- Enantioselective hydrogenation of β-aryl-β-ketoester over α-hydroxy acid-modified Raney nickel catalysts: competitive hydrogenation with methyl acetoacetate
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The enantioselective hydrogenation of the aromatic β-ketoesters, methyl 3-phenyl-3-oxypropanoate (1) and its p-methoxy-analogue (2), was studied over tartaric acid-modified Raney nickel catalysts. A competitive hydrogenation approach was used to clarify the catalytic behaviors of the enantio-differentiating hydrogenation of aromatic β-ketoesters over tartaric acid-modified Raney nickel, malic acid-modified Raney nickel, and unmodified Raney nickel in comparison with aliphatic one, represented by methyl acetoacetate. We found that the enantioselectivity could be elucidated by the interaction modes between the surface modifier, Ni metal surface, and the substrate as well as the keto/enol ratio of the substrate. We suggest that the moderate enantioselectivity of 1 over tartaric acid-modified Raney nickel is the result of distorted, weak two-point hydrogen bond interactions with surface tartrate due to unfavorable phenyl–Ni metal surface interactions. The p-methoxy group of 2 suppresses the phenyl–Ni metal surface interactions, resulting in an increase in the enantioselectivity of 2 over tartaric acid-modified Raney nickel. Ligand acceleration effects were observed with methyl acetoacetate and 2 but not with 1.
- Choliq, Azka Azkiya,Watanabe, Junya,Misaki, Tomonori,Okamoto, Yasuaki,Sugimura, Takashi
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- Iridium-catalyzed asymmetric hydrogenation of β-keto esters with new phenethylamine-derived tridentate P,N,N-ligands
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A new class of phenethylamine-derived tridentate P,N,N-ligands has been successfully developed. These ligands exhibited good performance in the Ir-catalyzed asymmetric hydrogenation of β-keto esters, affording the corresponding β-hydroxy esters in moderat
- Wei, De-Quan,Chen, Xiu-Shuai,Hou, Chuan-Jin,Hu, Xiang-Ping
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- Chiral Nitroarenes as Enantioselective Single-Electron-Transfer Oxidants for Carbene-Catalyzed Radical Reactions
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A new class of chiral oxidants is developed. These readily accessible oxidants contain a nitro group for oxidation and a chiral sulfonamide moiety for stereoselectivity control. The chiral information from the oxidants can effectively transfer to the substrates in carbene-catalyzed β-hydroxylation of enals via single-electron-transfer radical processes. We expect these oxidants to find unique applications in other asymmetric oxidations and oxygen-atom-transferring reactions.
- Wang, Hongling,Wang, Yuhuang,Chen, Xingkuan,Mou, Chengli,Yu, Shuyan,Chai, Huifang,Jin, Zhichao,Chi, Yonggui Robin
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supporting information
p. 7440 - 7444
(2019/10/02)
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- On the basis of the phenethylamine skeleton chiral P, N, N ligand compound and its manufacturing method and application (by machine translation)
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The present invention provides a chiral P based on the skeleton of the phenethylamine, N, N ligand compound and its manufacturing method and application, surfactant-ethylamine skeleton chiral P, N, N ligand compound of preparation method is as follows: under the protection of nitrogen, the chiral phenylethylamine - [...] compound with 2 - chloromethyl oxazole oxazoline compounds soluble in the reaction solvent, adding alkali, reflux reaction, filtering, desolvation, column chromatography to obtain the required chiral P, N, N ligand compound. In particular to the β - ketoacid ester compound in asymmetric catalytic hydrogenation reaction. The invention of the phenethylamine skeleton chiral P, N, β - keto ester N ligand can be applied to the asymmetric catalytic hydrogenation reaction, can be high yield and high enantio-selectively for the preparation of chiral β - hydroxy ester. (by machine translation)
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Paragraph 0105; 0115; 0116; 0153-0158; 0160
(2019/06/13)
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- Method for preparing chiral beta-hydroxy ester by Ir-catalyzed asymmetric hydrogenation
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The invention provides a method for preparing a chiral beta-hydroxy ester compound by Ir-catalyzed asymmetric hydrogenation. The method for preparing the chiral beta-hydroxy ester compound comprises the steps as follows: in a glove box filled with nitrogen, [Ir(COD)Cl]2 and a chiral P, N, N ligand are dissolved in anhydrous methanol, stirring is performed at room temperature for 1 hour, and a Ir catalyst is generated; substrate beta-ketoester and a base additive are added, the mixture is placed in an autoclave and hydrogenated under certain reaction pressure; hydrogen gas is slowly released, separation with a silica gel column is performed after a solvent is removed, and product beta-hydroxy ester is obtained. The reaction for preparing chiral beta-hydroxy ester by Ir-catalyzed asymmetrichydrogenation of beta-ketoester has the advantages that conditions are mild, operation is easy, enantioselectivity of the product is high and the like.
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Paragraph 0091; 0093; 0094
(2018/06/26)
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- Ir-catalyzed asymmetric hydrogenation of β-keto esters with chiral ferrocenyl P,N,N-ligands
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The Ir-catalyzed asymmetric hydrogenation of β-keto esters with chiral ferrocenyl P,N,N-ligands has been developed. Under the optimized conditions, a wide range of β-keto esters were hydrogenated to afford the corresponding β-hydroxy esters in good to excellent enantioselectivities (up to 95% ee).
- Chen, Xiu-Shuai,Hou, Chuan-Jin,Qin, Chao,Liu, Hongzhu,Liu, Yan-Jun,Huang, De-Zhi,Hu, Xiang-Ping
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p. 12871 - 12875
(2017/03/11)
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- BUTENOLIDES, PROCESS FOR PREPARING THE SAME AND PHARMACEUTICAL COMPOSITION CONTAINING THE SAME
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The present invention relates to: a butenolide-based compound; a stereoisomer thereof; an enantiomer thereof; an in vivo hydrolyzable precursor thereof or a pharmaceutically acceptable salt thereof; and the antibacterial activity, immune disease treatment; and prevention efficacy, the cancer prevention or treatment efficacy, and the preventive activity with respect to the fouling of a medical insertion instrument thereof.
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Paragraph 0345-0348
(2021/06/01)
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- Studies on the chemoenzymatic synthesis of (R)- and (S)-methyl 3-aryl-3-hydroxypropionates: The influence of toluene-pretreatment of lipase preparations on enantioselective transesterifications
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Two series (para- and meta-substituted) of racemic methyl esters of 3-aryl-3-hydroxypropionic acid were prepared after which the enantiomers were separated by an enzyme-catalyzed transesterification. Several lipases were investigated as the catalyst. The influence of the enzyme pretreatment, as well as substrate concentration, reaction temperature, stirring manner, and substrate conversion on the stereochemical outcome of the biotransformation process were investigated in detail. The best results were achieved by using solvent-pretreated lipase from Pseudomonas fluorescens or Burkholderia cepacia suspended in toluene, and vinyl acetate as the acetyl group donor.
- Borowiecki, Pawel,Bretner, Maria
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p. 925 - 936
(2013/09/23)
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- Enantioselective catalysis with a chiral, phosphane-containing PMO material
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A novel bistriethoxysilyl-BINAP monomer was prepared and co-condensed with a biphenylene-bridged siloxane precursor in the presence of surfactant templates to give periodic mesoporous organosilicas (PMOs) functionalized with BINAP. Complexation of ruthenium followed by asymmetric catalytic hydrogenation and asymmetric transfer hydrogenation were carried out, and demonstrated that high levels of activity and selectivity are achievable with the chiral material.
- Seki, Tomohiro,McEleney, Kevin,Crudden, Cathleen M.
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scheme or table
p. 6369 - 6371
(2012/08/14)
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- A one-pot silyl-Reformatsky olefination
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A novel one-pot olefination reaction has been developed, involving the stereoselective formation of (E)-α,β-unsaturated esters/ketones from the reaction of α-bromocarbonyl compounds with aromatic aldehydes. The reactions use a reagent combination of trichlorosilane, and triethylamine and may proceed via the in situ formation of a trichlorosilyl ketene acetal. The general procedure offers key advantages (high conversions, low quantities of organic soluble by-products) over the conventional Wittig reaction.
- Smith, James M.,Greaney, Michael F.
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p. 8687 - 8690
(2008/03/14)
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- Enantioselective hydrogenation of β-ketoesters using a MeO-PEG-supported Biphep ligand under atmospheric pressure: A practical synthesis of (S)-fluoxetine
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The preparation of a novel chiral 2,2′-bis(MeO-PEG-supported)-6, 6′-bis(diphenylphosphanyl)biphenyl (MeO-PEG-Biphep) ligand is described. The derived ruthenium complex catalyzes the hydrogenation of β-ketoesters in up to 99% yield and 99% ee under atmospheric pressure. The accelerating effects exerted by the PEG linkage are dramatic when compared to the unsupported analogue, MeO-Biphep-RuBr2. Furthermore, the catalyst can be recovered easily and the recycled catalysts were shown to maintain their efficiency in two consecutive runs, albeit with declining activity. One of the products, (S)-ethyl-3-hydroxy-3-phenylpropanoate, is useful in the preparation of (S)-fluoxetine. Georg Thieme Verlag Stuttgart.
- Chai, Liting,Chen, Huansheng,Li, Zhiming,Wang, Quanrui,Tao, Fenggang
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p. 2395 - 2398
(2008/02/09)
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- Candida Rugosa lipase-catalyzed kinetic resolution of β-hydroxy- β-arylpropionates and δ-hydroxy-δ-aryl-β-oxo-pentanoates
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A simple and convenient method was reported for the preparation of optically active β-hydroxy-β-arylpropionates, δ-hydroxy-δ- aryl-β-oxo-pentanoates and their butyryl derivatives via CRL-catalyzed hydrolysis. The optically active products are potential precursors of some chiral pharmaceuticals and natural products.
- Xu, Chengfu,Yuan, Chengye
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p. 2169 - 2186
(2007/10/03)
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- Enantioselective Hydrogenation of β-Keto Esters using Chiral Diphosphine-Ruthenium Complexes: Optimization for Academic and Industrial Purposes and Synthetic Applications
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Enantioselective hydrogenation using chiral complexes between atropisomeric diphosphines and ruthenium is a powerful tool for producing chiral compounds. Using a simple and straightforward in situ catalyst preparation, the conditions were optimized using molecular hydrogen for both academic and industrial purposes. This led to the best conditions and the lowest catalytic ratio required for the pressure used. Hydrogenation of various β-keto esters was efficiently performed at atmospheric and higher pressures, leading to the use of very low catalyst-substrate ratios up to 1/20,000. Asymmetric hydrogenations were used in key-steps towards the total synthesis of corynomycolic acid, Duloxetine and Fluoxetine.
- Ratovelomanana-Vidal,Girard,Touati,Tranchier,Ben Hassine,Genet
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p. 261 - 274
(2007/10/03)
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- Indium mediated reactions in water: Synthesis of β-hydroxyl esters
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A variety of β-hydroxyl esters were synthesized efficiently through indium mediated carbon-carbon bond formation in water followed by ozonolysis.
- Yi, Xiang-Hui,Meng, Yue,Li, Chao-Jun
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p. 4731 - 4734
(2007/10/03)
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- Asymmetric reduction of aromatic ketones. II. An enantioselective synthesis of methyl (2R,3S)-3-(4-methoxyphenyl)glycidate
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Asymmetric reduction of some 3-keto esters (6, 8, and 11) to 3-hydroxy esters (7, 9, and 12) with various chiral reducing agents was investigated. The products (9 and 12) were converted to methyl (2R,3S)-3-(4-methoxyphenyl)glycidate (2R,3S-3), a key intermediate in the practical enantioselective synthesis of diltiazem (1).
- Matsuki,Sobukawa,Kawai,Inoue,Takeda
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p. 643 - 648
(2007/10/02)
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- Synthesis of Shikonin and Alkannin
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The enantiomeric naturally occurring naphthoquinones shikonin and alkannin have been synthesized in a thirteen-step procedure in 44 to 65percent e.e.The stereogenic centers of (R)-1 and (S)-1 are created by the reaction of naphthaldehyde 3 with (R)- and (S)-2-hydroxy-1,2,2-triphenylethyl acetate (2), respectively.In order to find out a rationalization for the unexpectedly low diastereoselectivity in this aldol addition, a series of substituted aromatic aldehydes 12a-h has been treated with (R)-2. Key words: Naphthoquinone / Aldol addition / (R)-Shikonin / (S)-Alkannin
- Braun, Manfred,Bauer, Claus
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p. 1157 - 1164
(2007/10/02)
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