- Iron(II) Complexes Containing Chiral Unsymmetrical PNP′ Pincer Ligands: Synthesis and Application in Asymmetric Hydrogenations
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Four new chiral PNP′ pincer ligands with a scaffold consisting of a planar chiral ferrocene and a centro chiral aliphatic unit were synthesized and characterized. Treatment of anhydrous FeBr2(THF)2 with 1 equiv of the unsymmetrical chiral PNP′ pincer ligands afforded complexes of the general formula [Fe(PNP′)Br2]. In the solid state these complexes adopt a tetrahedral geometry with the PNP′ ligands coordinated in a ?°2P,N-fashion, as shown by X-ray crystallography. These complexes react with CO in the presence of NaBH4 to yield hydride complexes of the type [Fe(PNP′)(H)(Br)(CO)], which were isolated and tested as catalysts in the asymmetric hydrogenation of ketones. Enantioselectivities of up to 81% ee were obtained.
- Zirakzadeh, Afrooz,Kirchner, Karl,Roller, Alexander,St?ger, Berthold,Widhalm, Michael,Morris, Robert H.
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- Short-Mesochannel SBA-15-Supported Chiral 9-Amino Epicinchonine for Asymmetric Transfer Hydrogenation of Aromatic Ketones
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A short-mesochannel SBA-15 material functionalized with propylthiol groups was prepared by co-condensation and applied to the immobilization of chiral 9-amino epicinchonine. After complexing with [Ir(cod)Cl]2 (cod=1,5-cyclooctadiene), these mesoporous materials were evaluated as catalysts for the asymmetric transfer hydrogenation of aromatic ketones. Higher enantioselectivities and comparable, or even higher, catalytic activities were achieved compared with the free catalyst. Both the short mesochannel and co-condensation approach for short-mesochannel SBA-15 materials functionalized with propylthiol groups, [SSBA-SH(x)] materials were demonstrated to contribute to the excellent catalytic performance. In addition, the catalyst SSBA-AEC(5)/Ir (AEC=9-amino epicinchonine), with low 3-mercaptopropyltrimethoxysilane (MPTMS) content, showed the best catalytic performance; a high enantiomeric excess of 84 % (homogeneous ee=60 %) along with a conversion of 97 % was achieved within 1 h for asymmetric transfer hydrogenation of acetophenone. Moreover, these immobilized catalysts showed high stability during the reaction and could be recovered for reuse.
- Lou, Lan-Lan,Li, Shanshan,Du, Huanling,Zhang, Jiong,Yu, Wenjun,Yu, Kai,Liu, Shuangxi
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- The enantioselective reduction of 2′-fluoroacetophenone utilizing a simplified CBS-reduction procedure
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We have developed a practical, non-enzymatic, catalytic process for the enantioselective reduction of 2′-fluoroacetophenone. A number of catalysts were screened for the oxazaborolidine-type reduction of this ketone to obtain an optimized system. We have s
- Garrett, Christine E,Prasad, Kapa,Repic, Oljan,Blacklock, Thomas J.
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- Novel non-metal catalyst for catalyzing asymmetric hydrogenation of ketone and alpha, beta-unsaturated ketone
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The invention discloses a novel non-metal catalyst for catalyzing asymmetric hydrogenation of ketone and alpha, beta-unsaturated ketone. The preparation method of a chiral alcohol compound shown as formula IV comprises the following step of: reacting a ketone compound shown as formula V with hydrogen under the catalysis of tri(4-hydrotetrafluorophenyl)boron and a chiral oxazoline compound to obtain the chiral alcohol compound shown as the formula IV; the preparation method of a chiral tetralone compound shown as formula VI comprises the following step of: under the catalysis of tri(4-hydrotetrafluorophenyl)boron and a chiral oxazoline compound, reacting an alpha, beta-unsaturated ketone compound shown as formula VII with hydrogen to obtain the chiral tetralone compound shown as the formula VI. The method has the advantages of easy synthesis of raw materials, mild reaction conditions, simple operation, high stereoselectivity and the like, the ee value of the product is up to 92%, and the yield is up to 99%.
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Paragraph 0144-0149
(2021/04/26)
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- Tridentate nitrogen phosphine ligand containing arylamine NH as well as preparation method and application thereof
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The invention discloses a tridentate nitrogen phosphine ligand containing arylamine NH as well as a preparation method and application thereof, and belongs to the technical field of organic synthesis. The tridentate nitrogen phosphine ligand disclosed by the invention is the first case of tridentate nitrogen phosphine ligand containing not only a quinoline amine structure but also chiral ferrocene at present, a noble metal complex of the type of ligand shows good selectivity and extremely high catalytic activity in an asymmetric hydrogenation reaction, meanwhile, a cheap metal complex of the ligand can also show good selectivity and catalytic activity in the asymmetric hydrogenation reaction, and is very easy to modify in the aspects of electronic effect and space structure, so that the ligand has huge potential application value. A catalyst formed by the ligand and a transition metal complex can be used for catalyzing various reactions, can be used for synthesizing various drugs, and has important industrial application value.
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Paragraph 0095-0102; 0105-0109
(2021/06/26)
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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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- Asymmetric Hydrogenation of Ketones and Enones with Chiral Lewis Base Derived Frustrated Lewis Pairs
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The concept of frustrated Lewis pairs (FLPs) has been widely applied in various research areas, and metal-free hydrogenation undoubtedly belongs to the most significant and successful ones. In the past decade, great efforts have been devoted to the synthesis of chiral boron Lewis acids. In a sharp contrast, chiral Lewis base derived FLPs have rarely been disclosed for the asymmetric hydrogenation. In this work, a novel type of chiral FLP was developed by simple combination of chiral oxazoline Lewis bases with achiral boron Lewis acids, thus providing a promising new direction for the development of chiral FLPs in the future. These chiral FLPs proved to be highly effective for the asymmetric hydrogenation of ketones, enones, and chromones, giving the corresponding products in high yields with up to 95 % ee. Mechanistic studies suggest that the hydrogen transfer to simple ketones likely proceeds in a concerted manner.
- Du, Haifeng,Feng, Xiangqing,Gao, Bochao,Meng, Wei
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supporting information
p. 4498 - 4504
(2020/02/05)
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- Control of enantioselectivity in the enzymatic reduction of halogenated acetophenone analogs by substituent positions and sizes
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We utilized acetophenone reductase from Geotrichum candidum NBRC 4597 (GcAPRD), wild type and Trp288Ala mutant, to reduce halogenated acetophenone analogs to their corresponding (S)- and (R)-alcohols beneficial as pharmaceutical intermediates. Reduction by wild type resulted in excellent (S)-enantioselectivity for all of the substrates tested. Meanwhile, reduction by Trp288Ala resulted in high (R)-enantioselectivity for the reduction of 4′ substituted acetophenone and 2′-trifluoromethylacetophenone. In addition to that, we were able to control the enantioselectivity of Trp288Ala by the positions and sizes of the halogen substituents.
- Koesoema, Afifa Ayu,Standley, Daron M.,Ohshima, Shusuke,Tamura, Mayumi,Matsuda, Tomoko
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supporting information
(2020/03/23)
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- Chiral amino-pyridine-phosphine tridentate ligand, manganese complex, and preparation method and application thereof
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The invention discloses a chiral amino-pyridine-phosphine tridentate ligand, a manganese complex, and a preparation method and application thereof. The chiral amino-pyridine-phosphine tridentate ligand is shown as a formula II, and the manganese complex of the chiral amino-pyridine-phosphine tridentate ligand can be used for efficiently catalyzing and hydrogenating ketone compounds to prepare chiral alcohol compounds in a high enantioselectivity mode. The chiral amino-pyridine-phosphine tridentate ligand and the manganese complex are simple in synthesis process, good in stability, high in catalytic activity and mild in reaction conditions.
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Paragraph 0597-0599; 0601
(2020/07/13)
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- Redox-driven deracemization of secondary alcohols by sequential ether/O2-mediated oxidation and Ru-catalyzed asymmetric reduction
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The deracemization of benzylic alcohols has been achieved using a redox-driven one-pot two-step process. The racemic alcohols were oxidized by bis(methoxypropyl) ether and oxygen to give the ketone intermediates, followed by an asymmetric transfer hydrogenation with a chiral ruthenium catalyst. This compatible oxidation/reduction process gave the enantiomerically enriched alcohols with up to 95% ee values.
- Yang, Bing,Cui, Peng,Chen, Yongsheng,Liu, Qixing,Zhou, Haifeng
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supporting information
(2020/10/14)
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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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- 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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- Imine containing C2-Symmetric chiral half sandwich η6-p-cymene-Ru(II)- phosphinite complexes: Investigation of their catalytic activity in the asymmetric transfer hydrogenation of ketones
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New chiral C2-symmetric bis(phosphinite) ligands containing imine group were synthesized from 1-({[(1R,2R)-2-{[(2-hydroxynaphthalen-1-yl)methylidene] amino}cyclohexyl]- imino}methyl)- naphthalen-2-ol and two equivalents of Ph2PCl, (i-Pr)2PCl or (Cy)2PCl, in high yields. Binuclear C2-symmetric half sandwich η6-p-cymene-Ru(II) complexes of the chiral phosphinite ligands were synthesized by treating of [Ru(η6-p-cymene)(μ-Cl)Cl]2 with the phosphinites in 1:1 M ratio in CH2Cl2. Their catalytic activities in asymmetric transfer hydrogenation (ATH) were investigated for the reaction of acetophenone derivatives with isopropyl alcohol. The corresponding optically active secondary alcohols were obtained in excellent levels of conversion (96–99%) and moderate enantioselectivity (up to 60% ee). Among three complexes investigated, complex 4 was the most efficient one.
- Saleh, Najmuldain Abdullah,Pa?a, Salih,Kayan, Cezmi,Meri?, Nermin,Sünkür, Murat,Aral, Tar?k,Aydemir, Murat,Baysal, Ak?n,Durap, Feyyaz
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- Lutidine-Based Chiral Pincer Manganese Catalysts for Enantioselective Hydrogenation of Ketones
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A series of MnI complexes containing lutidine-based chiral pincer ligands with modular and tunable structures has been developed. The complex shows unprecedentedly high activities (up to 9800 TON; TON=turnover number), broad substrate scope (81 examples), good functional-group tolerance, and excellent enantioselectivities (85–98 % ee) in the hydrogenation of various ketones. These aspects are rare in earth-abundant metal catalyzed hydrogenations. The utility of the protocol have been demonstrated in the asymmetric synthesis of a variety of key intermediates for chiral drugs. Preliminary mechanistic investigations indicate that an outer-sphere mode of substrate–catalyst interactions probably dominates the catalysis.
- Zhang, Linli,Tang, Yitian,Han, Zhaobin,Ding, Kuiling
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supporting information
p. 4973 - 4977
(2019/03/17)
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- Method for synthesizing chiral alcohol through deracemization
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The invention relates to a method for synthesizing chiral alcohol (formula I) through deracemization. The preparation method provided by the invention is one-pot asymmetric cascade reaction, and comprises the following steps: 1), with racemic alcohol (formula II) as a raw material and dipropylene glycol dimethyl ether as a solvent, reacting at 120 DEG C for 12 hours, and performing a dehydrogenation reaction to produce intermediate ketone (formula III); and 2), directly adding 2.5mol% of a chiral diamine metal ruthenium complex as a catalyst into a reaction system, with 5 equivalents of sodiumformate as a hydrogen source and a mixed solution of methanol and water as a solvent, reacting at 50 DEG C for 12 hours under the protection of nitrogen, and performing asymmetric transfer hydrogenation to obtain the chiral alcohol (formula I). The method has the advantages of environment-friendly synthesis such as a simple and mild reaction condition, step economy and atomic economy; and in addition, a substrate has a wide application range, the enantioselectivity is high, and the method has a broad application prospect in synthesis of chiral alcohol pharmaceutical intermediates and fine chemical raw materials.
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Paragraph 0044-0046
(2019/07/29)
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- Chiral Frustrated Lewis Pairs Catalyzed Highly Enantioselective Hydrosilylations of Ketones
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A highly enantioselective Piers-type hydrosilylation of simple ketones was successfully realized using a chiral frustrated Lewis pair of tri-tert-butylphosphine and chiral diene-derived borane as catalyst. A wide range of optically active secondary alcohols were furnished in 80%—99% yields with 81%—97% ee's under mild reaction conditions.
- Liu, Xiaoqin,Wang, Qiaotian,Han, Caifang,Feng, Xiangqing,Du, Haifeng
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p. 663 - 666
(2019/05/21)
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- Combined Photoredox/Enzymatic C?H Benzylic Hydroxylations
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Chemical transformations that install heteroatoms into C?H bonds are of significant interest because they streamline the construction of value-added small molecules. Direct C?H oxyfunctionalization, or the one step conversion of a C?H bond to a C?O bond, could be a highly enabling transformation due to the prevalence of the resulting enantioenriched alcohols in pharmaceuticals and natural products,. Here we report a single-flask photoredox/enzymatic process for direct C?H hydroxylation that proceeds with broad reactivity, chemoselectivity and enantioselectivity. This unified strategy advances general photoredox and enzymatic catalysis synergy and enables chemoenzymatic processes for powerful and selective oxidative transformations.
- Betori, Rick C.,May, Catherine M.,Scheidt, Karl A.
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supporting information
p. 16490 - 16494
(2019/11/03)
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- Chiral C2-symmetric η6-p-cymene-Ru(II)-phosphinite complexes: Synthesis and catalytic activity in asymmetric reduction of aromatic, methyl alkyl and alkyl/aryl ketones
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Chiral C2-symmetric bis(phosphinite) ligands and their binuclear ruthenium(II) complexes have been synthesized and used as catalysts in the ruthenium-catalyzed asymmetric transfer hydrogenation of aromatic, methyl alkyl and alkyl/aryl ketones using 2-propanol as both the hydrogen source and solvent in the presence of KOH. Under optimized conditions, all complexes showed high catalytic activity as catalysts in the reduction of various ketones to corresponding chiral secondary alcohols. Products were obtained with high conversions (99%) and moderate to good enantioselectivities (82% ee). Furthermore, C2-symmetric bis(phosphinite) ligands and their binuclear ruthenium(II) complexes were characterized by multinuclear NMR spectroscopy, FT-IR spectroscopy, LC/MS-MS and elemental analysis.
- Karaka?, Duygu Elma,Aydemir, Murat,Durap, Feyyaz,Baysal, Ak?n
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p. 430 - 439
(2017/12/06)
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- Ferrocene based chiral binuclear η6-benzene-Ru(II)-phosphinite complexes: Synthesis, characterization and catalytic activity in asymmetric reduction of ketones
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In the present study, a series of chiral C2-symmetric ferrocenyl based binuclear η6-benzene-Ru(II) complexes bearing diphenylphosphinite and diisopropylphosphinite moieties have been synthesised. The new binuclear η6-benze
- Abdlhmed Al-bayati, Yaser W.,Karaka?, Duygu Elma,Meri?, Nermin,Aydemir, Murat,Durap, Feyyaz,Baysal, Ak?n
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- Proteins as Macromolecular Ligands for Metal-Catalysed Asymmetric Transfer Hydrogenation of Ketones in Aqueous Medium
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Biohybrid catalysts resulting from the dative anchoring of half-sandwich organometallic complexes [M(arene)(H2O)x(Cl)y]n+ (M = RuII, arene = η6-benzene, p-cymene or mesitylene; M = IrIII, RhIII, arene = η5-Cp*; x = 1–3, y = 0–2, n = 0–2) to bovine beta-lactoglobulin (βLG) or hen egg white lysozyme showed unprecedented behaviour. These constructs were shown to catalyse the asymmetric transfer hydrogenation of aryl ketones in water with sodium formate as hydrogen donor at a much faster rate than the complexes alone. Full conversion of the benchmark substrate 2,2,2-trifluoroacetophenone was reached with an ee of 86 % for the most selective biohybrid. Surprisingly, even the crude biohybrid gave a good ee despite the presence of non-protein-bound metal species in the reaction medium. Other aryl ketones were reduced in the same way, and the highest ee was obtained for ortho-substituted acetophenone derivatives. Furthermore, treatment of βLG with dimethyl pyrocarbonate resulted in a noticeable decrease of the activity and selectivity of the biohybrid, indicating that the sole accessible histidine residue (His146) was probably involved in the coordination and activation of Ru(benzene). This work underscores that protein scaffolds are efficient chiral ligands for asymmetric catalysis. The use of sodium formate instead of dihydrogen makes this approach safe, inexpensive and environmentally friendly.
- de Jesús Cázares-Marinero, José,Przybylski, Cédric,Salmain, Michèle
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p. 1383 - 1393
(2018/04/06)
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- Enantioselective Transfer Hydrogenation of Ketones Catalyzed by a Manganese Complex Containing an Unsymmetrical Chiral PNP′ Tridentate Ligand
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Manganese complexes of the types [Mn(PNP′)(Br)(CO)2] and [Mn(PNP′)(H)(CO)2] containing a tridentate ligand with a planar chiral ferrocene and a centro chiral aliphatic unit were synthesized, characterized, and tested in the enantiose
- Zirakzadeh, Afrooz,de Aguiar, Sara R. M. M.,St?ger, Berthold,Widhalm, Michael,Kirchner, Karl
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p. 1744 - 1748
(2017/05/29)
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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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- Iminophenyl Oxazolinylphenylamine for Enantioselective Cobalt-Catalyzed Hydrosilylation of Aryl Ketones
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A new family of chiral iminophenyl oxazolinylphenylamines (IPOPA) was designed and synthesized through three steps from commercially available starting materials. An efficient cobalt-catalyzed asymmetric hydrosilylation of simple ketones with a low catalyst loading of CoCl2 and IPOPA was developed to afford chiral alcohols in good yields with high enantioselectivities.
- Chen, Xu,Lu, Zhan
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supporting information
p. 4658 - 4661
(2016/09/28)
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- PROCESS FOR PRODUCING OPTICALLY ACTIVE SECONDARY ALCOHOL
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[Object] The object of this invention is to provide a method for producing an optically active secondary alcohol at a high optical purity by hydrogenating a substrate carbonyl compound at a high efficiency using as a catalyst a ruthenium complex bearing as a ligand certain optically active diphosphine compound and a readily synthesized amine compound. [Solution] The method of producing an optically active secondary alcohol according to the present invention is characterized in that a substrate carbonyl compound (provided that 3-quinuclidinone, 3-quinuclidinone derivative having a substituent, and a ketone having an aromatic hydrocarbon group and a heterocycle are excluded) is reacted with hydrogen and/or a hydrogen donating compound in the presence of a ruthenium complex selected from the compounds expressed by following general formula (1) RuXYAB (1) [in the general formula (1), X and Y are the same or different from each other and denote a hydrogen atom or an anionic group, A denotes an optically active diphosphine expressed by the general formula (2), B denotes an amine compound expressed by following general formula (3)].
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Page/Page column 0167
(2015/02/19)
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- Asymmetric reduction of ketones catalyzed by α,α-diphenyl-(L)-prolinol modified with imidazolium ionic liquid and BH3·SMe2 as a recoverable catalyst
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The synthesis of α,α-diphenyl-4-trans-hydroxy-(L)-prolinol modified with imidazolium based ionic liquids was carried out with trans-α,α-diphenyl-4-hydroxy-(L)-prolinol, 5-bromovaleric acid or 1,5-dibromopentane and imidazole. α,α-Diphenyl-4-hydroxy-(L)-prolinol modified with imidazolium ionic liquid was treated with BH3·SMe2 which generate 1,3,2-oxazaborolidine, that acts as a catalyst for asymmetric reduction of prochiral ketones. α,α-Diphenyl-4-hydroxy-(L)-prolinol modified with imidazolium ionic liquids (PF6 anion) with BH3?SMe2 found to be an efficient catalyst (10 mol%) for the reduction of the acetophenone, gave 99% yield and 87-84% ee. The catalytic method has wide applicability for a variety of substrates. 1,3,2-oxazaborolidine containing ether linkage ionic liquid was recovered and reused up to 4 cycles with 99-91% yields and 87-81% ee's.
- Chauhan, ManMohan Singh,Singh, Surendra
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p. 184 - 189
(2015/02/19)
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- Ruthenium(II) complexes derived from C2-symmetric ferrocene-based chiral bis(phosphinite) ligands: Synthesis and catalytic activity towards the asymmetric reduction of acetophenones
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Chiral secondary alcohols are very important building blocks and valuable synthetic intermediates both in organic synthesis and in the pharmaceutical industry for producing biologically active complex molecules. A series of new chiral Ru-phosphinite complexes (1, 2, 3, 4, 5, 6, 7, 8) were prepared from chiral C2-symmetric ferrocenyl phosphinites and corresponding chloro complex, [Ru(η6-p-cymene)(μ-Cl)Cl]2. The complexes were characterized using conventional spectroscopic methods. The binuclear complexes were tested as pre-catalysts and were found to be good pre-catalysts for the asymmetric transfer hydrogenation of substituted acetophenones in basic 2-propanol at 82° C, providing the corresponding optically active alcohols with almost quantitative conversion and modest to high enantioselectivities (46-97%). Amongst the all complexes, complex 6 gave the highest ee of 97% in the reduction of 2-methoxyacetophenone to (S)-1-(2-methoxyphenyl)ethanol at 82° C.
- Ak,Durap,Aydemir,Baysal
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p. 764 - 770
(2015/11/09)
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- Facile development of chiral alkenylboranes from chiral diynes for asymmetric hydrogenation of silyl enol ethers
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A facile development of chiral alkenylboranes by the hydroboration of chiral diynes with Piers borane was successfully achieved for the first time. With the combination of the in situ generated chiral alkenylboranes and tri-tert-butylphosphine as frustrated Lewis pair catalysts, the metal-free asymmetric hydrogenation of silyl enol ethers was realized to furnish a wide range of optically active secondary alcohols in high yields and up to 99% ee.
- Ren, Xiaoyu,Li, Gen,Wei, Simin,Du, Haifeng
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p. 990 - 993
(2015/03/18)
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- Cobalt-catalyzed asymmetric hydroboration of aryl ketones with pinacolborane
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The highly enantioselective cobalt-catalyzed hydroboration reaction of aryl ketones with HBpin was developed using iminopyridine oxazoline ligands. Halides, amines, ethers, sulfides, esters and amides are well tolerated under the mild reaction conditions, demonstrating its synthetic advantage. Substituted diaryl ketones could also be hydroborated with high enantioselectivity.
- Guo, Jun,Chen, Jianhui,Lu, Zhan
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supporting information
p. 5725 - 5727
(2015/03/30)
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- RUTHENIUM-DIAMINE COMPLEX AND METHOD FOR PRODUCING OPTICALLY ACTIVE COMPOUND
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Provided is a ruthenium complex that is represented by general formula (1*) and is useful as an asymmetric reduction catalyst. (In the formula, * is an asymmetric carbon atom; R1 is an arenesulfonyl group, and the like; R2 and R3 are a phenyl group, and the like; R10 through R14 are selected from a hydrogen atom, C1-10 alkyl group, and the like, but R10 through R14 are not simultaneously hydrogen atoms; X is a halogen atom and the like; j and k are each either 0 or 1; and j+k is 0 or 2.)
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Paragraph 0129; 0130; 0138; 0139; 0140
(2014/03/24)
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- Facile synthesis of hybrid core-shell nanospheres for the asymmetric transfer hydrogenation of aromatic ketones
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The polymer-inorganic hybrid core-shell nanospheres with N-(para-toluenesulfonyl)-1,2-diphenylethylenediamine in the core and the poly(methyl acrylate) (PMA) polymer in the shell were prepared by using a sol-gel process. The surface properties of solid catalysts were modified by controlling PMA and the cetyltrimethylammonium bromide surfactant in the shell. The water contact angle results suggest that the presence of PMA and cetyltrimethylammonium bromide in the shell increases the surface hydrophobicity. In the Rh-catalyzed transfer hydrogenation of aromatic ketones in aqueous HCOONa, the solid catalyst with higher surface hydrophobicity demonstrates higher activity, which suggests that suitable surface properties increase the reaction rate by increasing the diffusion rates of hydrophobic substrates. Furthermore, this heterogeneous catalyst can be reused conveniently without loss of ee values. Clever condensation: A sol-gel process is used for the synthesis of polymer-inorganic hybrid core-shell composites with a mixture of poly(methyl acrylate)-organosilane (PMA SiO2) and tetraethoxysilane as a co-condensed silane source and the polystyrene-supported N-(para-toluenesulfonyl)-1,2-diphenylethylenediamine-type ligand as a polymer core. These core-shell materials demonstrate high reactivity and excellent ee values for the asymmetric transfer hydrogenation of aromatic ketones in aqueous HCOONa.
- Wei, Juan,Zhang, Xiaomin,Zhang, Xiaoming,Zhao, Yaopeng,Li, Ruixiang,Yang, Qihua
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p. 1368 - 1374
(2014/05/20)
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- Hydrogen: A good partner for rhodium-catalyzed hydrosilylation
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The influence of hydrogen pressure on the hydrosilylation of ketones catalyzed by [((S)-SYNPHOS)Rh(nbd)]OTf has been studied. We have notably demonstrated that hydrogen significantly affected the outcome of the reaction while not being consumed as stoichiometric reducing agent. In THF, diethyl ether or toluene, the hydrogen pressure exceedingly accelerated the hydrosilylation reaction and preserved or even improved the enantioselectivity of the process. In CH2Cl2, the rhodium catalyst also showed generally higher catalytic activity under hydrogen pressure. Most serendipitously, several ketones were found to give products of absolute opposite configuration upon performing the hydrosilylation under argon atmosphere or under hydrogen pressure. Copyright 2014 John Wiley & Sons, Ltd. We have shown that the performances of a rhodium complex associated with the atropisomeric diphosphine SYNPHOS as chiral ligand can be considerably upgraded under hydrogen pressure. Most serendipitously, several ketones were found to give the products of absolute opposite configuration upon performing the hydrosilylation under argon atmosphere or under H2 pressure. Copyright
- Balan, Cedric,Pop, Roxana,Comte, Virginie,Poinsot, Didier,Ratovelomanana-Vidal, Virginie,Gendre, Pierre Le
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p. 517 - 522
(2014/07/07)
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- Imidazolium ion tethered TsDPENs as efficient water-soluble ligands for rhodium catalyzed asymmetric transfer hydrogenation of aromatic ketones
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An imidazolium ion tethered TsDPEN has been synthesized readily and used as a water-soluble ligand for [Cp*RhCl2]2 catalyzed asymmetric transfer hydrogenation (ATH) of aromatic ketones in water. This process provided the secondary alcohols in moderate to excellent conversions (up to 100%) with high enantioselectivities (up to 98% ee) under mild reaction conditions without adding any surfactants. The catalytic system is highly effective with the substrate to catalyst (S/C) ratio of 500 and low hydride donor loading of 1.5 equiv. of HCO2Na. The procedure presented is simple and makes this method suitable for practical use.
- Kang, Guowei,Lin, Silong,Shiwakoti, Atul,Ni, Bukuo
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p. 111 - 114
(2014/11/08)
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- Imidazolium ion tethered TsDPENs as efficient water-soluble ligands for rhodium catalyzed asymmetric transfer hydrogenation of aromatic ketones
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An imidazolium ion tethered TsDPEN has been synthesized readily and used as a water-soluble ligand for [Cp?RhCl2]2catalyzed asymmetric transfer hydrogenation (ATH) of aromatic ketones in water. This process provided the secondary alcohols in moderate to excellent conversions (up to 100%) with high enantioselectivities (up to 98% ee) under mild reaction conditions without adding any surfactants. The catalytic system is highly effective with the substrate to catalyst (S/C) ratio of 500 and low hydride donor loading of 1.5 equiv. of HCO2Na. The procedure presented is simple and makes this method suitable for practical use.
- Kang, Guowei,Lin, Silong,Shiwakoti, Atul,Ni, Bukuo
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p. 111 - 114
(2014/12/11)
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- A highly enantioselective hydrogenation of silyl enol ethers catalyzed by chiral frustrated lewis pairs
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Using a simple combination of tri-tert-butylphosphine and chiral borane generated in situ by the hydroboration of chiral diene with HB(C 6F5)2 as a frustrated Lewis pair catalyst, a highly enantioselective metal-free hydrogenation of silyl enol ethers was successfully realized to furnish a variety of optically active secondary alcohols in 93-99% yields with 88->99% ees.
- Wei, Simin,Du, Haifeng
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p. 12261 - 12264
(2014/10/16)
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- Use of tridentate TsDPEN/pyridine ligands in ruthenium-catalysed asymmetric reduction of ketones
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A series of enantiomerically pure tridentate ligands based on the 1,2-diphenylethane-1,2-diamine structure, containing additional pyridine groups, was prepared and tested in asymmetric transfer hydrogenation of ketones using Ru3(CO)12 as a metal source. Alcohols were formed in up to 93% ee in the best cases, and good results were obtained with ortho-haloarylketones.
- Darwish, Moftah O.,Wallace, Alistair,Clarkson, Guy J.,Wills, Martin
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supporting information
p. 4250 - 4253
(2013/07/26)
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- Metal-conjugated affinity labels: A new concept to create enantioselective artificial metalloenzymes
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How to train a protein: Metal-conjugated affinity labels were used to selectively position catalytically active metal centers in the binding pocket of proteases. The resulting artificial metalloenzymes achieve up to 82% e.r. in the hydrogenation of ketone
- Reiner, Thomas,Jantke, Dominik,Marziale, Alexander N.,Raba, Andreas,Eppinger, Jcrg
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- Separation of enantiopure m-substituted 1-phenylethanols in high space-time yield using Bacillus subtilis esterase
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A recombinant Bacillus subtilis esterase (BsE) expressed in E. coli was found to exhibit excellent enantioselectivity (E was always greater than 100) towards m-substituted 1-phenylethanol acetates in the enantioselective hydrolysis reaction. An explanation for the high enantioselectivity observed towards these substrates was provided by molecular modeling. Moreover, the BsE also showed strong tolerance towards a high concentration of m-substituted 1-phenylethanol acetates (up to 1 M). Based on these excellent catalytic properties of BsE, a kind of m-substituted 1-phenylethanols, (R)-1-(3-chlorophenyl)ethanol, was efficiently synthesized in space-time yield of 920 g per L per day and 97% ee, indicating that the BsE was considered as a potentially ideal and promising biocatalyst for large-scale production of optically active m-substituted 1-phenylethanols. The Royal Society of Chemistry 2013.
- Zheng, Gao-Wei,Liu, Xu-Yun,Zhang, Zhi-Jun,Tian, Ping,Lin, Guo-Qiang,Xu, Jian-He
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p. 20446 - 20449
(2013/11/06)
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- Catalyst development for organocatalytic hydrosilylation of aromatic ketones and ketimines
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A new family of Lewis basic 2-pyridyl oxazolines have been developed, which can act as efficient organocatalysts for the enantioselective reduction of prochiral aromatic ketones and ketimines with trichlorosilane, a readily available and inexpensive reagent. 1-Isoquinolyl oxazoline, derived from mandelic acid, was identified as the most efficient catalyst of the series, capable of delivering high enantioselectivities in the reduction of both ketones (up to 94% ee) and ketimines (up to 89% ee).
- Malkov, Andrei V.,Stewart-Liddon, Angus J. P.,McGeoch, Grant D.,Ramirez-Lopez, Pedro,Kocovsky, Pavel
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experimental part
p. 4864 - 4877
(2012/07/28)
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- A new chiral sulfinyl-NH-pyridine ligand for Ir-catalyzed asymmetric transfer hydrogenation reaction
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A new flexible C1-symmetric tridentate ligand (S)-N-(2-(tert-butylsulfinyl)benzyl)-1-(pyridin-2-yl)methanamine sulfoxide (L1) was successfully prepared and utilized as a chiral ligand for Ir(I)-catalyzed ATH (asymmetric transfer hydrogenation) reactions. Without any cooperation of other chiral center, encouraging ee and conversion values have been achieved, which provide us a better understanding on these types of ligands and a new strategy to develop new high-efficiency chiral catalysts for asymmetric reaction.
- Tang, Lei,Wang, Qiwei,Wang, Juanjuan,Lin, Zechao,Wang, Xiaobei,Cun, Linfeng,Yuan, Weicheng,Zhu, Jin,Liao, Jian,Deng, Jingen
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scheme or table
p. 3839 - 3842
(2012/08/14)
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- Ruthenium complexes of phosphino-substituted ferrocenyloxazolines in the asymmetric hydrogenation and transfer hydrogenation of ketones: A comparison
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Three novel routes have been developed for the synthesis of ferrocenyl-based phosphino-oxazolines in which the phosphino unit is attached to a ferrocenylmethyl or a ferrocenylethyl side chain. In two of the routes the phosphino-substituted ethyl side chain was built up diastereoselectively. Ruthenium complexes of the type [RuCl2PPh3(L)] of 12 bidentate phosphine-oxazoline ligands were synthesized, characterized, and tested in the transfer hydrogenation of acetophenone. For the best performing complexes a total of 12 additional ketones were screened in transfer hydrogenations and hydrogenations under transfer hydrogenation conditions. Two catalyst precursors in particular delivered products with an enantiomeric excess of up to 98% in transfer hydrogenations and 99% ee in hydrogenations. The transfer hydrogenation results obtained with all novel ligands were compared to those of two well-established FOXAP ligands. Furthermore, a qualitative comparison with the hydrogenation data was carried out. In both cases surprising similarities in product enantiomeric excess and product absolute configuration were found. Attempts were made to rationalize some of the observed features by considering a transition-state model. The molecular structures of one synthesis intermediate, two catalyst precursors, and two corresponding acetonitrile complexes were studied by X-ray diffraction.
- Zirakzadeh, Afrooz,Schuecker, Raffael,Gorgas, Nikolaus,Mereiter, Kurt,Spindler, Felix,Weissensteiner, Walter
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experimental part
p. 4241 - 4250
(2012/08/08)
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- PEG-400-H2O as a green and recyclable medium for asymmetric hydrogenations of aromatic ketones catalyzed by RuCl2(TPPTS) 2-(S,S)-DPENDS
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PEG-400-H2O was found to be a green and recyclable reaction medium for asymmetric hydrogenations of aromatic ketones catalyzed by a ruthenium achiral monophosphine complex RuCl2(TPPTS)2 [TPPTS: P(m-C6H4SO3Na)3] modified by (S,S)-DPENDS [disodium salt of sulfonated (S,S)-1,2-diphenyl-1,2-ethylene- diamine]. The acetophenone product was obtained with 86.3% ee under the optimized conditions. The resulting products can be easily separated from the catalyst by extraction with n-hexane. The catalyst immobilized in PEG-400-H 2O not only exhibits excellent activity and enantioselectivity, but also can be recycled and reused several times without a loss of activity or enantioselectivity.
- Qin, Ruixiang,Wang, Jinbo,Xiong, Wei,Chen, Hua,Feng, Jian,Liu, Derong
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experimental part
p. 834 - 837
(2012/10/07)
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- Application of ruthenium complexes of triazole-containing tridentate ligands to asymmetric transfer hydrogenation of ketones
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The synthesis of a series of tridentate ligands based on a homochiral 1,2-diamine structure attached to a triazole group and their subsequent applications to the asymmetric transfer hydrogenation of ketones are described. In the best cases, alcohols of up to 93% ee were obtained. Although base is not required, the use of Ru3(CO)12 as metal source is essential, indicating a unique mechanism for the formation of the active catalyst.
- Johnson, Tarn C.,Totty, William G.,Wills, Martin
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supporting information
p. 5230 - 5233,4
(2012/12/12)
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- Application of ruthenium complexes of triazole-containing tridentate ligands to asymmetric transfer hydrogenation of ketones
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The synthesis of a series of tridentate ligands based on a homochiral 1,2-diamine structure attached to a triazole group and their subsequent applications to the asymmetric transfer hydrogenation of ketones are described. In the best cases, alcohols of up to 93% ee were obtained. Although base is not required, the use of Ru3(CO)12 as metal source is essential, indicating a unique mechanism for the formation of the active catalyst.
- Johnson, Tarn C.,Totty, William G.,Wills, Martin
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supporting information
p. 5230 - 5233
(2013/01/15)
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- High activity iridium catalyst for the asymmetric hydrogenation of aromatic ketones
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The asymmetric hydrogenation of aromatic ketones catalyzed by iridium complexes was investigated in the presence of chiral damines and achiral phosphines. The catalytic system with triphenylphosphine and 9-amino(9-deoxy)epicinchonine exhibited high activity and enantioselectivity in the asymmetric hydrogenation of simple aromatic ketones. A series of simple aromatic ketones were hydrogenated completely in just 2 h at room temperature with good ee value (up to 87%).
- Li, Chun,Zhang, Lin,Du, You,Zheng, Xue-Li,Fu, Hai-Yan,Chen, Hua,Li, Rui-Xiang
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- Enantioselective oxidation of racemic secondary alcohols catalyzed by chiral Mn(iii)-salen complexes with N-bromosuccinimide as a powerful oxidant
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We demonstrate an efficient enantioselective oxidation of secondary alcohols catalyzed by Mn(iii)-salen complex using N-bromosuccinimide (NBS) as the oxidant. The new protocol is very efficient for the oxidative kinetic resolution of a variety of secondary alcohols, including ortho-substituted benzylic alcohols. The Royal Society of Chemistry 2012.
- Xu, Daqian,Wang, Shoufeng,Shen, Zhiqiang,Xia, Chungu,Sun, Wei
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supporting information
p. 2730 - 2732
(2012/11/07)
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- Exploiting the enzymatic machinery of Arthrobacter atrocyaneus for oxidative kinetic resolution of secondary alcohols
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We evaluated Arthrobacter atrocyaneus (R1AF57) as producer of oxidoreductases for oxidative kinetic resolution of racemic secondary alcohols via oxidation reaction. This bacterium was isolated from Amazon soil samples using medium enriched with (RS)-1-(4-methylphenyl)ethanol as a carbon source. The kinetic resolution of several secondary alcohols through enantioselective oxidation mediated by resting cells and growing cells of A. atrocyaneus was efficiently achieved for the most alcohols. In general, it was possible to obtain only the (S)-enantiomer from (RS)-1-arylethanols.
- Silva, Camila R.,Souza, Juliana C.,Araujo, Lidiane S.,Kagohara, Edna,Garcia, Thais P.,Pelizzari, Vivian H.,Andrade, Leandro H.
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- BIARYL DIPHOSPHINE LIGANDS, INTERMEDIATES OF THE SAME AND THEIR USE IN ASYMMETRIC CATALYSIS
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The present disclosure relates to biaryl diphosphine ligands of the formula (B), processes for the production of the ligands and the use of the ligands in metal catalysts for asymmetric synthesis. The disclosure also relates to intermediates used for the production of the biaryl diphosphine ligand. (Formula (B))
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Page/Page column 56; 69
(2012/03/27)
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- Ruthenium(II) pyrazolyl-pyridyl-oxazolinyl complex catalysts for the asymmetric transfer hydrogenation of ketones
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Lowering the ketone: RuII complexes containing a chiral pyridyl-based 1H-pyrazolyl-oxazolinyl NNN ligand were synthesized and structurally characterized by X-ray crystallographic studies. These complex catalysts efficiently catalyzed the asymmetric transfer hydrogenation of ketones, reaching up to 99a % ee for the desired products (see scheme). Copyright
- Ye, Wenjing,Zhao, Miao,Yu, Zhengkun
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supporting information; experimental part
p. 10843 - 10846
(2012/09/10)
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- Preparation of surface molecularly imprinted Ru-complex catalysts for asymmetric transfer hydrogenation in water media
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Molecularly imprinted Ru-complex catalysts acting in water were prepared on a SiO2 surface by molecular imprinting of a SiO2- supported Ru-complex using organic polymers as surface matrix overlayers. (R)-1-(o-fluorophenyl)ethanol, which is one of the hydrogenated products of o-fluoroacetophenone, was imprinted on the supported Ru-complex as a template, and an active Ru-complex with a shape-selective reaction space (molecularly imprinted cavity) was prepared inside the wall of the hydrophobic organic polymer matrix overlayers. Structures of the SiO2-supported and molecularly imprinted Ru catalysts were characterized by means of solid-state NMR, XPS, XRF, ICP, UV/vis, XAFS, TGA, and SEM. The molecularly imprinted Ru catalysts exhibited fine shape selectivity and enantioselectivity for the asymmetric transfer hydrogenation of o-fluoroacetophenone and its derivatives.
- Weng, Zhihuan,Muratsugu, Satoshi,Ishiguro, Nozomu,Ohkoshi, Shin-Ichi,Tada, Mizuki
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experimental part
p. 2338 - 2347
(2011/05/04)
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- COMPOUNDS AS LYSOPHOSPHATIDIC ACID RECEPTOR ANTAGONISTS
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Described herein are compounds that are antagonists of lysophosphatidic receptor(s). Also described are pharmaceutical compositions and medicaments that include the compounds described herein, as well as methods of using such antagonists, alone and in combination with other compounds, for treating LPA-dependent or LPA-mediated conditions or diseases.
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Page/Page column 110
(2011/02/24)
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- Ruthenium(II)-catalyzed asymmetric transfer hydrogenation using unsymmetrical vicinal diamine-based ligands: Dramatic substituent effect on catalyst efficiency
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The use of unsymmetrical vicinal diamines as ligands for Ru-catalyzed asymmetric transfer hydrogenation is described. With a SmI2-mediated cross-coupling protocol, a series of enantiomerically pure unsymmetrical vicinal diamines were readily prepared and examined in the asymmetric transfer hydrogenation. It was found that an aromatic substituent on the carbon bearing the-NHTs group and a bulky alkyl substituent on the other side, are both very important for the effectiveness of the ligand, suggesting that the substituent has a dramatic effect on the catalyst efficiency. With ligand 8, excellent enantioselectivities that are comparable to N-tosyl-1,2-diphenylethane-1,2- diamine (TsDPEN) were achieved. The results provide some helpful information on the mechanism of Ru-catalyzed asymmetric transfer hydrogenation. A series of unsymmetrical vicinal diamines were prepared and examined as chiral ligands for Ru-catalyzed asymmetric transfer hydrogenation.
- Zhang, Bo,Wang, Hui,Lin, Guo-Qiang,Xu, Ming-Hua
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scheme or table
p. 4205 - 4211
(2011/09/14)
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