- Sinapyl alcohol derivatives from the lipo-soluble part of Dichrocephala benthamii C. B. Clarke
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Four new sinapyl alcohol derivatives dichrocephols A-D (compounds 1-4) were isolated from the lipo-soluble part of the whole herb of Dichrocephala benthamii C. B. Clarke, together with the known compound syringenin isovalerate (5). Their structures were elucidated on the basis of spectroscopic analysis. Their absolute configurations were established by the method of alkaline hydrohysis. Compounds 1-3 showed moderate cytotoxity against HeLa cells, with IC50 values of 14.8 μM, 51.6 μM and 81.6 μM, respectively. This is the first time that sinapyl alcohol derivatives were isolated from the genus Dichrocephala.
- Tian, Xinhui,Ding, Gang,Peng, Chaozhong,Hu, Yanbao,Li, Li,Chen, Hong,Zou, Zhongmei
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Read Online
- Asymmetric hydrogenation of an α-unsaturated carboxylic acid catalyzed by intact chiral transition metal carbonyl clusters-diastereomeric control of enantioselectivity
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Twenty clusters of the general formula [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P?)] (P-P? = chiral diphosphine of the ferrocene-based Walphos or Josiphos families) have been synthesised and characterised. The clusters have be
- Abdel-Magied, Ahmed F.,Doverbratt, Isa,Haukka, Matti,Nordlander, Ebbe,Raha, Arun K.,Rahaman, Ahibur,Richmond, Michael G.,Singh, Amrendra K.,Theibich, Yusuf
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p. 4244 - 4256
(2020/04/17)
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- Electrocatalytic asymmetric hydrogenation of α,β-unsaturated acids in a PEM reactor with cinchona-modified palladium catalysts
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We have developed an electrocatalytic asymmetric hydrogenation reaction using a proton-exchange membrane (PEM) reactor that employs a polymer electrolyte fuel cell and industrial electrolysis technologies. Reasonable enantioselectivities and excellent current efficiencies were obtained in the asymmetric hydrogenation of α-phenylcinnamic acid under mild conditions without adding a supporting electrolyte. The current density was crucial to achieving the improved results observed.
- Atobe, Mahito,Fukazawa, Atsushi,Hashimoto, Yasushi,Sato, Yasushi,Tanaka, Kenta
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- Effect of particle restructuring during reduction processes over polydopamine-supported Pd nanoparticles
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The effect of catalyst restructuring on the polydopamine-supported Pd catalyzed transfer hydrogenation of ethyl 4-nitrobenzoate and the catalytic hydrogenation of (E)-2-methyl-2-butenoic acid is reported. Transmission electron microscopy investigation of different catalyst pre-treatment and reaction conditions revealed high catalytic activity in both reactions unless drastic aggregation of the active metal occurred. In the transfer hydrogenation reaction aggregation was primarily dependent on the H-source used, while in the catalytic hydrogenation additives in combination with the reductive environment led to extensive Pd aggregation and thus decreased catalytic activity. The enantioselective hydrogenation of (E)-2-methyl-2-butenoic acid showed increased enantioselectivity and decreased conversion with increased particle size.
- Gazdag, Tamás,Baróthi, ádám,Juhász, Koppány Levente,Kunfi, Attila,Németh, Péter,Sápi, András,Kukovecz, ákos,Kónya, Zoltán,Szori, Kornél,London, Gábor
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p. 484 - 491
(2018/12/13)
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- Hydrogen/deuterium isotopic labeling study of enantioselective hydrogenation of (E)-2-Methyl-2-butenoic acid over a cinchonidine-modified Pd/C catalyst
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In the enantioselecitve hydrogenation of (E)-2-methyl-2butenoic acid (1) over a cinchonidine-modified Pd/C catalyst, the addition of hydrogen preferentially proceeds from the Re-Si enantioface of the C=C double bond of 1 to yield (S)-2methylbutanoic acid ((S)-3). Double bond migration of 1 takes place under the reaction conditions and is followed by immediate hydrogenation to yield 3 in a poor enantiomeric purity. Deuterium labeling experiments at 0.1 MPa and 1.9 MPa of D2verified the previous assumption of competitive double bond migration. The combination of isotopic labeling experiments and chiral analysis revealed that the double bond migration of 1 proceeds with the same enantiofacial differentiation as the hydrogenation of 1. Thus, interaction of 1 with cinchonidine adsorbed on the Pd surface may control the configuration of the double bond migration and the hydrogenation.
- Sugimura, Takashi,Tomatsuri, Satoshi,Fujita, Morifumi,Okamoto, Yasuaki
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p. 1737 - 1742
(2019/10/01)
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- Chemoenzymatic Cascade Synthesis of Optically Pure Alkanoic Acids by Using Engineered Arylmalonate Decarboxylase Variants
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Arylmalonate decarboxylase (AMDase) catalyzes the cofactor-free asymmetric decarboxylation of prochiral arylmalonic acids and produces the corresponding monoacids with rigorous R selectivity. Alteration of catalytic cysteine residues and of the hydrophobic environment in the active site by protein engineering has previously resulted in the generation of variants with opposite enantioselectivity and improved catalytic performance. The substrate spectrum of AMDase allows it to catalyze the asymmetric decarboxylation of small methylvinylmalonic acid derivatives, implying the possibility to produce short-chain 2-methylalkanoic acids with high optical purity after reduction of the nonactivated C=C double bond. Use of diimide as the reductant proved to be a simple strategy to avoid racemization of the stereocenter during reduction. The developed chemoenzymatic sequential cascade with use of R- and S-selective AMDase variants produced optically pure short-chain 2-methylalkanoic acids in moderate to full conversion and gave both enantiomers in excellent enantiopurity (up to 83 % isolated yield and 98 % ee).
- Enoki, Junichi,Mügge, Carolin,Tischler, Dirk,Miyamoto, Kenji,Kourist, Robert
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p. 5071 - 5076
(2019/03/17)
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- Convenient enzymatic resolution of (R,S)-2-methylbutyric acid catalyzed by immobilized lipases
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The application of several immobilized lipases has been explored in the enantioselective esterification of (R,S)-2-methylbutyric acid, an insect pheromone precursor. With the use of Candida antarctica B, using hexane as solvent, (R)-pentyl 2-methylbutyrat
- Mittersteiner, Mateus,Linshalm, Bruna Luiza,Vieira, Ana Paula Furlan,Brondani, Patrícia Bulegon,Scharf, Dilamara Riva,de Jesus, Paulo Cesar
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p. 106 - 111
(2017/11/14)
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- Pentasaccharide resin glycosides with multidrug resistance reversal activities from the seeds of: Pharbitis nil
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Resin glycosides are novel P-glycoprotein inhibitors. In order to evaluate their multidrug resistance (MDR) reversal activities, we isolated seven new resin glycosides, pharbitins A-G (1-7) from the seeds of Pharbitis nil. Their chemical structures were determined by extensive application of high resolution 2D NMR techniques, HRESIMS and chemical methods. Compounds 1-4 and 6 were evaluated for their MDR reversal activities in KB/VCR, A549/T and K562/ADR cells. Among them, compound 2 showed moderate MDR reversal activity in KB/VCR cells, and increased the cytotoxicity of vincristine by 2.2-fold when incorporated at 25 μM. A structure-activity relationship study revealed that substituting Rha′′ C-3 with a trans-cinnamoyl group improves the MDR reversal activity. Also, an intracellular Rh123 accumulation assay demonstrated that compound 2 could inhibit the function of P-gp.
- Li, Jun,Wang, Wen-Qiong,Tang, Shuai,Song, Wei-Bin,Huang, Min,Xuan, Li-Jiang
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supporting information
p. 52001 - 52009
(2017/11/22)
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- Hydrogenation of (E)-2-methyl-2-butenoic acid over cinchona-modified Pd catalyst in the presence of achiral amines: Solvent and modifier effect
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The effect of the solvent, modifier structure and concentration on the enantioselective hydrogenation of (E)-2-methyl-2-butenoic acid over Pd/Al 2O3 modified by cinchona alkaloids was influenced by the addition of achiral amines to t
- Makra, Zsolt,Szollosi, Gy?rgy
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p. 113 - 117
(2014/01/17)
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- Diastereomeric control of enantioselectivity: Evidence for metal cluster catalysis
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Enantioselective hydrogenation of tiglic acid effected by diastereomers of the general formula [(μ-H)2Ru3(μ3-S)(CO) 7(μ-P-P*)] (P-P* = chiral Walphos diphosphine ligand) strongly supports catalysis by intact Ru
- Abdel-Magied, Ahmed F.,Singh, Amrendra K.,Haukka, Matti,Richmond, Michael G.,Nordlander, Ebbe
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supporting information
p. 7705 - 7708
(2014/07/08)
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- Diterpenoid alkaloids and flavonoids from Delphinium trichophorum
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Five hetisane-type C20-diterpenoid alkaloids, trichodelphinines A-E, one delnudine-type C20-diterpenoid alkaloid, trichodelphinine F and three known flavonoids, quercetin, quercetin 3-O-β-d-glucopyranoside, and quercetin 3-O-β-d-glucopyranoside-7-O-α-l-arabinopyranoside, were isolated from whole plants of Delphinium trichophorum Franch. Their structures were elucidated on the basis of extensive spectroscopic analysis, including HSQC, HMBC, 1H-1H COSY, NOESY and X-ray crystallographic analysis, and from chemical evidence. The cytotoxic activities of the diterpenoid alkaloids were evaluated using the MTT method, and the IC 50 values of their cytotoxicity against A549 cancer cells ranged from 12.03 to 52.79 μM.2013 Elsevier Ltd. All rights reserved.
- Lin, Chao-Zhan,Zhao, Zhong-Xiang,Xie, Si-Min,Mao, Ju-Hua,Zhu, Chen-Chen,Li, Xiao-Hui,Bairi, Zeren-Dawa,Kangsa, Suolang-Qimei,Dun, Zhu,Xiong, Tian-Qin,Wu, Ai-Zhi
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- Enantioselective hydrogenation of α,β-unsaturated carboxylic acid over cinchonidine-modified Pd nanoparticles confined in carbon nanotubes
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We report the enantioselective hydrogenation of α,β-unsaturated acid catalyzed by Pd nanoparticles in carbon nanotubes (CNTs) taking the advantage of the channels as nanoreactors. The Pd nanocatalyst inside the channels of CNTs shows higher activity and e
- Guan, Zaihong,Lu, Shengmei,Li, Can
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- Palladium nanoparticle-graphene catalysts for asymmetric hydrogenation
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We report for the first time the application of palladium nanoparticle-graphene (Pd/Gn) catalysts in the asymmetric hydrogenation of aliphatic α,β-unsaturated carboxylic acids using cinchonidine as chiral modifier. Pd/Gns were prepared by deposition-preci
- Sz?ri, Korne?l,Puskás, Robert,Sz?ll?si, Gyo?rgy,Bertóti, Imre,Szépv?lgyi, János,Bartók, Mihály
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p. 539 - 546
(2013/07/11)
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- Enantioselective hydrogenation of α,β-unsaturated carboxylic acids on Pd nanocubes
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Pd nanocubes of 6-19 nm in size were synthesized using a seeded growth method and examined for enantioselective hydrogenation of α,β- unsaturated carboxylic acids. It was found that the Pd nanocubes had two types of active sites on the planes and at the edges, respectively. Small nanocubes having a higher edge/plane ratio were more active in enantioselective hydrogenation of α,β-unsaturated carboxylic acids, but afforded a lower enantioselectivity because their sharp edges could not offer stable adsorption of the chiral modifier and the reaction intermediates. In contrast, large nanocubes with a higher fraction of flat planes provided a higher enantioselectivity but a much lower activity.
- Chen, Chunhui,Zhan, Ensheng,Ta, Na,Li, Yong,Shen, Wenjie
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p. 2620 - 2626
(2013/09/24)
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- Achiral amine additives in the enantioselective hydrogenation of aliphatic α,β-unsaturated acids over cinchonidine-modified Pd/Al 2O3 catalyst
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The effect of the achiral amine additive structure was studied on the enantioselective hydrogenation of (E)-2-methyl-2-butenoic acid and (E)-2-methyl-2-hexenoic acid over Pd/Al2O3 catalyst modified by cinchonidine. It was found that
- Makra, Zsolt,Sz?ll?si, Gy?rgy,Bartók, Mihály
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experimental part
p. 56 - 61
(2012/03/10)
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- Efficient cluster-based catalysts for asymmetric hydrogenation of α-unsaturated carboxylic acids
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The new clusters [H4Ru4(CO)10(μ-1,2-P- P)], [H4Ru4(CO)10(1,1-P-P)] and [H 4Ru4(CO)11(P-P)] (P-P=chiral diphosphine of the ferrocene-based Josiphos or Walphos ligand families) have been synthesised and characterised. The crystal and molecular structures of eleven clusters reveal that the coordination modes of the diphosphine in the [H4Ru 4(CO)10(μ-1,2-P-P)] clusters are different for the Josiphos and the Walphos ligands. The Josiphos ligands bridge a metal-metal bond of the ruthenium tetrahedron in the "conventional" manner, that is, with both phosphine moieties coordinated in equatorial positions relative to a triangular face of the tetrahedron, whereas the phosphine moieties of the Walphos ligands coordinate in one axial and one equatorial position. The differences in the ligand size and the coordination mode between the two types of ligands appear to be reflected in a relative propensity for isomerisation; in solution, the [H4Ru4(CO)10(1,1-Walphos)] clusters isomerise to the corresponding [H4Ru4(CO) 10(μ-1,2-Walphos)] clusters, whereas the Josiphos-containing clusters show no tendency to isomerisation in solution. The clusters have been tested as catalysts for asymmetric hydrogenation of four prochiral α-unsaturated carboxylic acids and the prochiral methyl ester (E)-methyl 2-methylbut-2-enoate. High conversion rates (>94 %) and selectivities of product formation were observed for almost all catalysts/catalyst precursors. The observed enantioselectivities were low or nonexistent for the Josiphos-containing clusters and catalyst (cluster) recovery was low, suggesting that cluster fragmentation takes place. On the other hand, excellent conversion rates (99-100 %), product selectivities (99-100 % in most cases) and good enantioselectivities, reaching 90 % enantiomeric excess (ee) in certain cases, were observed for the Walphos-containing clusters, and the clusters could be recovered in good yield after completed catalysis. Results from high-pressure NMR and IR studies, catalyst poisoning tests and comparison of catalytic properties of two [H4Ru4(CO)10(μ-1,2-P-P)] clusters (P-P=Walphos ligands) with the analogous mononuclear catalysts [Ru(P-P)(carboxylato)2] suggest that these clusters may be the active catalytic species, or direct precursors of an active catalytic cluster species. Copyright
- Moberg, Viktor,Duquesne, Robin,Roehrs, Oliver,Nachtigall, Jonny,Nordlander, Ebbe,Contaldi, Simone,Monari, Magda,Damoense, Llewellyn,Green, Michael,Hutton, Alan T.,Santelia, Daniela,Haukka, Matti
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p. 12458 - 12478,21
(2020/08/24)
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- Is amine addition vital for highly enantioselective hydrogenation of α,β-unsaturated carboxylic acid over cinchonidine-modified palladium?
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Benzylamine (BA) is a commonly employed additive for the hydrogenation of α,β-unsaturated acids over the cinchonidine-modified palladium catalyst, but the BA addition effects largely depend on the reaction solvent. In toluene, BA is not required to obtain the high enantioselectivity. Quicker desorption of the product due to weaker acidity in toluene than in a commonly used wet dioxane reasonably explains both the kinetic properties and the product selectivities.
- Kim, Tae Yeon,Sugimura, Takashi
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experimental part
p. 58 - 62
(2010/11/16)
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- Structural requirements for substrate in highly enantioselective hydrogenation over the cinchonidine-modified Pd/C
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Relationship between substrate structure and enantioselectivity is studied for the asymmetric hydrogenation of 42 different (E)-α, β-disubstituted acrylic acids (propenoic acids) over cinchonidine-modified Pd/C. The β-phenyl group is indispensable for high enantioselectivity of α-phenylcinnamic acid (2,3-diphenylpropenoic acid, 81% ee), and substitution on this group affects markedly the selectivity. The high ee up to 92% was achieved by the β - p-alkoxyphenyl substitution, and the selectivity is ascribed mainly to stronger interaction of the substrate with the chiral modifier on the catalyst surface. In contrast, substitution on the α-phenyl group does not affect notably the enantioselectivity (80-82% ee) or even the α-phenyl group itself is not indispensable but replaceable with a properly bulky group for the high enantioselectivity.
- Sugimura, Takashi,Uchida, Takayuki,Watanabe, Junya,Kubota, Takeshi,Okamoto, Yasuaki,Misaki, Tomonori,Okuyama, Tadashi
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experimental part
p. 57 - 64
(2009/06/17)
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- Intrapilosins I-VII, pentasaccharides from the seeds of Ipomoea intrapilosa
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Purification of a CHCl3-soluble extract from seeds of the Mexican medicinal arborescent morning glory, Ipomoea intrapilosa, by means of preparative-scale recycling HPLC, yielded seven new resin glycosides, intrapilosins I-VII (1-7). Their structures were established through the interpretation of their NMR spectroscopic and FABMS data. All pentasaccharides were found to be macrolactones of the known operculinic acid A with different fatty acids esterifying the same positions: C-2 on the second rhamnose unit and C-3 and C-4 on the third rhamnose moiety. The lactonization site of the aglycon could be placed at C-2 of the second saccharide. The fatty acid components of 1-7 were identified as (+)-(2S)-methylbutanoic, octanoic (caprylic), dodecanoic (lauric), and trans-cinnamic. The less common (-)-(2R)-methylbutanoic acid was also isolated as one of the saponification-liberated residues from intrapilosin IV (4). The presence of the (2R)- and (2S)-methylbutanoyl enantiomers bonded to the same oligosaccharide core in intrapilosins IV (4) and V (5) represents an example of diastereoisomerism due to a chiral esterifying moiety in the resin glycoside mixtures of a morning glory species.
- Bah, Moustapha,Cherigo, Lilia,Cardoso Taketa, Alexandre T.,Fragoso-Serrano, Mabel,Hammond, Gerald B.,Pereda-Miranda, Rogelio
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p. 1153 - 1157
(2008/02/13)
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- Highly efficient asymmetric hydrogenation of α,β-unsaturated carboxylic acids catalyzed by ruthenium(II)-dipyridylphosphine complexes
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Two types of catalysts [RuL(benzene)Cl]Cl and Ru(OCOCH3) 2L with the dipyridylphosphine ligands P-Phos and Xyl-P-Phos were applied in the asymmetric hydrogenation of α,β-unsaturated carboxylic acids. The cationic complexes [RuL(benzene)Cl]Cl were found to be superior to the corresponding neutral complex Ru(OCOCH3)2L in this type of reactions. The catalysts exhibited excellent activities and enantioselectivities (up to 97% ee) in the asymmetric hydrogenation.
- Qiu, Liqin,Li, Yue-Ming,Kwong, Fuk Yee,Yu, Wing-Yiu,Fan, Qing-Hua,Chan, Albert S. C.
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p. 517 - 520
(2008/02/08)
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- Asymmetric hydrogenation of α,β-unsaturated carboxylic acids catalyzed by ruthenium(II) complexes of spirobifluorene diphosphine (SFDP) ligands
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The ruthenium diacetate complexes ligated by chiral spirobifluorene diphosphines (SFDP) were very effective catalysts for the asymmetric hydrogenation of tiglic acid derivatives and α-methylcinnamic acid derivatives with high activities and excellent enantioselectivities (up to 98% ee). The α-aryloxybutenoic acids can also be hydrogenated by these catalysts to provide the corresponding saturated α-aryloxybutanoic acids in high yields (89-93%) and enantioselectivities (up to 95% ee). In this reaction, the SFDP ligand with para-methyl groups on the P-phenyl rings gave the best results.
- Cheng, Xu,Xie, Jian-Hua,Li, Sheng,Zhou, Qi-Lin
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p. 1271 - 1276
(2007/10/03)
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- Achiral ligands dramatically enhance rate and enantioselectivity in the Rh/phosphoramidite-catalyzed hydrogenation of α,β-disubstituted unsaturated acids
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(Chemical Equation Presented) Mixing it up: A catalytic system based on a mixed-ligand approach has been developed for the rhodium-catalyzed asymmetric hydrogenation of cinnamic acid derivatives (see scheme, cod = cycloocta-1,5-diene). It is the first time that a catalyst complex based on a heterocombination of a chiral and an achiral monodentate ligand gives dramatically higher enantioselectivity (up to 99%) than any of the corresponding homocomplexes.
- Hoen, Rob,Boogers, Jeroen A. F.,Bernsmann, Heiko,Minnaard, Adriaan J.,Meetsma, Auke,Tiemersma-Wegman, Theodora D.,De Vries, Andre H. M.,De Vries, Johannes G.,Feringa, Ben L.
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p. 4209 - 4212
(2007/10/03)
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- Enantiomeric partitioning using fluorous biphase methodology for lipase-mediated (trans)esterifications
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Lipase-catalysed (trans)esterification reactions in homogenous perfluorocarbon-hydrocarbon solvents enabled direct enantiomeric partitioning (up to 95% ee) of the products by liquid-liquid separation.
- Beier, Petr,O'Hagan, David
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p. 1680 - 1681
(2007/10/03)
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- Hydrogen pressure dependence in enantioselective hydrogenation of α,β-unsaturated acids with cinchonidine-modified Pd/TiO2 catalyst
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The enantioselectivity in the hydrogenation of (E)-2,3-diphenyl-2-propenoic acid with a cinchonidine-modified 5wt%Pd/TiO2 catalyst decreases with increasing pressure of hydrogen up to 5 MPa contrary to the tendency observed in the hydrogenation of aliphatic acids, probably because of the difference in the adsorption strength of the substrates on both modified and unmodified sites.
- Nitta
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p. 1971 - 1972
(2007/10/03)
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- 2,2',5,5'-tetramethyl-4,4'-bis(diphenylphoshino)-3,3'-bithiophene: A new, very efficient, easily accessible, chiral biheteroaromatic ligand for homogeneous stereoselective catalysis
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The four-step straightforward synthesis of enantiopure (+)- and (-)- 2,2',5,5'-tetramethyl-4,4'-bis(diphenylphoshino)-3,3'-bithiophene (tetraMe- BITIOP), anew C2-symmetry chelating ligand for transition metals, is described, starting from 2,5-dimethylthiophene. The complexes of this electron-rich diphosphine with Ru(II) and Rh(I) were used as catalysts in some homogeneous hydrogenation reactions of prostereogenic carbonyl functions of α- and β-ketoesters, of prostereogenic carbon-carbon double bonds of substituted acrylic acids, and of N-acetylenamino acids. The enantiomeric excesses were found to be excellent in all the experiments and comparable with the best results reported in the literature for the same reactions, carried out under similar experimental conditions, with the metal complexes of the most popular chiral diphosphine ligands as catalysts.
- Benincori, Tiziana,Cesarotti, Edoardo,Piccolo, Oreste,Sannicolo, Franco
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p. 2043 - 2047
(2007/10/03)
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- Heterogeneous catalytic hydrogenation of olefinic substrates by poly-NAP
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With our previously described poly-NAP, various olefinic substrates were reduced with selectivities comparable to those obtained by BINAP. For substrates which contained a methyl ester, the selectivities were higher than those observed for their carboxylic acid analogues. (C) 2000 Elsevier Science Ltd.
- Ter Halle, Rob,Schulz, Emmanuelle,Spagnol, Michel,Lemaire, Marc
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p. 3323 - 3326
(2007/10/03)
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- Synthesis and evaluation of a new steroidal BINAP type phosphine
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The short and high yielding synthesis of a new cis-configured bissteroidal phosphine 7 is reported. The comparison of these new phosphines as ligands in ruthenium-based hydrogenation catalysts with the previously synthesized diastereomeric trans-configured phosphines 20 shows that the steroid backbone exerts only a minor influence on the enantioselection of the ruthenium catalysts and confirms that the bissteroidal phosphines behave as 'pseudo'-enantiomers in spite of their diastereomeric nature. Evidence is presented that the mode of catalyst preparation, i.e. catalyst structure, is the crucial reaction parameter which mainly determines the enantiomeric excess of the hydrogenation products. (C) 2000 Elsevier Science Ltd.
- Enev,Harre,Nickisch,Schneider,Mohr
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p. 1767 - 1779
(2007/10/03)
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- The role of functionalized phosphines in the hydrogenation of carboxylic acids in the presence of phosphine substituted hydrido ruthenium complexes
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Hydrido ruthenium carbonyl complexes substituted by functionalized phosphines such as H4Ru4(CO)8[P(CH2OCOR) 3]4 have been synthesized and tested as catalysts in the hydrogenation of carboxylic acids. These complexes are more active than those reported previously, containing trialkyl- or triarylphosphines. On the basis of their behavior, their different activity has been explained in terms of an involvement of the phosphine ligand in the catalytic cycle. The ester group present in the phosphine P(CH2OCOR)3 is hydrogenated to produce an alcohol (RCH2OH) and a P(CH2OH) group which, in turn, reacts with the free acid present in solution to restore the P(CH2OCOR) group. This hypothesis has been confirmed by the reactivity of the possible intermediate H4Ru4(CO)8[P(CH2OH) 3]4 with acetic acid. Another support to this statement is the almost equal catalytic activity, displayed by H4Ru4(CO)8[P(CH2OCOR) 3]4 complexes, whatever the R group present, in the phosphine ligand, in the hydrogenation of carboxylic acids. These complexes, on the other hand, are less active than the corresponding tributylphosphine substituted ones in the hydrogenation of alkenes and ketones. Finally when the phosphine ligand is P(CH2CH2COOCH3)3 the ester group is not reduced and consequently the catalytic activity of this complex in the hydrogenation of carboxylic acids is very low.
- Salvini, Antonella,Frediani, Piero,Bianchi, Mario,Piacenti, Franco,Pistolesi, Leonardo,Rosi, Luca
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p. 218 - 228
(2007/10/03)
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- Enantioselective ruthenium-mediated hydrogenation: Developments and applications
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A general preparation of chiral ruthenium(II) catalysts and the homogeneous enantioselective hydrogenation of prochiral olefins and keto groups are presented. Some applications to the synthesis of biologically active compounds are reported.
- Ratovelomanana-Vidal, Virginie,Genet, Jean-Pierre
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p. 163 - 171
(2007/10/03)
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- Application of [Ru((R)-BINAP)(MeCN)(1-3:5,6-η-C8H11)](BF4) as a catalyst precursor for enantioselective hydrogenations
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A catalyst system employing [Ru((R)-BINAP)(MeCN)(1-3:5,6-η- C8H11)](BF4) as catalyst precursor was evaluated using the enantioselective hydrogenations of tiglic acid, α-acetamidocinnamic acid, itaconic acid, methyl tiglate, dimethyl itaconate, geraniol, ethyl acetoacetate, and dimethyl oxaloacetate as a series of typical substrates. Acetone and MeOH were used as model aprotic and protic solvents, respectively. The hydrogenation of substrates containing an α,β-unsaturated carboxylic acid functionality required stoichiometric quantities of NEt3 to occur at reasonable rates in acetone solution, while in MeOH solution it did not. The enantioselectivities were typically higher in acetone than in MeOH. This catalyst system is among the more enantioselective ruthenium-BINAP type systems reported for the catalytic hydrogenation of substrates containing an α,β-unsaturated acid or ester functionality. The enantioselectivities for the hydrogenation of ketones ranged from poor (15%) to moderate (74%). 1,4- Dicarboxylate substrates with the prochiral olefin or ketone at the 2- position were all hydrogenated in good to high ee with the same enantioface selectivity both with our system and other catalysts reported in the literature. This raised the possibility that these substrates were hydrogenated through intermediates with similar structural features.
- Daley, Christopher J.A.,Wiles, Jason A.,Bergens, Steven H.
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p. 1447 - 1456
(2007/10/03)
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- Asymmetric hydrogenation of acrylic acid derivatives by novel chiral rhodium-phosphinediamine complex catalysts by selective ligation between two amino units of the ligand and electrostatic interaction
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The novel chiral phosphinediamine ligand (PN2) having two amino units has been readily prepared from (S)-1-phenylethylamine derivatives and dichlorophosphine. In the hydrogenation of acrylic acids by a rhodium-PN2 catalyst, high enantioselectivities were achieved by the effective chiral field formed through selective P-N chelation and electrostatic interaction between the amino unit of the ligand and the carboxy unit of the substrate.
- Yamada, Issaku,Ohkouchi, Munetaka,Yamaguchi, Motowo,Yamagishi, Takamichi
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p. 1869 - 1873
(2007/10/03)
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- Asymmetric hydrogenation of α,β-unsaturated carboxylic acids in supercritical carbon dioxide
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Hydrogenation of tiglic acid in supercritical CO2 catalyzed by a chiral H8-BINAP-Ru(II) complex proceeds cleanly with cis stereochemistry to afford 2-methylbutanoic acid in up to 89% ee and over 99% yield.
- Xiao, Jianliang,Nefkens, Sylvia C. A.,Jessop, Philip G.,Ikariya, Takao,Noyori, Ryoji
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p. 2813 - 2816
(2007/10/03)
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- New Class of Chiral Diphosphine Ligands for Highly Efficient Transition Metal-Catalyzed Stereoselective Reactions: The Bis(diphenylphosphino) Five-membered Biheteroaryls
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The synthesis and application of three examples of a new class of chiral (C2) atropisomeric diphosphines characterized by two interconnected five-membered heteroaromatic rings, with hindered rotation around the interanular bond, are described.Optically pure (+)- and (-)-2,2'-bis(diphenylphosphino)-4,4',6,6'-tetramethyl-3,3'-bibenzothiophene (tetraMe-bitianp) (1a) and the parent unsubstituted system (+)- and (-)-bitianp (1b) were synthesized.They were found to be optically stable at 100 deg C and were successfully employed as ligands in the Ru(II)-catalyzed hydrogenation of α- and β-oxo esters to the corresponding α- and β-hydroxy esters and in the hydrogenation of olefinic substrates.The optical and chemical yields were comparable with those reported for the same Ru(II)-binap-catalyzed reactions carried out under the same experimental conditions.The 2,2'-bis(diphenylphosphino)-3,3'-bibenzofuran (1c), the oxygenated analogue of bitianp, was found to be configurationally unstable at room temperature.Complete structural X-ray elucidation of the Pd complexes of 1a-c is reported.The advantages of these biheteroaromatic ligands over the classical biaryl systems are discussed.
- Benincori, Tiziana,Brenna, Elisabetta,Sannicolo, Franco,Trimarco, Licia,Antognazza, Patrizia,et al.
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p. 6244 - 6251
(2007/10/03)
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- A novel chiral phosphinediamine ligand and asymmetric hydrogenation of acrylic acid derivatives
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A novel chiral phosphinediamine ligand (PN2) was prepared from (S)-1-phenylethylamine and dichloroisopropylphosphine. The rhodium-PN2 catalyst utilizing selective ligation of the amino unit and electrostatic interaction between the ligand and a substrate gave high enantioselectivities up to 92% ee in asymmetric hydrogenations of acrylic acid derivatives.
- Yamada, Issaku,Yamaguchi, Motowo,Yamagishi, Takamichi
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p. 3339 - 3342
(2007/10/03)
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- ENANTIOSELECTIVE HYDROGENATION REACTIONS WITH A FULL SET OF PREFORMED AND PREPARED IN SITU CHIRAL DIPHOSPHINE-RUTHENIUM (II) CATALYSTS
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The new class of 2-methylallyl ruthenium chiral diphosphines 1 are efficient in asymmetric hydrogenation of α,β unsaturated acids and allylic alcohols.The related chiral halogen-containing ruthenium catalysts 2 are prepared from 1 or in situ from (COD)Ru(η3-(CH2)2CHCH3)2 by ligand exchange with the chelating diphosphine followed by protonation (HX) in acetone.This procedure allows rapid screening of chiral phosphines, such as Diop, Chiraphos, Cbd, Bppm, Binap, β-glucophos, Biphemp, MeO-Biphep, Me-Duphos, in ruthenium mediated hydrogenations of prochiral substrates.A high efficiency is displayed by Ru-catalysts having atropisomeric ligands (e.e. up to 99percent), and a C2 symmetric bis(phospholane) has also emerged as a valuable ligand (Me-Duphos, e.e. up to 87percent not optimized).Asymmetric hydrogenation of β-keto esters can be conducted under quite mild conditions (4 atm. of H2, 50 deg C, e.e. up to 99percent), β-keto esters having a disubstituted double bond are also hydrogenated chemoselectively to unsaturated chiral alcohols under controlled conditions with excellent optical purities.
- Genet, J. P.,Pinel, C.,Ratovelomanana-Vidal, V.,Mallart, S.,Pfister, X.,et al.
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p. 675 - 690
(2007/10/02)
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- Cationic BINAP-Ru(II) Halide Complexes: Highly Efficient Catalysts for Stereoselective Asymmetric Hydrogenation of α- and β-Functionalized Ketones
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Cationic ruthenium-BINAP complexes 5, 7, and 10 of the formula Y, where X = Cl, Br, I; Y = Cl, Br, I, BF4, B(C6H5)4; arene = benzene, p-cymene, ethyl benzoate, and their enantiomers have been prepared by the reaction of arene-ruthenium halide complexes 4, 6, and 9 with (S)-BINAP or (R)-BINAP.Structures of the complexes were established by spectroscopy, conductivity, and a single-crystal X-ray analysis (5d: orthorhombic, P21212; a=20.141(2) Angstroem, b=18.504(1) Angstroem, c=12.241(1) Angstroem, V=4562.0(7) Angstroem3, Z=4, R=0.078 for unique 4177 reflections).BINAP derivatives with various substituents at the para and meta positions of four phenyl rings on phosphorus atoms and their cationic Ru(II) complexes have also been synthesized.These BINAP-Ru(II) complexes have been used as catalysts for the asymmetric hydrogenation of various unsaturated organic compounds such as α- and β-keto esters, allylic alcohols, and α,β-unsaturated carboxylic acids in excellent diastereo- and/or enantioselectivities.Catalytic activities and stereoselectivities depend highly on reaction conditions such as solvent, temperature, and additives.Variation of halogen ligands bound to ruthenium atom and substituents on four phenyl rings of BINAP also have exerted remarkable effects on the efficiency of the catalysis.Asymmetric hydrogenation of methyl (+/-)-2-(benzamidomethyl)-3-oxobutanoate catalyzed by the species derived from 9c and 3,5-(t-Bu)2-BINAP afforded the corresponding syn-(2S,3R)-17 in 98percent de and 99percent ee.
- Mashima, Kazushi,Kusano, Koh-hei,Sato, Naomasa,Matsumura, Yoh-ichi,Nozaki, Kyoko,et al.
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p. 3064 - 3076
(2007/10/02)
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- Optically active alkylvinylpyridines: Synthesis of (±)-(S)-6-(1-methylpropyl)-2-vinylpyridine
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A generalizable procedure for the preparation of optically active 6-alkyl-2-vinylpyridines from chiral 2-alkylpyridines without loss of optical purity is reported.
- Chelucci
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p. 2645 - 2651
(2007/10/02)
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- Enantiomerically pure dihydropyrimidinones as reagents and auxiliaries for asymmetric synthesis
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We report herein full experimental details of the synthesis, structure, and reactivity of (R)- and (S)-2-tert-butyl-l-carbomethoxy-2,3-dihydropyrimidin-4(lH)-one (1). The synthesis employs asparagine as the starting material and provides 1 in 55% yield without the need for Chromatographic purification. The structure of 1, as determined by X-ray crystallographic analysis, demonstrates significant pyramidalization at the C4 (carbonyl) and N1 centers, with little evidence of conjugation of Nl with the αβ,-unsaturated (vinylogous urea) system. In contrast, compound 11 [2-tert-butyl-3-((S)-O-methylmandeloyl)-2,3-dihydropyrimidin-4(lH)-one] shows strong coupling of Nl to the αβ,-unsaturated system, as evidenced by changes in bond lengths and torsional angles. Compound 1 has proven useful as a reagent for the synthesis of enantiomerically pure β-aryl-β-amino acids. The key step in this protocol is the palladium-catalyzed conjugate addition of aryl iodides to 1. Evidence is presented to support a mechanism for this reaction that involves an unprecedented transannular hydride transfer into the palladium coordination sphere. In additional experiments, 1 has been employed as an auxiliary for the synthesis of enantiomerically pure α-substituted carboxylic acids. The crystalline properties of 1 and many of its derivatives allow for simplified purification procedures to be utilized.
- Chu, Kent S.,Negrete, George R.,Konopebki, Joseph P.,Lakner, Frederick J.,Woo, Nam-Tae,Olmstead, Marilyn M.
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p. 1800 - 1812
(2007/10/02)
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- The origin of the enantioselection in the ruthenium(II)-catalyzed asymmetric hydrogenation of α,β-unsaturated carboxylic acid
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Using our chiral atropisomeric bisphosphines ruthenium(II) complexes, asymmetric hydrogenations of tiglic acid and its isomer were carried out. A possible enantioselective mechanism was considered on the basis of their different results on hydrogenation pressure effects.
- Yoshikawa,Murata,Yamamoto,Inoguchi,Achiwa
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p. 1072 - 1074
(2007/10/02)
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- Asymmetric hydrogenation of prochiral carboxylic acids and functionalized carbonyl compounds catalysed by ruthenium(II)-binap complexes with aryl nitriles (binap=(R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl)
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Complexes RuCl2(ArCN)2(binap), II (binap=(R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl; ArCN=benzonitrile, a; 2-furancarbonitrile, b; pentafluorobenzonitrile, c) were prepared, and their solution properties were investigated by 31P NMR measurements.The catalytic aactivities and enantioselectivities for IIa-c catalysed hydrogenation of some prochiral acids were very similar to those provided by Ru2Cl4(binap)2(NEt3), I.In the hydrogenation of β-functionalized carbonyl compounds, however, IIa-c showed considerably lower activities and/or selectivities, compared with complex I.The differences in IIa-c catalysed reactions are discussed in relation to the coordinating abilities of ArCN in II.
- Shao, Liming,Takeuchi, Kasumi,Ikemoto, Makoto,Kawai, Toshiyasu,Ogasawara, Masamichi,et al.
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p. 133 - 147
(2007/10/02)
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- Asymmetric hydrogenation of prochiral carboxylic acids catalyzed by the five-coordinate ruthenium(II)-hydride complex PF6 (binap = (R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl)
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The five-coordinate complex PF6 (1, binap = (R)- or (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) has been found to have sufficient catalytic activity for asymmetric hydrogenation of itaconic acid and other prochiral carboxylic acids under mild conditions.The catalytic hydrogenation of itaconic acid by I was examined under a variety of conditions, and the addition of triethylamine was found to effect high enantioselectivities (above 90percent ee). 1H and 31 P NMR examinations of reaction mixtures of I and itaconic acid under conditions similar to the hydrogenation suggested the formation of ruthenium species containing one binap chelate.
- Saburi, Masahiko,Takeuchi, Hiroshi,Ogasawara, Masamichi,Tsukahara, Touru,Ishii, Youichi,et al.
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p. 155 - 167
(2007/10/02)
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- General synthesis of novel chiral ruthenium catalysts and their use in asymmetric hydrogenation
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The first general synthesis of mononuclear hexacoordinate chiral ruthenium-complexes is presented. Four chiral ruthenium(II)(2-methylallyl)2 complexes containing Diop, Chiraphos, Norphos, and Binap were prepared in 50-71% yield under mild conditions, and were found to be effective for asymmetric hydrogenation of unsaturated carboxylic acids to give the corresponding saturated derivatives attaining 90% optical purity.
- Genet,Mallart,Pinel,Juge,Laffitte
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- Synthesis of axially dissymmetric biphenylbisphosphine ligands, BIMOPs and asymmetric hydrogenations of β-keto ester and α,β-unsaturated carboxylic acid catalyzed by their ruthenium (II) complexes
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Axially dissymmetric biphenylbisphosphine ligands, BIMOP (1a) and p-MeO-BIMOP (1b) have been newly designed and prepared. The ruthenium (II) complexes of (R)-1a and 1b proved to be excellent catalysts in asymmetric hydrogenations of methyl 3-oxobutanoate and tiglic acid affording (R)-methyl 3-hydroxybutanoate of 95-99 % ee and (R)-2-methylbutyric acid of 86-91 % ee, respectively.
- Yamamoto,Murata,Morimoto,Achiwa
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p. 1085 - 1087
(2007/10/02)
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- Enantioselective Catalytic Transfer Hydrogenation of α,β-Unsaturated Carboxylic Acids with Formates Catalyzed by Novel Ruthenium Phosphine Complexes
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Hydrogen transfer from the formic acid/triethylamine (5:2) azeotrope to α,β-unsaturated carboxylic acids is effectively catalyzed by ruthenium complexes of general formula 3-C3H5)(diphosphine).If a chiral diphosphine is employed, the saturated acids are obtained in up to 93percent ee, the most active and selective catalyst being formed with BINAP.
- Brown, John M.,Brunner, Henri,Leitner, Walter,Rose, Michael
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p. 331 - 334
(2007/10/02)
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- Process for producing optically active carboxylic acid
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A process for producing an optically active carboxylic acid represented by formula (I): STR1 wherein R1, and R2, and R3 each represents a hydrogen atom, an alkyl group, an alkenyl group, or a phenyl or naphthyl group which may have a substituent, provided that all of R1, R2, and R3 are not simultaneously a hydrogen atom; when R1 and R2 are simultaneously a hydrogen atom, then R3 is not a methyl group; and that when R3 is a hydrogen atom, then R1 and R2 are each a group other then a hydrogen atom, is disclosed, comprising asymmetrically hydrogenating an α,β-unsaturated carboxylic acid represented by formula (II): STR2 wherein R1, R2, and R3 are the same as defined above, in the presence of a ruthenium-optically active phosphine complex as a catalyst. According to the process of the invention, the desired optically active carboxylic acids which can be widely used as raw materials for synthesizing various useful compounds, for example, as intermediates for synthesizing physiologically active substances of natural materials and also as liquid crystal materials can be industrially advantageously produced.
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- Asymmetric Hydrogenation of Unsaturated Carboxylic Acids Catalyzed by BINAP-Ruthenium(II) Complexes
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Homogeneous hydrogenation of α,β- or β,γ-unsaturated carboxylic acids in the presence of a catalytic amount of Ru(OCOCH3)2 affords the corresponding saturated products in high enantiomeric excesses and in quantitative yields.The new hydrogenation has been applied to the asymmetric synthesis of (S)-naproxen, a 1β-methylcarbapenem precursor, and some methylated γ- and δ-lactones
- Ohta, Tetsuo,Takaya, Hidemasa,Kitamura, Masato,Nagai, Katsunori,Noyori, Ryoji
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p. 3174 - 3176
(2007/10/02)
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- Homogeneous Asymmetric Hydrogenation Using a Chiral Phosphinite Derivative of Carbohydrates as Ligand
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Diphenylphosphinite derivatives of sugars were conveniently synthesized by the reaction of diphenylphosphinous chloride-triethylamine with sugar derivatives.Homogeneous asymmetric hydrogenations of several prochiral olefins, i.e., (Z)-α-acetylaminocinnamic acid, (Z)-α-benzoylaminocinnamic acid, itaconic acid, tiglic acid, and their esters, were carried out using rhodium(I) catalysts with the tervalent chiral phosphorus derivative of sugars.The highest optical yields for all the prochiral substrates investigated were obtained when di-μ-chloro-bis(cyclooctadiene)dirhodium(I) and methyl 2,3-O-isopropylidene-4-O-(diphenylphosphino)-α-L-rhamnopyranoside were used.
- Yamashita, Mitsuji,Kobayashi, Mineaki,Sugiura, Motoyuki,Tsunekawa, Kenji,Oshikawa, Tatsuo,et al.
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p. 175 - 178
(2007/10/02)
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- ASYMMETRIC SYNTHESIS BY CHIRAL RUTHENIUM COMPLEXES. XI. ASYMMETRIC HYDROGENATION OF TIGLIC ACID IN THE PRESENCE OF PHOSPHINE SUBSTITUTED RUTHENIUM CARBONYL CARBOXYLATES
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The enantioface-discriminating hydrogenation of tiglic acid in the presence of (-)-DIOP substituted carbonyl carboxylato complexes of ruthenium has been investigated in order to identify the factors affecting the stereoselectivity of this reaction.The carboxylato ligand present in the catalytic intermediate does not seem to make a significant contribution to the stereoselectivity of this process.The stereoselectivity seems to be associated with the presence of the optically active phosphine.The catalytic system develops during the reaction through intermediates having a higher enantioface-discriminating activity than the initial and the final ruthenium complexes.
- Matteoli, Ugo,Menchi, Gloria,Frediani, Piero,Bianchi, Mario,Piacenti, Franco
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p. 281 - 292
(2007/10/02)
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- Asymmetric Synthesis of 2-Alkylalkanoic Acids via Alkylation of Chiral Amide Anions
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Acylation of (S)-proline methyl ester (2) gave amide ester 3 (R1=alkyl), which on reaction with methylmagnesium iodide furnished the tertiary alcohol 4.Alkylation of the dianion from this yielded mainly one diastereomer of the amide 5, which on acid hydrolysis gave the chiral 2-alkylalkanoic acid 6 in 75-90 percent e.e. and 55-82 percent chemical yield from the hydroxyamide 4.The latter compound could be recovered from the hydrolysate with preserved optical purity via acylation without isolation of the tertiary prolinol 7.The diastereomeric mixture of amides 5' and 5" could be separated by column chromatography leading to the acid 6 in very high optical purity.
- Guoqiang, Lin,Hjalmarsson, Mats,Hoegberg, Hans-Erik,Jernstedt, Karen,Norin, Torbjoern
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p. 795 - 802
(2007/10/02)
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