- Catalytic enantioselective borohydride reduction of Ortho-fluorinated benzophenones
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In the presence of the optically active ketoiminatocobalt(II) complexes, the enantioselective borohydride reduction of benzophenones was successfully completed. The fluorine atom on the ortho position of the benzophenone and aryl ketones proved effective for obtaining high enantioselectivities. The combined use of modified lithium borohydride afforded the corresponding benzhydrols and arylcarbinols in high yield and high enantioselectivity (88-96% ee).
- Kokura, Ai,Tanaka, Saiko,Ikeno, Taketo,Yamada, Tohru
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- AlIII-calix[4]arene catalysts for asymmetric Meerwein-Ponndorf-Verley reduction
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Chiral AlIII-calixarene complexes were investigated as catalysts for the asymmetric Meerwein-Ponndorf-Verley (MPV) reduction reaction when using chiral and achiral secondary alcohols as reductants. The most enantioselective catalyst consisted o
- Nandi, Partha,Solovyov, Andrew,Okrut, Alexander,Katz, Alexander
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- Asymmetric Transfer Hydrogenation of Diaryl Ketones with Ethanol Catalyzed by Chiral NCP Pincer Iridium Complexes
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The use of a chiral (NCP)Ir complex as the precatalyst allowed for the discovery of asymmetric transfer hydrogenation of diaryl ketones with ethanol as the hydrogen source and solvent. This reaction was applicable to various ortho-substituted diaryl keontes, affording benzhydrols in good yields and enantioselectivities. This protocol could be carried out in a gram scale under mild reaction conditions. The utility of the catalytic system was highlighted by the synthesis of the key precursor of (S)-neobenodine.
- Huang, Zheng,Liu, Guixia,Qian, Lu,Tang, Xixia,Wang, Yulei
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- Visible-Light-Driven Catalytic Deracemization of Secondary Alcohols
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Deracemization of racemic chiral compounds is an attractive approach in asymmetric synthesis, but its development has been hindered by energetic and kinetic challenges. Here we describe a catalytic deracemization method for secondary benzylic alcohols which are important synthetic intermediates and end products for many industries. Driven by visible light only, this method is based on sequential photochemical dehydrogenation followed by enantioselective thermal hydrogenation. The combination of a heterogeneous dehydrogenation photocatalyst and a chiral molecular hydrogenation catalyst is essential to ensure two distinct pathways for the forward and reverse reactions. These reactions convert a large number of racemic aryl alkyl alcohols into their enantiomerically enriched forms in good yields and enantioselectivities.
- Hu, Xile,Zhang, Zhikun
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supporting information
p. 22833 - 22838
(2021/09/09)
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- Method for synthesizing chiral secondary alcohol compound
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The invention discloses a method for synthesizing a chiral secondary alcohol compound. The method comprises the following step of: reacting a ketone compound in an aprotic organic solvent at room temperature and inert gas atmosphere under the action of a chiral cobalt catalyst and an activating agent by taking a combination of bis(pinacolato)diboron and alcohol or water as a reducing agent to obtain the chiral secondary alcohol compound. According to the method disclosed by the invention, a combination of pinacol diborate and alcohol or water which are cheap, stable and easy to obtain is taken as a reducing agent, and a ketone compound is efficiently reduced to synthesize a corresponding chiral secondary alcohol compound in an aprotic organic solvent under the action of a chiral cobalt catalyst; in a chiral cobalt catalyst adopted by the method, when a chiral ligand is PAOR, an activating agent is NaBHEt3 or NaOtBu and an adopted raw material is aromatic ketone, the yield is 80% or above, and the optical purity is 90% or above; and when the adopted raw material is alkane ketone, the yield can reach 70% or above, and the optical purity can reach 80% or above.
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Paragraph 0038-0043; 0099-0103
(2021/05/29)
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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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- Highly Enantioselective Cobalt-Catalyzed Hydroboration of Diaryl Ketones
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A highly enantioselective cobalt-catalyzed hydroboration of diaryl ketones with pinacolborane was developed using chiral imidazole iminopyridine as a ligand to access chiral benzhydrols in good to excellent yields and ee. This protocol could be carried out in a gram scale under mild reaction conditions with good functional group tolerance. Chiral biologically active 3-substituted phthalide and (S)-neobenodine could be easily constructed through asymmetric hydroboration as a key step.
- Liu, Wenbo,Guo, Jun,Xing, Shipei,Lu, Zhan
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supporting information
p. 2532 - 2536
(2020/04/02)
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- Chiral Lithium Amido Aryl Zincates: Simple and Efficient Chemo- and Enantio-Selective Aryl Transfer Reagents
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An enantioselective aryl transfer is promoted using chiral tricoordinated lithium amido aryl zincates that are easily accessible reagents and whose chiral appendage is simply recovered for reuse. The arylation reaction is run in good yields (60 % average on twenty substrates) and high enantiomeric excesses (95 % ee average). This occurs whatever the ortho, meta, or para substituent borne by the substrate and a complete chemoselectivity is observed with respect to the aldehyde function. Sensitive groups such as nitriles, esters, ketones, and enolisable substrates resist to the action of the ate reagent, warranting a large scope to this methodology.
- Chaumont-Olive, Pauline,Rouen, Mathieu,Barozzino-Consiglio, Gabriella,Ben Abdeladhim, Amel,Maddaluno, Jacques,Harrison-Marchand, Anne
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supporting information
p. 3193 - 3197
(2019/01/25)
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- Substituent Position-Controlled Stereoselectivity in Enzymatic Reduction of Diaryl- and Aryl(heteroaryl)methanones
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We report here the discovery of a novel ketoreductase (KRED), named KmCR2, with a broad substrate spectrum on bioreduction of sterically bulky diaryl- and aryl(heteroaryl)methanones. The position of the substituent on aromatic rings (meta versus para or ortho) was revealed to control the stereospecificity of KmCR2. The stereoselective preparation of both enantiomers of diaryl- or aryl(heteroaryl)methanols using strategically engineered substrates with a traceless directing group (bromo group) showcased the potential application of this substrate-controlled bioreduction reaction. The combined use of substrate engineering and protein engineering, was demonstrated to be a useful strategy in efficiently improving stereoselectivity or switching stereopreference of enzymatic processes. (Figure presented.).
- Li, Zhining,Wang, Zexu,Wang, Yuhan,Wu, Xiaofan,Lu, Hong,Huang, Zedu,Chen, Fener
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supporting information
p. 1859 - 1865
(2019/03/07)
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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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- Development of Ferrocene-Based Diamine-Phosphine-Sulfonamide Ligands for Iridium-Catalyzed Asymmetric Hydrogenation of Ketones
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A series of air-stable, easily accessible tridentate ferrocene-based diamine-phosphine sulfonamide (f-diaphos) ligands were successfully developed for iridium-catalyzed asymmetric hydrogenation of ketones. The f-diaphos ligands exhibited excellent enantioselectivity and superb reactivity in Ir-catalyzed asymmetric hydrogenation of ketones (for arylalkyl ketones, (S)-selectivity, up to 99.4% ee, and 100 000 TON; for diaryl ketones, (R)-selectivity, up to 98.2% ee, and 10 000 TON). This protocol could be easily conducted on gram scale, thereby providing a chance to various drugs.
- Ling, Fei,Nian, Sanfei,Chen, Jiachen,Luo, Wenjun,Wang, Ze,Lv, Yaping,Zhong, Weihui
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p. 10749 - 10761
(2018/09/06)
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- Synthesis of new benzimidazolium salts and their application in the asymmetric arylation of aldehydes
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A series of novel chiral benzimidazolium salts, the precursor of N-heterocyclic carbene ligands, were designed and synthesized from 1,2-dibromobenzene. In situ prepared corresponding carbenes were tested in asymmetric Rh-catalyzed arylation of aromatic aldehydes, affording chiral diarylmethanols with high yields and moderate enantioselectivities.
- He, Wei-Ping,Zhou, Bi-Hui,Zhou, Ya-Li,Li, Xiang-Rong,Fan, Li-Mei,Shou, Hao-Wen,Li, Jie
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supporting information
p. 3152 - 3155
(2016/07/06)
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- Chiral-at-metal iridium complex for efficient enantioselective transfer hydrogenation of ketones
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A bis-cyclometalated iridium(iii) complex with metal-centered chirality catalyzes the enantioselective transfer hydrogenation of ketones with high enantioselectivities at low catalyst loadings down to 0.002 mol%. Importantly, the rate of catalysis and enantioselectivity are markedly improved in the presence of a pyrazole co-ligand. The reaction is proposed to proceed via an iridium-hydride intermediate exploiting metal-ligand cooperativity (bifunctional catalysis).
- Tian, Cheng,Gong, Lei,Meggers, Eric
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supporting information
p. 4207 - 4210
(2016/03/19)
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- Enantioselective addition of ArTi(OiPr)3 to aldehydes catalyzed by a titanium complex of an N-sulfonylated amino alcohol
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Asymmetric additions of ArTi(OiPr)3 to aldehydes catalyzed by a titanium catalyst of N-sulfonylated amino alcohols were reported, and results showed that the chiral N-sulfonylated amino alcohol with two stereogenic centers could catalyze the asymmetric addition of ArTi(OiPr)3 to aldehydes to afford desired secondary alcohols in good yields with good to excellent enantioselectivities of up to 95% ee.
- Chang, Shih-Ju,Zhou, Shuangliu,Gau, Han-Mou
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p. 9368 - 9373
(2015/02/19)
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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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- Preparation and catalytic performances of a molecularly imprinted RU-complex catalyst with an NH2 binding site on a SiO2 surface
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A catalyst surface with an active metal site, a shape-selective reaction space, and an NH2 binding site for o-fluorobenzophenone was designed and prepared by the molecular imprinting of a supported metal complex on a SiO2 surface. A ligand of a SiO2-supported Ru complex that has a similar shape to the product of o-fluorobenzophenone hydrogenation was used as a template. An NH2 binding site for o-fluorobenzophenone was spatially arranged on the wall of a molecularly imprinted cavity with a similar shape to the template. The structures of the SiO2-supported and molecularly imprinted Ru catalysts were characterized in a step-by-step manner by means of solid-state magic angle spinning (MAS) NMR, XPS, UV/Vis, N 2 adsorption, XRF, and Ru K-edge EXAFS. The molecularly imprinted Ru catalyst exhibited excellent shape selectivity for the transfer hydrogenation of benzophenone derivatives. It was found that the NH2 binding site on the wall of the molecularly imprinted cavity enhanced the adsorption of o-fluorobenzophenone, of which the reduction product was imprinted, whereas there was no positive effect in the case of o-methylbenzophenone, which cannot interact with the NH2 binding site through hydrogen bonding. Tailoring a pocket: A molecularly imprinted Ru-complex catalyst with an NH 2 binding site for o-fluorobenzophenone has been successfully designed and prepared on a SiO2 surface for shape-selective transfer hydrogenation (see scheme). Copyright
- Yang, Yong,Weng, Zhihuan,Muratsugu, Satoshi,Ishiguro, Nozomu,Ohkoshi, Shin-Ichi,Tada, Mizuki
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experimental part
p. 1142 - 1153
(2012/03/26)
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- CuII-catalyzed asymmetric hydrosilylation of diaryl- and aryl heteroaryl ketones: Application in the enantioselective synthesis of orphenadrine and neobenodine
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With certain amounts of sodium tert-butoxide and tert-butanol as additives, catalytic amounts of an inexpensive and easy-to-handle copper source Cu(OAc)2·H2O, a commercially available and air-stable non-racemic dipyridylphosphine ligand, as well as the stoichiometric desirable hydride donor polymethylhydrosiloxane (PMHS), formed a versatile in situ catalyst system for the enantioselective reduction of a broad spectrum of prochiral diaryl and aryl heteroarylketones in air, in high yields and with good to excellent enantioselectivities (up to 96 %). In particular, the practical viability of this process was evinced by its successful applications in the asymmetric synthesis of optically enriched potent antihistaminic drugs orphenadrine and neobenodine. Copyright
- Sui, Yao-Zong,Zhang, Xi-Chang,Wu, Jun-Wen,Li, Shijun,Zhou, Ji-Ning,Li, Min,Fang, Wenjun,Chan, Albert S. C.,Wu, Jing
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supporting information; experimental part
p. 7486 - 7492
(2012/07/27)
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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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- MPV reduction using AlIII-calix[4]arene Lewis acid catalysts: Molecular-level insight into effect of ketone binding
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Catalytic Meerwein-Ponndorf-Verley (MPV) reduction using Al III-calix[4]arene complexes is investigated as a model system that requires the bringing together of two different chemical species, ketone and alkoxide, within a six-membered transition state. Two-point versus one-point ketone binding is demonstrated to be the most salient feature that controls MPV catalysis rate. A 7.7-fold increase in rate is observed when comparing reactants consisting of a bidentate Cl-containing ketone and sterically and electronically similar but looser-binding ketones, which are substituted with H and F. The one-point and two-point nature of ketone binding for the various ketones investigated is independently assessed using a combination of structural data derived from single-crystal X-ray diffraction and DFT-based molecular modeling. Using MPV catalysis with inherently chiral calix[4]arenes, the effect of multiple point reactant binding on enantioselectivity is elucidated. A higher denticity of ketone binding appears to increase the sensitivity of the interplay between chiral active site structure and MPV reduction enantioselectivity.
- Nandi, Partha,Matvieiev, Yuriy I.,Boyko, Vyacheslav I.,Durkin, Kathleen A.,Kalchenko, Vitaly I.,Katz, Alexander
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experimental part
p. 42 - 49
(2011/12/13)
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- Structural influence of chiral tertiary aminonaphthol ligands on the asymmetric phenyl transfer to aromatic aldehydes
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A series of chiral tertiary aminonaphthol ligands were prepared from 2-naphthol, (S)-1-phenylethylamine, and aldehydes with diverse substituted groups. The results of asymmetric phenyl transfer to aromatic aldehydes catalyzed by these chiral ligands indicated that enantioselectivities were greatly influenced by the electronic and steric effects of the ligands. Copyright
- Wei, Hui,Yin, Lu,Luo, Haibin,Li, Xingshu,Chan, Albert S. C.
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experimental part
p. 222 - 227
(2012/03/27)
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- Continuous flow enantioselective arylation of aldehydes with ArZnEt using triarylboroxins as the ultimate source of aryl groups
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A continuous flow system for the synthesis of enantioenriched diarylmethanols from aldehydes is described. The system uses an amino alcohol-functionalized polystyrene resin as the catalyst, and the arylating agent is conveniently prepared by transmetallation of triarylboroxins with diethylzinc.
- Rolland, Julien,Cambeiro, Xacobe C.,Rodriguez-Escrich, Carles,Pericas, Miquel A.
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experimental part
(2010/04/22)
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- Practical implications of boron-to-zinc transmetalation for the catalytic asymmetric arylation of aldehydes
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(Chemical Equation Presented) Faster than believed: Transmetalation from aryl boronic acids and triaryl boroxines to diethylzinc takes place within minutes following a two-step, low-energy pathway (see picture), according to density functional calculations and reaction microcalorimetry measurements. The experimental conditions for a practical, atom-economical, and highly enantioselective catalytic arylation of a variety of aldehydes have been developed from these data.
- Jimeno, Ciril,Sayalero, Sonia,Fjermestad, Torstein,Colet, Gisela,Maseras, Feliu,Pericas, Miquel A.
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p. 1098 - 1101
(2008/09/20)
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- Method for Asymmetric Hydrosilylation of Ketones
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Method of asymmetrically hydrosilylating substrates using catalysts having a ligand of the compound of the formula (I) wherein R is optionally substituted alkyl, cycloalkyl, aryl or heteroaryl;R′ is hydrogen, optionally substituted lower alkyl; andR″ is hydrogen, halogen, optionally substituted alkyl, hydroxy, amino (e.g., primary, secondary or tertiary), alkenyl; or an enantiomer thereof; or an enantiomeric mixture thereof with a transition metal. Particularly suitable reactions include the asymmetric hydrosilylation of ketones.
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Page/Page column 6
(2008/12/04)
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- Chloroform is not solvent but activator for cobalt complex catalyst of enantioselective borohydride reduction
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For the enantioselective borohydride reduction of carbonyl compounds catalyzed by the optically active ketoiminatocobalt complexes, chloroform has been employed as a unique solvent for achieving a high enantioselectivity, whereas it was found that a catal
- Kokura, Ai,Tanaka, Saiko,Teraoka, Haruna,Shibahrara, Atsushi,Ikeno, Taketo,Nagata, Takushi,Yamada, Tohru
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- Polystyrene-supported amino alcohol ligands for the heterogeneous asymmetric addition of phenyl zinc reagents to aldehydes
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A family of polystyrene-supported amino alcohols, characterized by a high catalytic activity in alkyl transfer from zinc to formyl groups has been successfully tested in the enantioselective addition of phenyl zinc reagents to aldehydes to afford chiral diarylmethanols. Enantioselectivities higher than 90% (mean ee 90.5%; eight examples) are recorded with aromatic aldehydes in what represents the first successful use of heterogeneous, polymeric reagents for enantiocontrol in the phenylation of aldehydes.
- Castellnou, David,Fontes, Montserrat,Jimeno, Ciril,Font, Daniel,Solà, Lluís,Verdaguer, Xavier,Pericàs, Miquel A.
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p. 12111 - 12120
(2007/10/03)
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- CHIRAL TERTIARY AMINOALKYLNAPHTHOLS
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The invention relates to the compounds of formula: (I) which are as defined in the specification. Their use as chiral ligands in catalytic aryl transfer reactions to aromatic aldehydes is also described.
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Page/Page column 13; 16-17
(2008/06/13)
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- Highly enantioselective phenyl transfer to aryl aldehydes catalyzed by easily accessible chiral tertiary aminonaphthol
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(Chemical Equation Presented) A new chiral tertiary aminonaphthol ligand 3b served as a highly efficient ligand for the asymmetric catalytic phenyl transfer to aromatic aldehydes and a variety of chiral diarylmethanols was prepared in high ee values (ee up to 99%) and chemical yields. The straightforward syntheses of both 3b and its enantiomer provide an excellent opportunity for large-scale applications.
- Ji, Jian-Xin,Wu, Jing,Au-Yeung, Terry T.-L.,Yip, Chiu-Wing,Haynes, Richard K.,Chan, Albert S. C.
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p. 1093 - 1095
(2007/10/03)
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- 2-Piperidino-1,1,2-triphenylethanol: A Highly Effective Catalyst for the Enantioselective Arylation of Aldehydes
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Here we report the use of 2-piperidino-1,2,2-triphenylethanol (5) as an outstanding catalyst for the ligand-catalyzed arylation of aldehydes. The use of 5 and a 2/1 mixture of Et2Zn/Ph2Zn provided the corresponding chiral diarylcarbinols with enantiomeric excess of up to 99% ee. The effect of temperature on the reaction enantioselectivity was studied and the inversion temperature (Tinv) was determined to be 10 °C for reaction with p-tolylaldehyde. Most remarkably, lowering the amount of catalyst (5) to 0.5 mol % still afforded excellent levels of enantiocontrol (93.7% ee). Kinetics of the catalyzed and uncatalyzed arylation of aldehydes was studied by means of in situ FT-IR. The background uncatalyzed addition rates to p-tolylaldehyde when using pure Ph2Zn and Et2Zn/Ph 2-Zn (2/1) suggest that in the latter case a mixed zinc species forms (EtPhZn) minimizing the undesired nonselective addition. Formation of EtPhZn was modeled at the DFT calculation level. A four-center TS (TS-V) corresponding to the Et/Ph scrambling was localized along with two dimers (D-IV and D-VI). The model supports the hypothesis that Et/Ph exchange is a kinetically facile process. Gas evolution experiments during the formation of the active catalyst showed that the formation of an active site with a ONZn-Et (10) moiety is kinetically favored over ONZn-Ph (11). Finally, the phenyl transfer to benzaldehyde was modeled at the PM3(tm) level through anti and syn 5/4/4 tricyclic TS structures for both 10 and 11. The model could correctly predict the sense and selectivity of the overall process and predicted that 11 should be more selective than 10.
- Fontes, Montserrat,Verdaguer, Xavier,Sola, Lluis,Pericas, Miquel A.,Riera, Antoni
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p. 2532 - 2543
(2007/10/03)
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- Chiral [RuCl2(dipyridylphosphane)(1,2-diamine)] catalysts: Applications in asymmetric hydrogenation of a wide range of simple ketones
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The dipyridylphosphane/diamine - Ru complex combined with tBuOK in 2-propanol acts as a very effective catalyst system for the enantioselective hydrogenation of a diverse range of simple ketones including heteroaromatic ketones, substituted benzophenones, alkenyl ketones, and cyclopropyl ketones. The combination of desirable features, such as quantitative chemical yields within hours, broad substrate scope, excellent enantioselectivities (up to 99%), and high substrate-to-catalyst ratios, among others, makes the present catalyst system of high practical interest.
- Wu, Jing,Ji, Jian-Xin,Guo, Rongwei,Yeung, Chi-Hung,Chan, Albert S. C.
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p. 2963 - 2968
(2007/10/03)
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- Selective hydrogenation of benzophenones to benzhydrols. Asymmetric synthesis of unsymmetrical diarylmethanols
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(Graph presented) trans-RuCl2[P(C6H4-4-CH3) 3]2(NH2CH2CH2NH 2) acts as a highly effective precatalyst for the hydrogenation of a variety of benzophenone derivatives to benzhydrols that proceeds smoothly at 8 atm and 23-35 °C in 2-propanol containing t-C4H9OK with a substrate/catalyst ratio of 2000-20000. Use of a BINAP/chiral diamine Ru complex effects asymmetric hydrogenation of various ortho-substituted benzophenones and benzoylferrocene to chiral diarylmethanols with consistently high ee.
- Ohkuma, Takeshi,Koizumi, Masatoshi,Ikehira, Hideyuki,Yokozawa, Tohru,Noyori, Ryoji
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p. 659 - 661
(2007/10/03)
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- Preparative syntheses of optically pure ortho-substituted benzhydrols by asymmetric reductions of the corresponding benzophenones
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Lithium aluminium hydride previously treated with 2.5 equivalents of (S)-(+) or (R)-(-)-2-(2-iso-indolinyl)butan-1-ol 3 (readily available reagents) reduced the five ortho-substituted benzophenones 4-6, 8 and 10 into the corresponding optically active benzhydrols with nearly 100% enantiomeric excesses. Other examples of asymmetric reductions of prochiral benzophenones are given.
- Brown,Leze,Touet
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p. 841 - 844
(2007/10/02)
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