeable improvement in enantioselectivity is attributed to the stable adsorption of chiral modifiers on selectively exposed Pt terrace sites. The findings of this work provide a promising strategy to prepare metal nanoparticles having selectively exposed sites and offer insights into the enhancing effect of residual capping agents on the catalytic properties in structure-sensitive reactions.
Efficient asymmetric synthesis of chiral alcohols using high 2-propanol tolerance alcohol dehydrogenase: Sm ADH2 via an environmentally friendly TBCR system
Yang, Zeyu,Fu, Hengwei,Ye, Wenjie,Xie, Youyu,Liu, Qinghai,Wang, Hualei,Wei, Dongzhi
, p. 70 - 78 (2020/01/21)
Alcohol dehydrogenases (ADHs) together with the economical substrate-coupled cofactor regeneration system play a pivotal role in the asymmetric synthesis of chiral alcohols; however, severe challenges concerning the poor tolerance of enzymes to 2-propanol and the adverse effects of the by-product, acetone, limit its applications, causing this strategy to lapse. Herein, a novel ADH gene smadh2 was identified from Stenotrophomonas maltophilia by traditional genome mining technology. The gene was cloned into Escherichia coli cells and then expressed to yield SmADH2. SmADH2 has a broad substrate spectrum and exhibits excellent tolerance and superb activity to 2-propanol even at 10.5 M (80%, v/v) concentration. Moreover, a new thermostatic bubble column reactor (TBCR) system is successfully designed to alleviate the inhibition of the by-product acetone by gas flow and continuously supplement 2-propanol. The organic waste can be simultaneously recovered for the purpose of green synthesis. In the sustainable system, structurally diverse chiral alcohols are synthesised at a high substrate loading (>150 g L-1) without adding external coenzymes. Among these, about 780 g L-1 (6 M) ethyl acetoacetate is completely converted into ethyl (R)-3-hydroxybutyrate in only 2.5 h with 99.9% ee and 7488 g L-1 d-1 space-time yield. Molecular dynamics simulation results shed light on the high catalytic activity toward the substrate. Therefore, the high 2-propanol tolerance SmADH2 with the TBCR system proves to be a potent biocatalytic strategy for the synthesis of chiral alcohols on an industrial scale.
Mesoporous silica-supported Pt catalysts in enantioselective hydrogenation of ethyl pyruvate
Chung, Iljun,Kim, Jeongmyeong,Song, Byeongju,Yun, Yongju
, (2020/06/28)
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.
Efficient Asymmetric Synthesis of Ethyl (S)-4-Chloro-3-hydroxybutyrate Using Alcohol Dehydrogenase SmADH31 with High Tolerance of Substrate and Product in a Monophasic Aqueous System
Chen, Rong,Liu, Qinghai,Wang, Hualei,Wei, Dongzhi,Xie, Youyu,Yang, Zeyu,Ye, Wenjie
, p. 1068 - 1076 (2020/07/06)
Bioreductions catalyzed by alcohol dehydrogenases (ADHs) play an important role in the synthesis of chiral alcohols. However, the synthesis of ethyl (S)-4-chloro-3-hydroxybutyrate [(S)-CHBE], an important drug intermediate, has significant challenges concerning high substrate or product inhibition toward ADHs, which complicates its production. Herein, we evaluated a novel ADH, SmADH31, obtained from the Stenotrophomonas maltophilia genome, which can tolerate extremely high concentrations (6 M) of both substrate and product. The coexpression of SmADH31 and glucose dehydrogenase from Bacillus subtilis in Escherichia coli meant that as much as 660 g L-1 (4.0 M) ethyl 4-chloroacetoacetate was completely converted into (S)-CHBE in a monophasic aqueous system with a >99.9% ee value and a high space-time yield (2664 g L-1 d-1). Molecular dynamics simulation shed light on the high activity and stereoselectivity of SmADH31. Moreover, five other optically pure chiral alcohols were synthesized at high concentrations (100-462 g L-1) as a result of the broad substrate spectrum of SmADH31. All these compounds act as important drug intermediates, demonstrating the industrial potential of SmADH31-mediated bioreductions.
Biotechnological properties of sponges from northeast Brazil: Cliona varians as a Biocatalyst for Enantioselective Reduction of Carbonyl Compounds
Riatto, Valéria B.,Victor, Mauricio M.,Sousa, Jaqueline F.,Menegola, Carla
, p. 149 - 157 (2018/12/13)
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.
A thermoregulated phase-separable chiral Pt nanocatalyst for recyclable asymmetric hydrogenation of α-ketoesters
Xue, Xiuru,Wang, Yanhua,Han, Fu-She
supporting information, p. 3346 - 3349 (2017/03/22)
The design and preparation of a chiral Pt nanocatalyst system possessing thermoregulated phase-separation property and its application in recyclable asymmetric hydrogenation of α-ketoesters are presented.
