- Cobalt-catalyzed asymmetric hydrogenation of ketones: A remarkable additive effect on enantioselectivity
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A chiral cobalt pincer complex, when combined with an achiral electron-rich mono-phosphine ligand, catalyzes efficient asymmetric hydrogenation of a wide range of aryl ketones, affording chiral alcohols with high yields and moderate to excellent enantioselectivities (29 examples, up to 93% ee). Notably, the achiral mono-phosphine ligand shows a remarkable effect on the enantioselectivity of the reaction.
- Du, Tian,Wang, Biwen,Wang, Chao,Xiao, Jianliang,Tang, Weijun
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supporting information
p. 1241 - 1244
(2020/10/02)
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- Manganese catalyzed asymmetric transfer hydrogenation of ketones
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The asymmetric transfer hydrogenation (ATH) of a wide range of ketones catalyzed by manganese complex as well as chiral PxNy-type ligand under mild conditions was investigated. Using 2-propanol as hydrogen source, various ketones could be enantioselectively hydrogenated by combining cheap, readily available [MnBr(CO)5] with chiral, 22-membered macrocyclic ligand (R,R,R',R')-CyP2N4 (L5) with 2 mol% of catalyst loading, affording highly valuable chiral alcohols with up to 95% ee.
- Zhang, Guang-Ya,Ruan, Sun-Hong,Li, Yan-Yun,Gao, Jing-Xing
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supporting information
p. 1415 - 1418
(2020/11/20)
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- Ruthenium-catalyzed hydrogenation of aromatic ketones using chiral diamine and monodentate achiral phosphine ligands
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The Ru-catalyzed asymmetric hydrogenation of ketones with chiral diamine and monodentate achiral phosphine has been developed. A wide range of ketones were hydrogenated to afford the corresponding chiral secondary alcohols in good to excellent enantioselectivities (up to 98.1% ee). In addition, an appropriate mechanism for the asymmetric hydrogenation was proposed and verified by NMR spectroscopy.
- Wang, Mengna,Zhang, Ling,Sun, Hao,Chen, Qian,Jiang, Jian,Li, Linlin,Zhang, Lin,Li, Li,Li, Chun
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- C1-Symmetric PNP Ligands for Manganese-Catalyzed Enantioselective Hydrogenation of Ketones: Reaction Scope and Enantioinduction Model
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A family of ferrocene-based chiral PNP ligands is reported. These tridentate ligands were successfully applied in Mn-catalyzed asymmetric hydrogenation of ketones, giving high enantioselectivities (92%~99% ee for aryl alkyl ketones) as well as high efficiencies (TON up to 2000). In addition, dialkyl ketones could also be hydrogenated smoothly. Manganese intermediates that might be involved in the catalytic cycle were analyzed. DFT calculation was carried out to help understand the chiral induction model. The Mn/PNP catalyst could discriminate two groups with different steric properties by deformation of the phosphine moiety in the flexible 5-membered ring.
- Zeng, Liyao,Yang, Huaxin,Zhao, Menglong,Wen, Jialin,Tucker, James H. R.,Zhang, Xumu
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p. 13794 - 13799
(2020/11/30)
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- RETRACTED ARTICLE: The Manganese(I)-Catalyzed Asymmetric Transfer Hydrogenation of Ketones: Disclosing the Macrocylic Privilege
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The bis(carbonyl) manganese(I) complex [Mn(CO)2(1)]Br (2) with a chiral (NH)2P2 macrocyclic ligand (1) catalyzes the asymmetric transfer hydrogenation of polar double bonds with 2-propanol as the hydrogen source. Ketones (43 substrates) are reduced to alcohols in high yields (up to >99 %) and with excellent enantioselectivities (90–99 % ee). A stereochemical model based on attractive CH–π interactions is proposed.
- Passera, Alessandro,Mezzetti, Antonio
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supporting information
p. 187 - 191
(2019/12/11)
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- Efficient asymmetric synthesis of chiral alcohols using high 2-propanol tolerance alcohol dehydrogenase: Sm ADH2 via an environmentally friendly TBCR system
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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.
- Yang, Zeyu,Fu, Hengwei,Ye, Wenjie,Xie, Youyu,Liu, Qinghai,Wang, Hualei,Wei, Dongzhi
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- 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
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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.
- Chen, Rong,Liu, Qinghai,Wang, Hualei,Wei, Dongzhi,Xie, Youyu,Yang, Zeyu,Ye, Wenjie
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p. 1068 - 1076
(2020/07/06)
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- Iridium-Catalyzed Enantioselective Transfer Hydrogenation of Ketones Controlled by Alcohol Hydrogen-Bonding and sp3-C?H Noncovalent Interactions
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Iridium-catalyzed enantioselective transfer hydrogenation of ketones with formic acid was developed using a prolinol-phosphine chiral ligand. Cooperative action of the iridium atom and the ligand through alcohol-alkoxide interconversion is crucial to facilitate the transfer hydrogenation. Various ketones including alkyl aryl ketones, ketoesters, and an aryl heteroaryl ketone were competent substrates. An attractive feature of this catalysis is efficient discrimination between the alkyl and aryl substituents of the ketones, promoting hydrogenation with the identical sense of enantioselection regardless of steric demand of the alkyl substituent and thus resulting in a rare case of highly enantioselective transfer hydrogenation of tert-alkyl aryl ketones. Quantum chemical calculations revealed that the sp3-C?H/π interaction between an sp3-C?H bond of the prolinol-phosphine ligand and the aryl substituent of the ketone is crucial for the enantioselection in combination with O?H???O/sp3-C?H???O two-point hydrogen-bonding between the chiral ligand and carbonyl group. (Figure presented.).
- Murayama, Hiroaki,Heike, Yoshito,Higashida, Kosuke,Shimizu, Yohei,Yodsin, Nuttapon,Wongnongwa, Yutthana,Jungsuttiwong, Siriporn,Mori, Seiji,Sawamura, Masaya
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supporting information
p. 4655 - 4661
(2020/07/13)
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- A simple and efficient asymmetric hydrogenation of heteroaromatic ketones with iridium catalyst composed of chiral diamines and achiral phosphines
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An efficient iridium catalyst composed of a simple and commercially available o-methoxytriphenylphosphine and 9-Amino (9-deoxy) epi-cinchonine was applied to the asymmetric hydrogenation of heteroaromatic ketones. A range of simple heteroaromatic ketones could be hydrogenated with good to excellent enantioselectivities and high activities. In particular, thiophene ketones and furyl ketones furnished 98.6% ee with up to 2.18 × 104(1/h) TOF. This catalytic system can be of practical value.
- Li, Chun,Lu, Xunhua,Wang, Mengna,Zhang, Ling,Jiang, Jian,Yan, Shunfa,Yang, Yuanyong,Zhao, Yonglong,Zhang, Lin
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- Ruthenium(II)-Chitosan, an Enantioselective Catalyst for the Transfer Hydrogenation of N-Heterocyclic Ketones
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The present study aimed at extending the applicability of a recently developed stereoselective catalytic system to the preparation of optically enriched N-heterocyclic alcohols. Chiral ruthenium catalyst formed in situ using the chitosan biopolymer as ligand, which provided good results in the transfer hydrogenation of heterobicyclic compounds, such as 4-chromanone and 4-thiochromanone, was used in reactions of various N-containing prochiral ketones. High enantioselectivities were reached in transfer hydrogenations of bicyclic compounds bearing nitrogen either in aromatic or cycloaliphatic moieties, provided that the amino group was protected or shielded by a nearby substituent. Results were rationalized by interactions of the nitrogen with the metal and/or ligand. N-containing bicyclic compounds having heteroatoms in both rings were also prepared and tested. The detrimental effect of the pyridyl moiety was compensated by the beneficial influence of the heteroatom in the cycloaliphatic ring, as indicated by high rates and good enantioselectivities obtained in reactions of these compounds. Preparation of several N-heterocyclic alcohols, in good yields and high optical purities was achieved using Ru(II)-chitosan complex.
- Kolcsár, Vanessza Judit,Fül?p, Ferenc,Sz?ll?si, Gy?rgy
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p. 2725 - 2731
(2019/05/24)
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- Enhanced activity and modified substrate-favoritism of Burkholderia cepacia lipase by the treatment with a pyridinium alkyl-PEG sulfate ionic liquid
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Three types of pyridinium salts, i.e., 1-ethylpyridin-1-ium cetyl-PEG10 sulfate (PYET), 1-butylpyridin-1-ium cetyl-PEG10 sulfate (PYBU), and 1-(3-methoxypropyl)pyridin-1-ium cetyl-PEG10 sulfate (PYMP), have been prepared and evaluated for their activation property of Burkholderia cepacia lipase by comparison to the control IL-coated enzymes, 1-butyl-2,3-dimethylimidazolium cetyl-PEG10 sulfate-coated lipase PS (IL1-PS). Among the tested pyridinium salt-coated lipases, the PYET-coated lipase PS (PYET-PS) exhibited the best results; the transesterification of 1-(pyridin-2-yl)ethanol, 1-(pyridin-3-yl)ethanol, 1-(pyridin-4-yl)ethanol, or 4-phenylbut-3-en-2-ol proceeded faster than those of the IL1-PS-catalyzed reaction while maintaining an excellent enantioselectivity (E > 200). This improved efficiency was found to be dependent on the increased Kcat value.
- Kadotani, Shiho,Nokami, Toshiki,Itoh, Toshiyuki
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p. 441 - 447
(2019/01/04)
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- Hydroclassified Combinatorial Saturation Mutagenesis: Reshaping Substrate Binding Pockets of KpADH for Enantioselective Reduction of Bulky-Bulky Ketones
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A hydroclassified combinatorial saturation mutagenesis (HCSM) strategy was proposed for reshaping the substrate binding pocket by dividing 20 amino acids into four groups based on their hydrophobicity and size. These smart HCSM libraries could significantly reduce screening effort especially for the simultaneous mutagenesis of three or more residues and lacking high throughput screening methods. Employing HCSM strategy, the stereoselectivity of KpADH, an alcohol dehydrogenase from Kluyveromyces polysporus, was efficiently improved to 99.4% ee. (4-Chlorophenyl)(pyridin-2-yl)methanone (CPMK), generally regarded as a "hard-to-reduce" ketone, was used as a model substrate, and its corresponding chiral alcohol products could be utilized as antihistamine precursors. The best variant 50C10 displayed higher binding affinity and catalytic efficiency toward CPMK with KM/kcat of 59.3 s-1·mM-1, 3.51-fold that of KpADH. Based on MD simulations, increased difference between two binding pockets, enhanced hydrophobicity, and π-π and halogen-alkyl interactions were proposed to favor the enantioselective recognition and substrate binding in 50C10. Substrate spectrum analysis revealed that 50C10 exhibited improved enantioselectivity toward diaryl ketones especially with halo- or other electron-withdrawing groups. As much as 500 mM CPMK could be asymmetrically reduced into chiral diaryl alcohols with ee of 99.4% and a space-time yield of 194 g·L-1·d-1 without addition of external NADP+. This study provides an effective mutagenesis strategy for the protein engineering of substrate specificity and enantioselectivity.
- Xu, Guo-Chao,Wang, Yue,Tang, Ming-Hui,Zhou, Jie-Yu,Zhao, Jing,Han, Rui-Zhi,Ni, Ye
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p. 8336 - 8345
(2018/09/18)
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- Chiral tridentate phosphonic amine ligand and application thereof in asymmetric catalytic reaction
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The invention relates to a chiral tridentate phosphonic amine ligand and application thereof in an asymmetric catalytic reaction. The novel chiral tridentate phosphonic amine ligand disclosed by the invention is a first case of tridentate phosphonic amine ligand containing ferrocenyl chiral phosphine at present and is successfully applied to high-efficiency and high-selectivity asymmetric hydrogenation and similar reaction thereof for simple aromatic ketone and aliphatic ketone. The type of ligand has the advantages of simple synthetic route, low cost, easiness in large-scale synthesis and stable air; the chiral tridentate phosphonic amine ligand shows high activity and high selectivity for asymmetric hydrogenation reaction of carbon-oxygen double bond, and has a broad industrial application prospect.
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Paragraph 0080; 0081; 0082
(2017/08/29)
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- Iridium-Catalyzed Asymmetric Hydrogenation of Ketones with Accessible and Modular Ferrocene-Based Amino-phosphine Acid (f-Ampha) Ligands
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A series of tridentate ferrocene-based amino-phosphine acid (f-Ampha) ligands have been successfully developed. The f-Ampha ligands are extremely air stable and exhibited excellent performance in the Ir-catalyzed asymmetric hydrogenation of ketones (full conversions, up to >99% ee, and 500?000 TON). DFT calculations were performed to elucidate the reaction mechanism and the importance of the COOH group. Control experiments also revealed that the COOH group played a key role in this reaction.
- Yu, Jianfei,Long, Jiao,Yang, Yuhong,Wu, Weilong,Xue, Peng,Chung, Lung Wa,Dong, Xiu-Qin,Zhang, Xumu
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supporting information
p. 690 - 693
(2017/02/10)
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- Remarkably improved stability and enhanced activity of a: Burkholderia cepacia lipase by coating with a triazolium alkyl-PEG sulfate ionic liquid
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Three types of triazolium cetyl-PEG10 sulfate ionic liquid were synthesized and their activation of Burkholderia cepacia lipase was investigated; both the reaction rate and enantioselectivity depended on the cationic part of the coating ILs and 1-butyl-3-methyl-1,2,3-triazolium cetyl-PEG10 sulfate (Tz1)-coated lipase PS, which is especially suitable for the transesterification of 1-(pyridin-2-yl)ethanol, 1-(pyridin-3-yl)ethanol, and 1-(pyridin-4-yl)ethanol, among 12 types of tested secondary alcohol. The most important result was obtained when these enzymes were stored in an IL ([N221MEM][Tf2N]) solvent: Tz1-PS showed an amazing stability and it exhibited an excellent activity after 2 years when the enzyme was stored in [N221MEM][Tf2N].
- Nishihara,Shiomi,Kadotani,Nokami,Itoh
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supporting information
p. 5250 - 5256
(2017/11/09)
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- Third-Generation Amino Acid Furanoside-Based Ligands from d-Mannose for the Asymmetric Transfer Hydrogenation of Ketones: Catalysts with an Exceptionally Wide Substrate Scope
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A modular ligand library of α-amino acid hydroxyamides and thioamides was prepared from 10 different N-tert-butyloxycarbonyl-protected α-amino acids and three different amino alcohols derived from 2,3-O-isopropylidene-α-d-mannofuranoside. The ligand library was evaluated in the half-sandwich ruthenium- and rhodium-catalyzed asymmetric transfer hydrogenation of a wide array of ketone substrates, including simple as well as sterically demanding aryl alkyl ketones, aryl fluoroalkyl ketones, heteroaromatic alkyl ketones, aliphatic, conjugated and propargylic ketones. Under the optimized reaction conditions, secondary alcohols were obtained in high yields and in enantioselectivities up to >99%. The choice of ligand/catalyst allowed for the generation of both enantiomers of the secondary alcohols, where the ruthenium-hydroxyamide and the rhodium-thioamide catalysts act complementarily towards each other. The catalytic systems were also evaluated in the tandem isomerization/asymmetric transfer hydrogenation of racemic allylic alcohols to yield enantiomerically enriched saturated secondary alcohols in up to 98% ee. Furthermore, the catalytic tandem α-alkylation/asymmetric transfer hydrogenation of acetophenones and 3-acetylpyridine with primary alcohols as alkylating and reducing agents was studied. Secondary alcohols containing an elongated alkyl chain were obtained in up to 92% ee. (Figure presented.).
- Margalef, Jèssica,Slagbrand, Tove,Tinnis, Fredrik,Adolfsson, Hans,Diéguez, Montserrat,Pàmies, Oscar
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p. 4006 - 4018
(2016/12/30)
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- I86A/C295A mutant secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus has broadened substrate specificity for aryl ketones
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Thermoanaerobacter ethanolicus secondary alcohol dehydrogenase (SADH) reduces aliphatic ketones according to Prelog's Rule, with binding pockets for small and large substituents. It was shown previously that the I86A mutant SADH reduces acetophenone, which is not a substrate of wild-type SADH, to give the anti-Prelog R-product (Musa, M. M.; Lott, N.; Laivenieks, M.; Watanabe, L.; Vieille, C.; Phillips, R. S. ChemCatChem 2009, 1, 89–93.). However, I86A SADH did not reduce aryl ketones with substituents larger than fluorine. We have now expanded the small pocket of the active site of I86A SADH by mutation of Cys-295 to alanine to allow reaction of substituted acetophenones. As predicted, the double mutant I86A/C295A SADH has broadened substrate specificity for meta-substituted, but not para-substituted, acetophenones. However, the increase of the substrate specificity of I86A/C295A SADH is accompanied by a decrease in the kcat/Km values of acetophenones, possibly due to the substrates fitting loosely inside the more open active site. Nevertheless, I86A/C295A SADH gives high conversions and very high enantiomeric excess of the anti-Prelog R-alcohols from the tested substrates.
- Nealon, Christopher M.,Welsh, Travis P.,Kim, Chang Sup,Phillips, Robert S.
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p. 151 - 156
(2016/08/15)
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- Iron(II)/(NH)2P2 Macrocycles: Modular, Highly Enantioselective Transfer Hydrogenation Catalysts
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A generalized protocol for the synthesis of chiral (NH)2P2 macrocycles allows changing the linker between the phosphines and gives access to a family of such ligands, as demonstrated for the propane-1,3-diyl analogue. The corresponding complexes based on earth-abundant and nontoxic iron were applied as catalysts in the asymmetric transfer hydrogenation of polar double bonds. Thanks to the ligand modularity and to the use of tunable isonitriles as ancillary ligands, the catalyst system can be individually optimized for each substrate to give high enantioselectivity (up to 99.9% conversion and 99.6% ee, TOF up to >3950 h-1) for a broad scope of 26 substrates.
- Bigler, Raphael,Huber, Raffael,St?ckli, Marco,Mezzetti, Antonio
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p. 6455 - 6464
(2016/10/18)
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- A convenient enantioselective CBS-reduction of arylketones in flow-microreactor systems
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A convenient, versatile, and green CBS-asymmetric reduction of aryl and heteroaryl ketones has been developed by using the microreactor technology. The study demonstrates that it is possible to handle borane solution safely within microreactors and that the reaction performs well using 2-MeTHF as a greener solvent.
- De Angelis, Sonia,De Renzo, Maddalena,Carlucci, Claudia,Degennaro, Leonardo,Luisi, Renzo
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supporting information
p. 4304 - 4311
(2016/05/24)
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- Seawater-Based Biocatalytic Strategy: Stereoselective Reductions of Ketones with Marine Yeasts
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The large consumption of freshwater in fermentations and bio-transformations is a matter of concern for the sustainability of many bio-processes. The use of seawater to perform bio-processes is a sustainable alternative. In this work, we used marine yeasts from deep-sub-seafloor sediments grown in seawater as bio-catalysts to perform the stereoselective reduction of different ketones, and the bio-transformations were accomplished in seawater as well. Strains of Meyerozyma guilliermondii and Rhodotorula mucilaginosa were able to reduce different aromatic ketones with high molar conversions and moderate-to-high enantioselectivity with no significant differences between bio-catalysis performed in seawater and freshwater. Finally, the selected marine yeasts were used for the reduction of key intermediates in seawater for the synthesis of molecules of pharmaceutical interest (desogestrel, norgestrel, gestodene, pramipexole).
- Serra, Immacolata,Guidi, Benedetta,Burgaud, Gaetan,Contente, Martina L.,Ferraboschi, Patrizia,Pinto, Andrea,Compagno, Concetta,Molinari, Francesco,Romano, Diego
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p. 3254 - 3260
(2016/10/24)
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- NOVEL RUTHENIUM CATALYSTS AND THEIR USE FOR ASYMMETRIC REDUCTION OF KETONES
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Disclosed are novel ruthenium compounds of formula (Ia) and (Ib): wherein R1 and the moiety L ∩ L are defined herein. Also disclosed is a process for using these novel ruthenium compounds as catalysts for asymmetric hydrogenation and transfer hydrogenation of ketones with high reactivities and excellent selectivities.
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Page/Page column 22
(2015/01/16)
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- Efficient asymmetric transfer hydrogenation of ketones in ethanol with chiral iridium complexes of spiroPAP ligands as catalysts
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Highly efficient iridium catalyzed asymmetric transfer hydrogenation of simple ketones with ethanol as a hydrogen donor has been developed. By using chiral spiro iridium catalysts (S)-1a a series of alkyl aryl ketones were hydrogenated to chiral alcohols with up to 98% ee.
- Liu, Wei-Peng,Yuan, Ming-Lei,Yang, Xiao-Hui,Li, Ke,Xie, Jian-Hua,Zhou, Qi-Lin
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supporting information
p. 6123 - 6125
(2015/04/14)
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- Half-sandwich Ru(η6-C6H6) complexes with chiral aroylthioureas for enhanced asymmetric transfer hydrogenation of ketones-experimental and theoretical studies
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The reactions of [RuCl2(η6-C6H6)]2 with chiral aroylthiourea ligands yielded pseudo-octahedral half-sandwich "piano-stool" complexes. All the Ru(ii) complexes were characterized by analytical and spectral (UV-visible, FT-IR, 1H NMR and 13C NMR) studies. The molecular structures of the ligands (L2 and L4) and the complexes (2, 4 and 5) were confirmed by single crystal XRD. All the complexes were successfully screened as catalysts for the asymmetric transfer hydrogenation (ATH) of ketones using 2-propanol as the hydrogen source in the presence of KOH. The ATH reactions proceeded with excellent yields (up to 99%) and very good enantioselectivity (up to 99% ee). The scope of the present catalytic system was extended to substituted aromatic ketones and few hetero-aromatic ketones. Density functional theory (DFT) calculations predicted non-classical, concerted transition states for the ATH reactions. The catalytic activity of Ru-benzene complexes toward asymmetric reduction of ketones was significantly higher compared to that of p-cymene complex analogues. Such enhanced efficiency and product selectivity of Ru-benzene complexes compared to those of Ru-p-cymene complexes were rationalized by the computational study.
- Mary Sheeba, Mani,Preethi, Sankaranarayanan,Nijamudheen,Muthu Tamizh, Manoharan,Datta, Ayan,Farrugia, Louis J.,Karvembu, Ramasamy
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p. 4790 - 4799
(2015/10/05)
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- Chiral Cyclopentadienone iron complexes for the catalytic asymmetric hydrogenation of ketones
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Three chiral (cyclopentadienone)iron complexes derived from (R)-BINOL (CK1-3) were synthesized and their structures unambiguously confirmed by X-ray analysis (CK3). Under suitable conditions for the in situ conversion into the corresponding (hydroxycyclopentadienyl)iron hydrides (Me3NO, H2), the new chiral complexes were tested in the catalytic asymmetric hydrogenation of ketones, showing moderate to good enantioselectivity. In particular, the complex bearing methoxy substituents at the 3,3-positions of the binaphthyl moiety (CK2) proved remarkably more enantioselective than the unsubstituted one (CK1) and reached the highest level of enantioselectivity (up to 77% ee) ever obtained with chiral (cyclopentadienone)iron complexes. Reducto! Chiral (cyclopentadienone)iron complexes were synthesized and tested, after in situ activation, in the catalytic asymmetric hydrogenation of ketones leading to the highest enantiomeric excesses ever obtained with this type of catalysts.
- Gajewski, Piotr,Renom-Carrasco, Marc,Facchini, Sofia Vailati,Pignataro, Luca,Lefort, Laurent,De Vries, Johannes G.,Ferraccioli, Raffaella,Forni, Alessandra,Piarulli, Umberto,Gennari, Cesare
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supporting information
p. 1887 - 1893
(2015/03/18)
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- Synthesis of (R)-BINOL-Derived (Cyclopentadienone)iron Complexes and Their Application in the Catalytic Asymmetric Hydrogenation of Ketones
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A family of chiral (cyclopentadienone)iron complexes, featuring an (R)-BINOL-derived backbone, and their application in the asymmetric hydrogenation of ketones are described. The complexes differ from each other in the substituents at the 3,3′-positions of the binaphthyl residue (H, OH, OR, OCOR, OSO2R) or at the 2,5-positions of the cyclopentadienone ring [trimethylsilyl (TMS) or Ph]. Remarkably, eight precatalysts with different 3,3′-binaphthyl substitution [(R)-1c-1j] were synthesized from a common parent complex [(R)-1b] through direct functional group interconversion reactions of the complexes. The 3,3′-(bis)methoxy-substituted precatalyst (R)-1b gave the best catalytic performance, and its application scope was assessed in the hydrogenation of several ketones. The observed ee values (up to 77%) are much higher than those previously reported for other chiral (cyclopentadienone)iron complexes.
- Gajewski, Piotr,Renom-Carrasco, Marc,Facchini, Sofia Vailati,Pignataro, Luca,Lefort, Laurent,De Vries, Johannes G.,Ferraccioli, Raffaella,Piarulli, Umberto,Gennari, Cesare
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supporting information
p. 5526 - 5536
(2015/09/01)
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- Highly enantioselective transfer hydrogenation of ketones with chiral (NH)2P2 Macrocyclic Iron(II) complexes
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Bis(isonitrile) iron(II) complexes bearing a C2-symmetric diamino (NH)2P2 macrocyclic ligand efficiently catalyze the hydrogenation of polar bonds of a broad scope of substrates (ketones, enones, and imines) in high yield (up to 99.5 %), excellent enantioselectivity (up to 99 % ee), and with low catalyst loading (generally 0.1 mol %). The catalyst can be easily tuned by modifying the substituents of the isonitrile ligand. Paying the iron price: Bis(isonitrile) iron(II) complexes with a C2-symmetric diamino (NH)2P2 macrocyclic ligand efficiently catalyze the hydrogenation of polar bonds of a broad scope of substrates (ketones, enones, imines) in high yield (up to 99.5 %), excellent enantioselectivity (up to 99 % ee), and with low catalyst loading (generally 0.1 mol %).
- Bigler, Raphael,Huber, Raffael,Mezzetti, Antonio
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supporting information
p. 5171 - 5174
(2015/04/27)
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- Modular hydroxyamide and thioamide pyranoside-based ligand library from the sugar pool: New class of ligands for asymmetric transfer hydrogenation of ketones
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A large library of pyranoside-based hydroxyamide and thioamide ligands has been synthesized for asymmetric transfer hydrogenation in an attempt to expand the scope of the substrates to cover a broader range of challenging heteroaromatic and aryl/fluoroalkyl ketones. These ligands have the advantage that they are prepared from commercial D-glucose, D-glucosamine and α-amino acids, inexpensive natural chiral feedstocks. By carefully selecting the ligand components (substituents/configurations at the amide/thioamide moiety, the position of amide/thioamide group and the configuration at C-2), we found that pyranoside-based thioamide ligands provided excellent enantioselectivities (in the best cases, ees of >99% were achieved) in a broad range of ketones, including the less studied heteroaromatics and challenging aryl/fluoroalkyls. Note that both enantiomers of the reduction products can be obtained with excellent enantioselectivities by simply changing the absolute configuration of the thioamide substituent.
- Coll, Mercè,Pàmies, Oscar,Diéguez, Montserrat
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p. 2293 - 2302
(2014/07/21)
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- A solar light-driven, eco-friendly protocol for highly enantioselective synthesis of chiral alcohols via photocatalytic/biocatalytic cascades
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The judicious utilization of solar light for the asymmetric synthesis of optically active compounds by imitating natural photosynthesis introduces a new concept that harnesses this renewable energy in vitro for ultimate transformation into chiral chemical bonds. Herein, we present a comprehensive description of such a biomimetic endeavor towards the design and construction of an asymmetric artificial photosynthesis system that comprises an efficient method of nicotinamide cofactor (NADPH) regeneration under visible light employing a graphene-based light harvesting photocatalyst and its subsequent utilization in an enzyme-catalyzed asymmetric reduction of prochiral ketones to expediently furnish the corresponding chiral secondary alcohols. A detailed optimization study revealed a major dependency of the reaction outcome on the amount of cofactor, photocatalyst and enzyme used, as well as the mode of their addition. A series of structurally diverse ketones bearing an array of (hetero)aryl/alkyl substituents proved to be highly suitable to our photocatalytic-biocatalytic cascade approach, providing (R/S)-1-(hetero)aryl/ alkylethanols in excellent enantioselectivities (ee ~ 95->99.9%) under mild and environmentally benign conditions. To the best of our knowledge, the synthesis of these enantiopure alcohols employing a visible-light-driven nicotinamide cofactor regeneration strategy has been reported for the first time. Such enantioenriched alcohols act as versatile chiral building blocks for the synthesis of compounds having industrial and pharmaceutical relevance. In addition, this solar-to-chiral chemicals prototype appears advantageous from ecological and economical perspectives. We describe mechanistic pathways to demonstrate how the present catalytic synthesis protocol functions through perfect orchestration between visible-light-driven photocatalysis and biocatalysis to be successively applied in inducing asymmetry in an achiral molecule for the ultimate goal of solar energy utilization in the synthesis of valuable chiral fine chemicals. This work highlights the potential advantages of a bioinspired system to the pertinence of solar energy in asymmetric transformations leading to enantioenriched alcohol precursors, and thus opens up a new field of research that might emerge as an important breakthrough with promising implications towards generating a sustainable and non-fossil/non- nuclear energy future. the Partner Organisations 2014.
- Choudhury, Sumit,Baeg, Jin-Ook,Park, No-Joong,Yadav, Rajesh K.
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supporting information
p. 4389 - 4400
(2014/09/29)
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- Amine-tunable ruthenium catalysts for asymmetric reduction of ketones
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A series of efficient ruthenium catalysts has been developed for the asymmetric hydrogenation and transfer hydrogenation of ketones with high reactivities and selectivities. The new chiral bisdihydrobenzooxaphosphole (BIBOP)/diamineruthenium complexes catalyzed the enantioselective hydrogenation of substrates such as aryl and heteroaryl cyclic and alkyl ketones with substrate/catalyst (S/C) ratios of up to 100,000. The opposite sense of enantioselectivity can be obtained by proper selection of a diamine with a given chirality of the phosphine. The usefulness of the new system has been demonstrated in the asymmetric hydrogenation of a complex synthetic intermediate towards cholesteryl ester transfer protein (CETP) inhibitors at S/C 20,000 on large-scale operation.
- Rodriguez, Sonia,Qu, Bo,Fandrick, Keith R.,Buono, Frederic,Haddad, Nizar,Xu, Yibo,Herbage, Melissa A.,Zeng, Xingzhong,Ma, Shengli,Grinberg, Nelu,Lee, Heewon,Han, Zhengxu S.,Yee, Nathan K.,Senanayake, Chris H.
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p. 301 - 307
(2014/05/20)
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- Heterogeneous asymmetric hydrogenation of heteroaromatic methyl ketones catalyzed by cinchona-modified iridium catalysts
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A heterogeneous iridium catalyst was synthesized with silica particles as support for the hydrogenation of heteroaromatic methyl ketones. The catalyst and support were characterized by solid-state NMR, HTEM, SEM, XPS, and BET. A series of heteroaromatic methyl ketones were investigated at room temperature. The catalytic system was effective and more than 99% conversion and up to 83.6% enantioselectivity were obtained in the hydrogenation of heteroaromatic methyl ketones.
- Li, Chun,Zhang, Lin,Zheng, Congye,Zheng, Xueli,Fu, Haiyan,Chen, Hua,Li, Ruixiang
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p. 821 - 824
(2014/06/23)
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- Chiral (η6-p-cymene)ruthenium(II) complexes containing monodentate acylthiourea ligands for efficient asymmetric transfer hydrogenation of ketones
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The new chiral ligands (R)-/(S)-N-((1-phenylethyl)carbamothioyl)benzamide (L1/L2), (R)-/(S)-N-((1-phenylethyl)carbamothioyl)thiophene-2-carboxamide (L3/L4), and (R)-/(S)-N-((1-phenylethyl)carbamothioyl)furan-2-carboxamide (L5/L6) were synthesized, characterized, and used to prepare novel chiral Ru(II) complexes. The chiral Ru(II) complexes 1-6 were obtained from reactions between the chiral ligands L1-L6 and [RuCl2(p-cymene)2] 2. The complexes were characterized by analytical and spectroscopic (NMR, FT-IR, electronic) techniques. The solid-state structures of the ligands L1 and L3 and complexes 1, 4, and 6 were determined by single-crystal X-ray diffraction methods. In all of the complexes, the ligand is bound to the Ru(II) center only via the sulfur donor atom. This monodentate coordination of the acylthiourea ligands was observed for the first time with ruthenium. The Ru(II) complexes 1-6 all act as efficient catalysts for the asymmetric transfer hydrogenation of aromatic ketones in the presence of 2-propanol and KOH to produce chiral alcohols. All of the catalysts showed excellent conversions of up to 99% and enantiomeric excesses of up to 99%.
- Sheeba, Mani Mary,Muthu Tamizh, Manoharan,Farrugia, Louis J.,Endo, Akira,Karvembu, Ramasamy
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p. 540 - 550
(2014/02/14)
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- Second-generation amino acid furanoside based ligands from D-glucose for the asymmetric transfer hydrogenation of ketones
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A novel series of modular amino acid thioamide ligands functionalized with carbohydrates were introduced and employed in the rhodium-catalyzed asymmetric transfer hydrogenation (ATH) of aryl alkyl ketones, including the less-studied heteroaromatic ketones. The ligands are based on amino acid hydroxyamides (pseudodipeptides), which are the most successful ligands previously used in asymmetric hydrogen transfer reactions. High enantioselectivities [up to 99 % enantiomeric excess (ee)] were achieved in the ATH of a wide range of aryl alkyl ketones by using catalysts generated in situ from [RhCl2Cp] 2 (Cp=C5Me5) and thioamide ligands comprising a 3-benzyl glucofuranoside backbone and a bulky isopropyl group in the α-amino acid moiety. Interestingly, both enantiomers of the alcohol products can readily be obtained with high enantioselectivity by simply changing the absolute configuration of the α-amino acid. The good performance can be extended to a very challenging class of industrially interesting heteroaromatic ketones (up to 99 % ee). The next generation: High enantioselectivities are achieved in the asymmetric transfer hydrogenation of a wide range of aryl alkyl ketones by using catalysts generated in situ from [RhCl2Cp]2 (Cp=C5Me5) and thioamide ligands prepared from commercial α-amino acids and D-glucose. The good performance extends to a very challenging class of industrially interesting heteroaromatic ketones. Boc=tert-butoxycarbonyl, Bz=benzoyl. Copyright
- Coll, Mercedes,Pamies, Oscar,Adolfsson, Hans,Dieguez, Montserrat
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p. 3821 - 3828
(2014/01/06)
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- Varying the ratio of formic acid to triethylamine impacts on asymmetric transfer hydrogenation of ketones
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Asymmetric transfer hydrogenation (ATH) is frequently carried out in the azeotropic mixture of formic acid (F) and triethylamine (T), where the F/T molar ratio is 2.5. This study shows that the F/T ratio affects both the reduction rate and enantioselectivity, with the optimum ratio being 0.2 in the ATH of ketones with the Ru-TsDPEN catalyst. Under such conditions, a range of substrates have been reduced, affording high yields and good to excellent enantioselectivities. In comparison with the common azeotropic F-T system, the reduction is faster. This protocol improves both the classic azeotropic and the aqueous-formate system when using water-insoluble ketones.
- Zhou, Xiaowei,Wu, Xiaofeng,Yang, Bolun,Xiao, Jianliang
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experimental part
p. 133 - 140
(2012/05/20)
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- Purification and characterization of an NADH-dependent alcohol dehydrogenase from Candida maris for the synthesis of optically active 1-(pyridyl)ethanol derivatives
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A novel (R)-specific alcohol dehydrogenase (AFPDH) produced by Candida maris IFO10003 was purified to homogeneity by ammonium sulfate fractionation, DEAE-Toyopearl, and Phenyl-Toyopearl, and characterized. The relative molecular mass of the native enzyme was found to be 59,900 by gel filtration, and that of the subunit was estimated to be 28,900 on SDS-polyacrylamide gel electrophoresis. These results suggest that the enzyme is a homodimer. It required NADH as a cofactor and reduced various kinds of carbonyl compounds, including ketones and aldehydes. AFPDH reduced acetylpyridine derivatives, β-keto esters, and some ketone compounds with high enantioselectivity. This is the first report of an NADH-dependent, highly enantioselective (R)-specific alcohol dehydrogenase isolated from a yeast. AFPDH is a very useful enzyme for the preparation of various kinds of chiral alcohols.
- Kawano, Shigeru,Yano, Miho,Hasegawa, Junzo,Yasohara, Yoshihiko
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experimental part
p. 1055 - 1060
(2012/02/03)
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- Highly enantioselective bioreduction of prochiral ketones by stem and germinated plant of Brassica oleracea variety italica
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An eco-friendly and environmentally benign asymmetric reduction of a broad range of prochiral ketones employing Brassica oleracea variety italica (stems and germinated plant) as a novel biocatalyst was developed. It was found that B. oleracea variety italica could be used effectively for enantioselective bioreduction in aqueous medium with moderate to excellent chemical yield and enantiomeric excess (ee). This process is more efficient and generates less waste than conventional chemical reagents or microorganisms. Both R- and S-configurations were obtained by these asymmetric reactions. The best ee were achieved for pyridine derivatives (92-99%). The ee in germinated plant reactions were significantly higher than those of stem reactions. The low cost and the easy availability of these biocatalysts suggest their possible use for large scale preparations of important chiral alcohols.
- Mohammadi, Mehdi,Yousefi, Maryam,Habibi, Zohreh
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experimental part
p. 328 - 336
(2012/03/11)
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- Efficient reduction of ethyl 2-oxo-4-phenylbutyrate at 620 ?l -1 by a bacterial reductase with broad substrate spectrum
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A β-ketoacyl-ACP reductase (FabG) gene from Bacillus sp. ECU0013 was heterologously overexpressed in Escherichia coli and the encoded protein was purified to homogeneity. The recombinant reductase could reduce a broad spectrum of prochiral ketones including aromatic ketones and keto esters and showed the highest activity in the asymmetric reduction of ethyl 2-oxo-4-phenylbutyrate (OPBE). Using E. coli cells coexpressing both FabG and glucose dehydrogenase (GDH) genes, as much as 620 ?L-1 of OPBE was almost stoichiometrically converted to ethyl (S)-2-hydroxy-4-phenylbutyrate [(S)-HPBE] with excellent (>99%) enantiomeric excess. More importantly, the process could be performed smoothly without external addition of an expensive cofactor as usually done and could be scaled up very easily. All these positive features demonstrate the applicability of this reductase for the large-scale production of optically active α-hydroxy acids/esters.
- Ni, Yan,Li, Chun-Xiu,Zhang, Jie,Shen, Nai-Dong,Bornscheuer, Uwe T.,Xu, Jian-He
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supporting information; experimental part
p. 1213 - 1217
(2011/07/09)
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- Copper-dipyridylphosphine-polymethylhydrosiloxane: A practical and effective system for the asymmetric catalytic hydrosilylation of ketones
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In the presence of the inexpensive and non-toxic stoichiometric reductant polymethylhydrosiloxane (PMHS), the chiral copper(II)-dipyridylphosphine catalyst displayed high efficiency in the stereoselective hydrosilylation of a wide scope of aryl alkyl and heteroaromatic ketones under an air atmosphere and mild conditions in good to excellent ees (up to 97%). With certain amounts of sodium tert-butoxide and tert-butyl alcohol as additives, the reaction on a 21-g substrate scale can be conveniently completed within a few hours even at a substrate-to-ligand (S/L) ratio of 50,000. Copyright
- Zhang, Xi-Chang,Wu, Fei-Fei,Li, Shijun,Zhou, Ji-Ning,Wu, Jing,Li, Ning,Fang, Wenjun,Lam, Kim Hung,Chan, Albert S. C.
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supporting information; experimental part
p. 1457 - 1462
(2011/08/03)
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- Asymmetric transfer hydrogenation of prochiral ketones in aqueous media with chiral water-soluble and heterogenized bifunctional catalysts of the RhCp*-type ligand
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Asymmetric transfer hydrogenation (ATH) of prochiral aromatic ketones was carried out with a water-soluble complex of RhIIICp* and mononitrobenzenesulfonamide bidentate ligand (1R,2R)-N-(2-aminocyclohexyl)-4- nitrobenzenesulfonamide 1 derived from chiral cyclohexane-1,2-diamine. Aqueous sodium formate was used as the hydride source. The reaction afforded the chiral alcohols in good enantioselectivities (79-93%) and yields (>99%). The modified monosulfonamide ligand was also covalently immobilized on solid phase such as silica, resin, and mesoporous SBA-15 silica and then explored as a catalyst with RhIIICp* in the ATH of acetophenone. Copyright
- Barron-Jaime, Angelica,Narvaez-Garayzar, Oscar F.,Gonzalez, Jorge,Ibarra-Galvan, Valentin,Aguirre, Gerardo,Parra-Hake, Miguel,Chavez, Daniel,Somanathan, Ratnasamy
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experimental part
p. 178 - 184
(2011/11/06)
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- Chiral pincer ruthenium and osmium complexes for the fast and efficient hydrogen transfer reduction of ketones
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A series of chiral HCNN ligands ((S)-1b-g) (S)-2-(1-aminoethyl)-6-(aryl) pyridine (aryl = 4-MeO-phenyl, 1b; 4-CF3-phenyl, 1c; 3,5-di-Me-phenyl, 1d; 3,5-di-CF3-phenyl, 1e; 1-naphthyl, 1f; 2-naphthyl, 1g) were synthesized starting from commercial 2-acetyl-6- bromopyridine (2), by a chemoenzymatic method involving the dynamic kinetic resolution of the corresponding secondary alcohol (rac-3). The conversion of the resulting (R)-3, obtained in 98% ee, into the homochiral amine ((S)-6), followed by Suzuki coupling with the appropriate arylboronic acids 7b-g, gave access to (S)-1b-g, isolated in 97% ee, with an overall yield up to 50%. The in situ generated pincer complexes [MCl(CNN)(PP)] (M = Ru, Os; PP = Josiphos diphosphine), prepared from [MCl2(PPh3)3], (R,S)-Josiphos diphosphines, and the ligands (S)-1b-g, were found to efficiently catalyze the asymmetric transfer hydrogenation of acetophenone in 2-propanol at 60 °C and in the presence of NaOiPr. On the basis of these data, the 2-naphthyl ruthenium and osmium derivatives [RuCl(CNN)((R,S)-Josiphos*] (8) (HCNN = (S)-1g) and [OsCl(CNN)(PP)] (PP = (R,S)-Josiphos, 9, and (R,S)-Josiphos*, 10) were isolated from [MCl2(PPh 3)3], (R,S)-Josiphos diphosphines, and the ligand (S)-1g. Complexes 8 and 10, displaying the correctly matched chiral PP and CNN - ligands, are highly active and productive catalysts for the transfer hydrogenation of alkyl aryl ketones and methyl pyridyl ketones with TOF = 105-106 h-1, using 0.005 mol % of catalysts and achieving up to 99% ee. The comparison of the catalytic activity of these pincer complexes shows that Ru and Os derivatives display similar rate and enantioselectivity.
- Baratta, Walter,Benedetti, Fabio,Del Zotto, Alessandro,Fanfoni, Lidia,Felluga, Fulvia,Magnolia, Santo,Putignano, Elisabetta,Rigo, Pierluigi
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experimental part
p. 3563 - 3570
(2010/10/03)
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- Iron(ii)-bis(isonitrile) complexes: Novel catalysts in asymmetric transfer hydrogenations of aromatic and heteroaromatic ketones
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Chiral iron(ii)-bis(isonitrile) complexes catalyse the transfer hydrogenation of aromatic ketones with enantioselectivities up to 91% ee, most likely via hydride transfer through imine intermediates, generated by in situ reduction of the isonitrile ligands, whereas iron acts as a Lewis acid to activate the ketone.
- Naik, Anu,Maji, Tapan,Reiser, Oliver
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supporting information; experimental part
p. 4475 - 4477
(2010/11/03)
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- Catalytic asymmetric transfer hydrogenation of ketones using [Ru(p-cymene)Cl2]2 with chiral amino alcohol ligands
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Catalytic asymmetric transfer hydrogenation of aromatic alkyl ketones has been investigated using [Ru(p-cymene)Cl2]2 and new derivatives of β-amino alcohols synthesized from (S)-(-)-lactic acid and mandelic acid as ligands. Chiral secondary alcohols were obtained with good to excellent conversion (60-90%) and moderate to good enantioselectivities (40-86%).
- Deshpande, Sudhindra H.,Kelkar, Ashutosh A.,Gonnade, Rajesh G.,Shingote, Savita K.,Chaudhari, Raghunath V.
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experimental part
p. 231 - 238
(2011/01/12)
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- Novel dimethoxy(aminoalkoxy)borate derived from (S)-diphenylprolinol as highly efficient catalyst for the enantioselective boron-mediated reduction of prochiral ketones
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The novel dimethoxyl(aminoalkoxy)borate 1 was isolated as a white crystalline dimer joined by H-bonding as evidenced by X-ray analysis, and demonstrated to be a highly effective catalyst for the asymmetric reduction of representative prochiral ketones with borane-DMS. Optically pure alcohols were obtained using only 1 mol % of catalyst 1 in up to 99% ee.
- Stepanenko, Viatcheslav,Ortiz-Marciales, Margarita,Barnes, Charles L.,Garcia, Carmelo
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experimental part
p. 995 - 998
(2009/05/31)
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- Application of copper(II)-dipyridylphosphine catalyst in the asymmetric hydrosilylation of simple ketones in air
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Copper (II)-dipyridylphosphine catalyst was used in the asymmetric hydrosilylation of simple ketones under ambient conditions in competitive levels of enantioinduction and activity. The experiment also described the utility of the combination of copper(II) salt/(S)-1/PhSiH3 in the enantioselective hydrosilylation of heteroaromatic ketones and several other ketonic substrates leading to some valuable pharmaceutical and agricultural chemical intermediates. A number of the resulting chiral alcohols represented valuable intermediates for some physiologically active compounds, with remarkable temperature effects on the asymmetric induction were observed in some cases of heteroaromatic ketones. The results show that the present catalyst system features widespread substrate scope, high air stability, fast rate of reaction, good-to-excellent enantioselectivity, and mild conditions thereby affording a practical protocol to a vast selection of optically enriched alcohols.
- Zhang, Xi-Chang,Wu, Yan,Yu, Feng,Wu, Fei-Fei,Wu, Jing,Chan, Albert S. C.
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supporting information; experimental part
p. 5888 - 5891
(2010/03/03)
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- Asymmetric hydrogenation of simple ketones with planar chiral ruthenocenyl phosphinooxazoline ligands
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Ruthenocenyl phosphinooxazoline ligands have been shown to be highly efficient catalysts in the asymmetric hydrogenation. Both simple aromatic and heteroaromatic ketones were examined and excellent conversions and enantioselectivities were achieved.
- Wang, Yanlan,Liu, Delong,Meng, Qinghua,Zhang, Wanbin
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experimental part
p. 2510 - 2512
(2010/03/26)
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- Highly enantioselective carbonyl reduction with borane catalyzed by chiral spiroborate esters derived from chiral beta-aminoalcohols
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Novel spiroborate esters derived from non-recemic 1,2-amino alcohols were examined as chiral catalyst in the borane reduction of acetophenone and other aromatic ketones at room temperature. The optically active alcohols were obtained in excellent chemical yields and up to 99% ee with less than 10% catalyst.
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Page/Page column 6
(2008/12/08)
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- Asymmetric anti-Prelog reduction of ketones catalysed by Paracoccus pantotrophus and Comamonas sp. cells via hydrogen transfer
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A broad range of ketones including methyl-aryl-, methyl-alkyl-, cyclic and sterically hindered ketones were reduced to the corresponding anti-Prelog alcohols with moderate to excellent stereoselectivities by employing lyophilised cells of Paracoccus pantotrophus DSM 11072 and Comamonas sp. DSM 15091 via hydrogen transfer. The reduction equivalents were provided using 2-propanol as a hydride donor. For instance, acetophenone was reduced to the corresponding (R)-enantiomer with >99% ee.
- Lavandera, Ivan,Hoeller, Brigitte,Kern, Alexander,Ellmer, Ursula,Glieder, Anton,de Wildeman, Stefaan,Kroutil, Wolfgang
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p. 1954 - 1958
(2008/12/22)
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- RhIII- and IrIII-catalyzed asymmetric transfer hydrogenation of ketones in water
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Asymmetric transfer hydrogenation (ATH) of ketones by formate in neat water is shown to be viable with Rh-TsDPEN and Ir-TsDPEN catalysts, derived in situ from [Cp*MCl2]2 (M = Rh, Ir) and TsDPEN. A variety of ketones were reduced, including non-functionalized aryl ketones, heteroaryl ketones, ketoesters, and unsaturated ketones. In comparison with IrTsDPEN and the related RuII catalyst, the RhIIIcatalyst is most efficient in water, affording enantioselectivities of up to 99% ee at substrate/catalyst (S/C) ratios of 100-1000 even without working under an inert atmosphere. The aqueous phase reduction is shown to be highly pH-dependent; the optimum pH windows for TOF greater than 50 molmol-1h-1 for Rh- and IrTsDPEN are 5.5-10.0 and 6.5-8.5, respectively. Outside the pH window, the reduction becomes slow or stagnant depending on the pH. However, the enantioselectivities erode only under acidic conditions. At a higher S/C ratio, the aqueous ATH by Rh-TsDPEN is shown to be product- as well as byproduct-inhibited; the product inhibition appears to stem at least partly from the reaction being reversible. The aqueous phase reduction is simple, efficient and environmentally benign, thus presenting a viable alternative for asymmetric reduction.
- Wu, Xiaofeng,Li, Xiaohong,Zanotti-Gerosa, Antonio,Pettman, Allan,Liu, Jianke,Mills, Allan James,Xiao, Jianliang
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scheme or table
p. 2209 - 2222
(2009/04/06)
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- New paracyclophane phosphine for highly enantioselective ruthenium-catalyzed hydrogenation of prochiral ketones
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The synthesis of a new paracyclophane phosphine is described. This ligand was highly efficient in the ruthenium-catalyzed asymmetric hydrogenation of various aromatic and heteroaromatic ketones. Georg Thieme Verlag Stuttgart.
- Cheemala, Murthy N.,Gayral, Maud,Brown, John M.,Rossen, Kai,Knochel, Paul
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p. 3877 - 3885
(2008/09/18)
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- Spiroborate esters in the borane-mediated asymmetric synthesis of pyridyl and related heterocyclic alcohols
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The effectiveness of several spiroborate ester catalysts was investigated in the asymmetric borane reduction of 2-, 3-, and 4-acetylpyridines under different reaction conditions. Highly enantiomerically enriched 1-(2-, 3-, and 4-pyridyl)ethanols and 1-(heterocyclic)ethanols were obtained using 1-10% catalytic loads of the spiroborate 5 derived from diphenylprolinol and ethylene glycol.
- Stepanenko, Viatcheslav,De Jesus, Melvin,Correa, Wildeliz,Guzman, Irisbel,Vazquez, Cindybeth,Ortiz, Lymaris,Ortiz-Marciales, Margarita
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p. 2738 - 2745
(2008/03/27)
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