- Monophosphite ligands derived from carbohydrates and H8-BINOL: Highly enantioselective Rh-catalyzed asymmetric hydrogenations
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A series of monophosphite ligands derived from carbohydrates and H 8-BINOL have been synthesized. Excellent enantioselectivities (over 99% ee) were obtained when these ligands were applied in the Rh-catalyzed asymmetric hydrogenation of dimethy
- Huang, Hanmin,Liu, Xiongcai,Chen, Huilin,Zheng, Zhuo
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Read Online
- Enantioselective hydrogenation of enamides catalyzed by chiral rhodium-monodentate phosphite complexes
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Chiral monophosphites derived from BINOL are cheap and efficient ligands in the Rh-catalyzed hydrogenation of N-acyl enamides, providing amines with high degrees of enantioselectivity (up to 97.0% ee).
- Reetz, Manfred T.,Mehler, Gerlinde,Meiswinkel, Andreas,Sell, Thorsten
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Read Online
- Asymmetric enamide hydrogenation using planar-chiral cyrhetrenes
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The catalytic asymmetric hydrogenation of α-arylenamides using catalysts prepared in situ from [Rh(cod)2]BF4 and cyrhetrenyldiphosphines was effective with a range of enamides. The corresponding acetamides were obtained with up to 93
- Stemmler, René T.,Bolm, Carsten
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Read Online
- Catechol-based phosphoramidites: A new class of chiral ligands for rhodium-catalyzed asymmetric hydrogenations
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The synthesis and application of a new class of catechol-based phosphoramidites is described. Ees up to 99% were obtained in the rhodium-catalyzed asymmetric hydrogenation of dehydroamino acids and enamides.
- Hoen, Rob,Van Den Berg, Michel,Bernsmann, Heiko,Minnaard, Adriaan J.,De Vries, Johannes G.,Feringa, Ben L.
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Read Online
- Biocatalytic, Intermolecular C?H Bond Functionalization for the Synthesis of Enantioenriched Amides
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Directed evolution of heme proteins has opened access to new-to-nature enzymatic activity that can be harnessed to tackle synthetic challenges. Among these, reactions resulting from active site iron-nitrenoid intermediates present a powerful strategy to forge C?N bonds with high site- and stereoselectivity. Here we report a biocatalytic, intermolecular benzylic C?H amidation reaction operating at mild and scalable conditions. With hydroxamate esters as nitrene precursors, feedstock aromatic compounds can be converted to chiral amides with excellent enantioselectivity (up to >99 % ee) and high yields (up to 87 %). Kinetic and computational analysis of the enzymatic reaction reveals rate-determining nitrenoid formation followed by stepwise hydrogen atom transfer-mediated C?H functionalization.
- Arnold, Frances H.,Athavale, Soumitra V.,Gao, Shilong,Hirschi, Jennifer S.,Liu, Zhen,Mallojjala, Sharath Chandra
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supporting information
p. 24864 - 24869
(2021/10/15)
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- New chiral ferrocene/indole-based diphosphine ligands for Rh-catalyzed asymmetric hydrogenation of functionalized olefins
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Convenient synthesis of a new family of chiral ferrocene/indole-based diphosphine ligands, (Rc,Rp)-IndoFerroPhos (L), from (Sc,Rp)-PPFA and 2-(diphenylphosphino)indole has been described. These new ligands exhibited high efficiency in the Rh-catalyzed asymmetric hydrogenation of functionalized olefins including α-dehydroamino acid esters, α-enamides and dimethyl itaconate, in which up to >99% yield and 98% ee were achieved.
- Abbas, Zaheer,Ali, Aijaz,Hu, Xiang-Ping,Hu, Xin-Hu,Xu, You-Wei
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supporting information
(2020/04/02)
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- Diaza-Crown Ether-Bridged Chiral Diphosphoramidite Ligands: Synthesis and Applications in Asymmetric Catalysis
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A small library of diaza-crown ether-bridged chiral diphosphoramidite ligands was prepared. In the rhodium-catalyzed asymmetric hydrogenation and hydroformylation reactions, these ligands exhibited distinct properties in catalytic activity and/or enantioselectivity. Hydrogenated products with opposite absolute configurations could be obtained in high yields with excellent ee values by utilizing (S,S)-L1 and (S,S)-L3, respectively. Meanwhile, the addition of alkali metal cations caused variations in catalytic outcomes, showing the supramolecular tunability of these Rh/diphosphoramidite catalytic systems.
- Luo, Yier,Ouyang, Guanghui,Tang, Yuping,He, Yan-Mei,Fan, Qing-Hua
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p. 8176 - 8184
(2020/07/15)
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- Development of robust heterogeneous chiral rhodium catalysts utilizing acid?base and electrostatic interactions for efficient continuous-flow asymmetric hydrogenations
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Heterogeneous chiral Rh catalysts based on acid?base and electrostatic interactions have been developed. The robust catalysts demonstrate high activity and selectivity in the continuous-flow asymmetric hydrogenation of a wide variety of enamides and dehyd
- Saito, Yuki,Kobayashi, Shu
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supporting information
p. 16546 - 16551
(2020/11/09)
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- The enzymatic resolution of 1-(4-chlorophenyl)ethylamine by Novozym 435 to prepare a novel triazolopyrimidine herbicide
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The kinetic resolution of (R,S)-1-(4-chlorophenyl)ethylamine was accomplished using a commercial lipase from Candida antarctica (Novozym 435). The performance of this lipase was investigated for the enantioselective amidation of (R,S)-1-(4-chlorophenyl)ethylamine, leaving the target product (S)-1-(4-chlorophenyl)ethylamine in its unreacted form. The effects of various types of solvents and an acyl donor, the molar ratio of the substrate to the acyl donor, and the reaction temperature were studied. The optimum reaction conditions were found to result in amidation with methyl 2-tetrahydrofuroate at 40°C in methyl tert-butyl ether, with a substrate/acyl donor molar ratio of 1:2.4. The conversion rate of (R,S)-1-(4-chlorophenyl)ethylamine was 52%, with an enantiomeric excess of 99% towards the unreacted substrate in a reaction time of 22?hours. Finally, using optically pure (S)-1-(4-chlorophenyl)ethylamine as the raw material, the chemical synthesis of (S)-N-(1-(4-chlorphenyl)ethyl)-2-(5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidin-2-ylthio)acetamide, a novel triazolopyrimidine herbicide, was achieved, and the total yield and purity were 83.5% and 95.3%, respectively.
- Zhang, Yinjun,Cheng, Feifei,Yan, Hongde,Zheng, Jianyong,Wang, Zhao
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p. 1225 - 1232
(2018/09/25)
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- Optimization of 2-alkoxyacetates as acylating agent for enzymatic kinetic resolution of chiral amines
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In this study, the activity of acetic acid esters modified with electron withdrawing 2-alkoxy-groups was investigated as acylating agent in kinetic resolution (KR) of racemic amines. A homologous series of the isopropyl esters of four 2-alkoxyacetic acids (2-methoxy-, 2-ethoxy-, 2-propoxy- and 2-butoxyacetic acids) were prepared and investigated for enantiomer selective N-acylation, catalyzed by lipase B from Candida antarctica, under batch and continuous-flow conditions. In the first set of experiments, isopropyl 2-propoxyacetate showed the highest effectivity with all of the four racemic amines [(±)-1-phenylethylamine, (±)-4-phenylbutan-2-amine, (±)-heptan-2-amine and (±)-1-methoxypropane-2-amine] in the set enabling excellent conversions (≥46%) and enantiomeric excess values (ee ≥ 99%) with each amines in continuous-flow mode KRs under the optimized reaction conditions. In a second set of experiments, KRs of five additional amines – being substituted derivatives of (±)-1-phenylethylamine – further demonstrated the usefulness of isopropyl 2-propoxyacetate – being the best acylating agent in the first set of KRs – in KRs leading to (R)-N-propoxyacetamides with high ee values (≥99.8%).
- Oláh, Márk,Kovács, Dániel,Katona, Gabriel,Hornyánszky, Gábor,Poppe, László
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p. 3663 - 3670
(2018/06/04)
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- Manganese-Catalyzed Direct Conversion of Ester to Amide with Liberation of H2
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A simple and efficient Mn-catalyzed acylation of amines is achieved using both acyl and alkoxy functions of unactivated esters with the liberation of molecular hydrogen as a sole byproduct. The present protocol provides an atom-economical and sustainable route for the synthesis of amides from esters by employing an earth-abundant manganese salt and inexpensive phosphine-free tridentate ligand.
- Mondal, Akash,Subaramanian, Murugan,Nandakumar, Avanashiappan,Balaraman, Ekambaram
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supporting information
p. 3381 - 3384
(2018/06/11)
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- Asymmetric Synthesis of Chiral Primary Amines by Ruthenium-Catalyzed Direct Reductive Amination of Alkyl Aryl Ketones with Ammonium Salts and Molecular H2
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A ruthenium/C3-TunePhos catalytic system has been identified for highly efficient direct reductive amination of simple ketones. The strategy makes use of ammonium acetate as the amine source and H2 as the reductant and is a user-friendly and operatively simple access to industrially relevant primary amines. Excellent enantiocontrol (>90% ee for most cases) was achieved with a wide range of alkyl aryl ketones. The practicability of this methodology has been highlighted by scalable synthesis of key intermediates of three drug molecules. Moreover, an improved synthetic route to the optimal diphosphine ligand C3-TunePhos is also presented.
- Tan, Xuefeng,Gao, Shuang,Zeng, Weijun,Xin, Shan,Yin, Qin,Zhang, Xumu
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supporting information
p. 2024 - 2027
(2018/02/19)
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- Amine dehydrogenases: Efficient biocatalysts for the reductive amination of carbonyl compounds
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Amines constitute the major targets for the production of a plethora of chemical compounds that have applications in the pharmaceutical, agrochemical and bulk chemical industries. However, the asymmetric synthesis of α-chiral amines with elevated catalytic efficiency and atom economy is still a very challenging synthetic problem. Here, we investigated the biocatalytic reductive amination of carbonyl compounds employing a rising class of enzymes for amine synthesis: amine dehydrogenases (AmDHs). The three AmDHs from this study-operating in tandem with a formate dehydrogenase from Candida boidinii (Cb-FDH) for the recycling of the nicotinamide coenzyme-performed the efficient amination of a range of diverse aromatic and aliphatic ketones and aldehydes with up to quantitative conversion and elevated turnover numbers (TONs). Moreover, the reductive amination of prochiral ketones proceeded with perfect stereoselectivity, always affording the (R)-configured amines with more than 99% enantiomeric excess. The most suitable amine dehydrogenase, the optimised catalyst loading and the required reaction time were determined for each substrate. The biocatalytic reductive amination with this dual-enzyme system (AmDH-Cb-FDH) possesses elevated atom efficiency as it utilizes the ammonium formate buffer as the source of both nitrogen and reducing equivalents. Inorganic carbonate is the sole by-product.
- Knaus, Tanja,B?hmer, Wesley,Mutti, Francesco G.
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p. 453 - 463
(2017/08/14)
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- Asymmetric Allylic Alkylation and Hydrogenation with Transition Metal Complexes of Diphosphite Ligands Based on (1S,2S)-Trans-1,2-cyclohexanediol
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Abstract: The preparation of new palladium complexes in situ that were composed of a series of chiral diphosphite ligands, which were derived from (1S,2S)-trans-1,2-cyclohexanediol, have been described. It was found that (1S,2S)-bis[(S)-1,1′-binaphthyl-2,
- Pang, Zengbo,Tian, Mi,Li, Haifeng,Wang, Lailai
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p. 893 - 899
(2017/03/24)
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- An unexpected copper-catalyzed carbonylative acetylation of amines
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A novel copper-catalyzed carbonylative acetylation of amines has been developed. With peroxide as the oxidant as well as the methyl source with a copper catalyst under CO pressure, good yields of N-acetyl amides could be obtained. Notably, this is the first example of carbonylative acetylation.
- Li, Yahui,Wang, Changsheng,Zhu, Fengxiang,Wang, Zechao,Fran?ois Soulé, Jean,Dixneuf, Pierre H.,Wu, Xiao-Feng
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supporting information
p. 142 - 144
(2016/12/27)
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- A Single Lipase-Catalysed One-Pot Protocol Combining Aminolysis Resolution and Aza-Michael Addition: An Easy and Efficient Way to Synthesise β-Amino Acid Esters
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A novel one-pot protocol combining aza-Michael addition and aminolysis resolution was developed to obtain chiral β-amino acid esters with lipase B from Candida antarctica (CAL-B) as the only catalyst. This method is conducted under mild reaction conditions and is very easy to handle. After a series of detailed optimization studies, ten racemic aromatic or aliphatic amines were subjected to this one-pot procedure, and twelve chiral β-amino acid esters and ten chiral amides were successfully synthesised with excellent ee values in theoretical yields. Scaled-up procedures also worked without apparent reduction in reaction rate or enantioselectivity, which makes this method suitable for large-scale production of chiral β-amino acid esters. A one-pot protocol for simultaneous synthesis of chiral β-amino acid esters and amides was developed by combining single lipase B from Candida antarctica (CAL-B) catalysed aza-Michael addition and aminolysis resolution. This method requires mild reaction conditions and is very easy to handle. Chiral β-amino acid esters and chiral amides were obtained with excellent ee values and in theoretical yields.
- Xu, Fan,Wu, Qiongsi,Chen, Xiaoyang,Lin, Xianfu,Wu, Qi
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supporting information
p. 5393 - 5401
(2015/08/24)
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- Chiral diphosphites derived from (1R,2R)-trans-1,2-cyclohexanediol: A new class of ligands for asymmetric hydrogenations
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A series of novel chiral diphosphite ligands was easily prepared in a few steps from commercial (1R,2R)-trans-1,2-cyclohexanediol as the chiral source, and successfully employed in the Rh-catalyzed asymmetric hydrogenation of α,β-unsaturated carboxylic ac
- Pang, Zeng-Bo,Li, Hai-Feng,Tian, Mi,Wang, Lai-Lai
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p. 1389 - 1393
(2015/12/09)
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- Transaminases applied to the synthesis of high added-value enantiopure amines
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Critical parameters affecting the stereoselective amination of (hetero)aromatic ketones using transaminases have been studied, such as temperature, pH, substrate concentration, cosolvent, and source and percentage of amino donor, to further optimize the production of enantiopure amines using both (S)- and (R)-selective biocatalysts from commercial suppliers. Interesting enantiopure amino building blocks have been obtained, overcoming some limitations of traditional chemical synthetic methods. Representative processes were scaled up, affording halogenated and heteroaromatic amines in enantiomerically pure form and good isolated yields.
- Paul, Caroline E.,Rodriguez-Mata, Maria,Busto, Eduardo,Lavandera, Ivan,Gotor-Fernandez, Vicente,Gotor, Vicente,Garcia-Cerrada, Susana,Mendiola, Javier,De Frutos, Oscar,Collado, Ivan
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supporting information
p. 788 - 792
(2014/07/08)
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- Metallacrown ether catalysts containing phosphine-phosphite polyether ligands for Rh-catalyzed asymmetric hydrogenation - Enhancements in activity and enantioselectivity
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A new class of tunable metallacrown ether rhodium catalysts based on α,ω-(phosphine-phosphite) polyether ligands were prepared either by a template-induced method or by a nontemplate procedure. For the asymmetric hydrogenation of α-arylenamides with the a
- Song, Feng-Tao,Ouyang, Guang-Hui,Li, Yong,He, Yan-Mei,Fan, Qing-Hua
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supporting information
p. 6713 - 6719
(2016/02/18)
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- Enantioselective synthesis of (R)-2-arylpropanenitriles catalysed by ene-reductases in aqueous media and in biphasic ionic liquid-water systems
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The enantioselective reduction of α-methylene nitrile derivatives catalysed by ene-reductases affords the corresponding (R)-2-arylpropanenitriles with high conversion values. The reaction is investigated either in aqueous medium (with an organic cosolvent or by loading the substrate onto hydrophobic resins) or in a biphasic ionic liquid-water system. The use of ionic liquids, herein with isolated ene-reductases, is found to improve the work-up and the substrate recovery method. The synthetic manipulation of the final chiral nitrile derivatives indicates how this biocatalysed method can be exploited for the preparation of a wide range of chiral compounds.
- Brenna, Elisabetta,Crotti, Michele,Gatti, Francesco G.,Manfredi, Alessia,Monti, Daniela,Parmeggiani, Fabio,Santangelo, Sara,Zampieri, Davila
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p. 2425 - 2431
(2014/08/18)
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- Rhodium-catalyzed enantioselective hydrogenation of oxime acetates
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Rh-catalyzed enantioselective hydrogenation of oxime acetates was first reported, which afforded a new approach for chiral amine synthesis.
- Huang, Kexuan,Li, Shengkun,Chang, Mingxin,Zhang, Xumu
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supporting information
p. 484 - 487
(2013/03/29)
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- Practical enantioselective hydrogenation of α-aryl- and α-carboxyamidoethylenes by rhodium(I)-{1,2-bis[(o-tert-butoxyphenyl) (phenyl)phosphino]ethane}
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The rhodium(I)-{1,2-bis[(o-tert-butoxyphenyl)(phenyl)phosphino]ethane} [Rh(I)-(t-Bu-SMS-Phos)] catalyst system displayed prime efficiency in the hydrogenation of large series of aamidostyrenes and a-amidoacrylates. Up to >99.9% enantiomeric excesses coupl
- Mohar, Barbara,Stephan, Michel
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p. 594 - 600
(2013/05/09)
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- Asymmetric synthesis of nonracemic primary amines via spiroborate-catalyzed reduction of pure (E)- and (Z)-O-benzyloximes: Applications toward the synthesis of calcimimetic agents
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Highly enantiopure (1-aryl)- and (1-naphthyl)-1-ethylamines were synthesized by the borane-mediated reduction of single-isomeric (E)- and (Z)-O-benzyloxime ethers using the stable spiroborate ester derived from (S)-diphenyl valinol and ethylene glycol as the chiral catalyst. Primary (R)-arylethylamines were prepared by the reduction of pure (Z)-ethanone oxime ethers in up to 99% ee using 15% of catalyst. Two convenient and facile approaches to the synthesis of new and known calcimimetic analogues employing enantiopure (1-naphthalen-1-yl)ethylamine as chiral precursor are described.
- Ou, Wenhua,Espinosa, Sandraliz,Meléndez, Héctor J.,Farré, Silvia M.,Alvarez, Jaime L.,Torres, Valerie,Martínez, Ileanne,Santiago, Kiara M.,Ortiz-Marciales, Margarita
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p. 5314 - 5327
(2013/07/25)
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- Reaction pathway and rate-determining step of the Schmidt rearrangement/fragmentation: A kinetic study
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The Schmidt rearrangement of substituted 3-phenyl-2-butanone with trimethylsilyl azide in 90% (v/v) aqueous TFA gave two types of product, fragmentation and rearrangement, the ratio of which depends on the substituent: more fragmentation for a more electron-donating substituent. Rate measurements by azotometry indicated the presence of an induction period, and the pseudo-first-order rate constants showed saturation kinetics with respect to the azide concentration. It was indicated that the reaction proceeds through pre-equilibrium in the formation of iminodiazonium (ID) ion and that the N 2 liberation from the ID ion is rate-determining. Under high azide concentration conditions, where the effective reactant is the ID ion, the reaction gave a linear Hammett plot with a value of -0.50. The observed substituent effects on the rate and the product selectivity imply that path bifurcation on the way from the rate-determining TS to the product states occurs, as suggested by previous molecular dynamics simulations, in a similar manner to the analogous Beckmann rearrangement/fragmentation reactions.
- Akimoto, Ryo,Tokugawa, Takehiro,Yamamoto, Yutaro,Yamataka, Hiroshi
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experimental part
p. 4073 - 4078
(2012/06/29)
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- Ritter reaction in subcritical water: An efficient and green method for amides synthesis
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Ritter reaction was carried out efficiently in subcritical water with catalytic amount of trifluoromethanesulfonic acid. The amides were formed in good to excellent yields from secondary alcohols and tert-butanol with various nitriles.
- Jiang, Shengqian,Wang, Zhouyu,Jiang, Zhenju,Li, Jianhui,Zhou, Shulin,Pu, Long
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experimental part
p. 24 - 28
(2012/08/08)
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- Cyclohexylamine oxidase as a useful biocatalyst for the kinetic resolution and dereacemization of amines
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The biocatalytic performance of a cloned cyclohexylamine oxidase derived from Brevibacterium oxydans IH-35A towards structurally different amines was investigated. Cycloalkyl primary amines, alkyl aryl amines, and α-carbon-substituted aliphatic amines were identified as suitable substrates for the biocatalyst based on an activity assay. Kinetic resolutions of several amines by either recombinant whole cells or crude enzyme extracts prepared therefrom gave enantiomerically pure (R)-amines besides the corresponding ketones. When cyclohexylamine oxidase in combination with a borane-ammonia complex as reducing agent was applied to the deracemization of several substrates, excellent enantiomeric ratios (>99:1) and good isolated yields (62%-75%) of the corresponding (R)-amines were obtained.
- Leisch, Hannes,Grosse, Stephan,Iwaki, Hiroaki,Hasegawa, Yoshie,Lau, Peter C.K.
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- Readily available and recoverable chiral ionic phosphite ligands for the highly enantioselective hydrogenation of functionalized olefins
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A series of novel ionic phosphite ligands bearing carbohydrate groups were conveniently synthesized and successfully applied in the asymmetric hydrogenation of enamides, α-dehydroamino acid esters, and dimethyl itaconate. High efficiency and excellent reu
- Zhao, Yingwei,Huang, Hanmin,Shao, Jianping,Xia, Chungu
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experimental part
p. 769 - 774
(2011/08/06)
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- Dynamic path bifurcation in the Beckmann reaction: Support from kinetic analyses
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The reactions of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles when the migrating groups have reasonable stability as cations. The reactions of oxime sulfonates of 1-substituted-phenyl-2-propanone derivatives (7-X) and related substrates (8-X, 9a-X) in aqueous CH3CN gave both rearrangement products (amides) and fragmentation products (alcohols), the ratio of which depends on the system; the reactions of 7-X gave amides predominantly, whereas 9a-X yielded alcohols as the major product. The logk-logk plots between the systems gave excellent linear correlations with slopes of near unity. The results support the occurrence of path bifurcation after the rate-determining TS of the Beckmann rearrangement/fragmentation reaction, which has previously been proposed on the basis of molecular dynamics simulations. It was concluded that path-bifurcation phenomenon could be more common than thought and that a reactivity-selectivity argument based on the traditional TS theory may not always be applicable even to a well-known textbook organic reaction.
- Yamamoto, Yutaro,Hasegawa, Hiroto,Yamataka, Hiroshi
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experimental part
p. 4652 - 4660
(2011/07/29)
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- A fast and sensitive assay for measuring the activity and enantioselectivity of transaminases
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A fast and sensitive method for screening transaminase activity and enantioselectivity, using d- and l-amino acid oxidases, allows new amine substrates to be rapidly identified. The Royal Society of Chemistry 2011.
- Hopwood, Jennifer,Truppo, Matthew D.,Turner, Nicholas J.,Lloyd, Richard C.
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supporting information; experimental part
p. 773 - 775
(2011/04/15)
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- HBF4·OEt2 as a mild and versatile reagent for the Ritter amidation of olefins: A facile synthesis of secondary amides
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A variety of alkenes undergo smooth amidation with nitriles in the presence of HBF4·OEt2 at room temperature under mild conditions to afford the corresponding secondary amides in good to excellent yields. This is a highly efficient method for the preparation of α-aryl ethyl amides especially from vinyl arenes without any side reactions such as olefin polymerization. The use of readily available and easy to handle reagent HBF4·OEt2 makes this method simple, convenient, and practical.
- Subba Reddy,Sivasankar Reddy,Madan, Ch.,Yadav
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experimental part
p. 4827 - 4829
(2010/10/02)
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- Electron-donating and rigid p-stereogenic bisphospholane ligands for highly enantioselective rhodium-catalyzed asymmetric hydrogenations
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More electron donating, more rigid: A new highly electron-donating P-stereogenic bisphospholane ligand (ZhangPhos) was synthesized in a practical and highly enantioselective manner from a commercially available chiral source. Better or comparable enantioselectivities and reactivities than TangPhos were achieved in rhodium-catalyzed hydrogenation of various functionalized olefins (see scheme; nbd=3,5-norbornadiene). Copyright
- Zhang, Xiaowei,Huang, Kexuan,Hou, Guohua,Cao, Bonan,Zhang, Xumu
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supporting information; experimental part
p. 6421 - 6424
(2010/12/19)
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- Readily available chiral phosphine-aminophosphine ligands derived from 1-phenylethylamine for Rh-catalyzed enantioselective hydrogenations
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A series of new chiral phosphine-aminophosphine ligands have been prepared via a two- or three-step transformation from commercially available and inexpensive (S)-1-phenylethylamine, and successfully used in the rhodium-catalyzed asymmetric hydrogenation
- Zhou, Xiao-Mao,Huang, Jia-Di,Luo, Li-Bin,Zhang, Cheng-Lu,Zheng, Zhuo,Hu, Xiang-Ping
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experimental part
p. 420 - 424
(2010/07/02)
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- Supramolecular chiral dendritic monophosphites assembled by hydrogen bonding and their use in the Rh-catalyzed asymmetric hydrogenation
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A new type of supramolecular chiral dendritic monophosphite ligands has been prepared via a hydrogen-bonding assembly. The Rh complexes of these supramolecular ligands have been successfully applied in the asymmetric hydrogenation of enamides and dehydroa
- Li, Yong,He, Yan-Mei,Li, Zhi-Wei,Zhang, Feng,Fan, Qing-Hua
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experimental part
p. 1890 - 1895
(2009/06/28)
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- Heterogeneously catalyzed asymmetric hydrogenation of α-arylenamides over immobilized RhBPE and RhDUPHOS complexes
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Optically active α-1-arylalkylamine derivatives were successfully synthesized through heterogeneous asymmetric hydrogenation of α-arylenamides over immobilized RhBPE and RhDUPHOS complexes on aluminum-containing M41S and SBA-15 type materials. The heterog
- Crosman, Adrian,Hoelderich, Wolfgang F.
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experimental part
p. 229 - 237
(2009/10/16)
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- Enantioselective hydrogenation of N-H imines
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(Figure Presented) N-H ketoimines 3a-3v are readily prepared in high yield via organometallic addition to nitriles and isolated as corresponding bench-stable hydrochloride salts. Homogeneous asymmetric hydrogenation of unprotected N-H ketoimines 3a-3v usi
- Hou, Guohua,Gosselin, Francis,Li, Wei,McWilliams, J. Christopher,Sun, Yongkui,Weisel, Mark,O'Shea, Paul D.,Chen, Cheng-Yi,Davies, Ian W.,Zhang, Xumu
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supporting information; experimental part
p. 9882 - 9883
(2009/12/06)
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- o-Benzenedisulfonimide as a reusable Bronsted acid catalyst for Ritter-type reactions
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Reactions between various benzyl alcohols or tert-butyl alcohol and nitriles were carried out in the presence of catalytic amounts (usually 10-20 mol-%) of o-benzenedisulfonimide as a Bronsted acid catalyst; the reaction conditions were mild and the yields of amides were good. The catalyst was easily recovered and purified, ready to be used in further reactions, with economic and ecological advantages. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.
- Barbero, Margherita,Bazzi, Stefano,Cadamuro, Silvano,Dughera, Stefano
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experimental part
p. 430 - 436
(2009/07/19)
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- Highly enantioselective hydrogenation of enamides catalyzed by chiral phosphoric acids
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A highly enantioselective hydrogenation of enamides catalyzed by a dual chiral-achiral acid system was developed. By employing a substoichiometric amount of a chiral phosphoric acid and acetic acid, catalyst loadings as low as 1 mol % of the chiral cataly
- Li, Guilong,Antilla, Jon C.
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supporting information; experimental part
p. 1075 - 1078
(2009/07/25)
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- Click-connected ligand scaffolds: macrocyclic chelates for asymmetric hydrogenation
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Click chemistry is used to construct ligand scaffolds for a series of chiral diphosphites. Enantioselectivity as high as 97% ee is obtained using these click ligands in rhodium-catalyzed asymmetric hydrogenation. Control experiments and spectroscopic data suggest that a 16-membered P,P-macrocyclic Rh(1) chelate is formed.
- Qing, Zhang,Takacs, James M.
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p. 545 - 548
(2008/09/17)
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- Modular chiral dendritic monodentate phosphoramidite ligands for Rh(II)-catalyzed asymmetric hydrogenation: Unprecedented enhancement of enantioselectivity
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Modular chiral dendrimers with monodentate phosphoramidite ligands located at the core were synthesized and applied in the Rh-catalyzed asymmetric hydrogenations, afforded unprecedented enhancement of enantioselectivity. The Royal Society of Chemistry.
- Zhang, Feng,Li, Yong,Li, Zhi-Wei,He, Yan-Mei,Zhu, Shou-Fei,Fan, Qing-Hua,Zhou, Qi-Lin
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supporting information; experimental part
p. 6048 - 6050
(2009/05/06)
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- CATALYTIC ASYMMETRIC SYNTHESIS OF PRIMARY AMINES VIA BORANE REDUCTION OF OXIME ETHERS USING SPIROBORATE ESTERS
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Asymmetric reduction of arylalkyl and pyridylalkyl ketoxime ether with borane catalyzed by several chiral spiroborates derived from non-racemic 1,2-amino alcohols are presented. Complete conversion of oxime to primary amine is highly dependant of the catalyst, source and amount of borane and temperature. The conversion and enantioselectivity is determined by the benzylic substitution of the oxime. After optimization, a catalyst derived from diphenyl valinol could, successfully, afford primary amines with good yield and enantioselectivity up to 99% ee. Using the developed methodology, other related non-racemic primary pyridyl alkyl methanamines were also prepared in high chemical yield and excellent enantioselectivity.
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Page/Page column 12-13; 23-25
(2008/06/13)
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- Chiral 1,2,3,4-tetrahydro-1-naphthylamine-derived phosphine-phosphoramidite ligand (THNAPhos): Application in highly enantioselective hydrogenations of functionalized C=C bonds
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We have recently reported a new chiral 1,2,3,4-tetrahydro-1-naphthylamine- derived phosphine-phosphoramidite ligand, (Rc,Ra)- THNAPhos, that is highly efficient in the rhodium-catalyzed asymmetrichydrog enation of a broad range of aenol ester phosphonates. To further demonstrate the utility of THNAPhos in asymmetric hydrogenation, in this paper, we describe its new application in the asymmetrichy drogenation of α-dehydroamino acid esters, enamides, dimethyl itaconate and α-enamido phosphonates. The results disclosed that the Rh/(Rc,Ra)-THNAPhos complex is highly effective for the enantioselective hydrogenation of these kinds of functionalized C=C olefins, affording the corresponding hydrogenation product in excellent enantioselectivities (normally over 99% ee).
- Qiu, Min,Hu, Xiang-Ping,Wang, Dao-Yong,Deng, Jun,Huang, Jia-Di,Yu, Sai-Bo,Duan, Zheng-Chao,Zheng, Zhuo
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scheme or table
p. 1413 - 1418
(2009/06/18)
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- Modular phosphine-aminophosphine ligands based on chiral 1,2,3,4-tetrahydro-1-naphthylamine backbone: A new class of practical ligands for enantioselective hydrogenations
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A series of new chiral phosphine-aminophosphine ligands [(R)-HW-Phos] has been prepared from (R)-1,2,3,4-tetrahydro-1-naphthylamine through a two-step procedure, and successfully applied in the rhodium-catalyzed asymmetric hydrogenation of various functionalized olefins such as α-enol ester phosphonates, α-enamido phosphonates, (Z)-β-(acylamino)acrylates and so on. Excellent enantioselectivities have been achieved in the hydrogenation of most substrates tested, demonstrating the high potential of these newly developed phosphine-aminophosphine ligands in asymmetric catalysis. The present research also discloses that these newly developed phosphine-aminophosphine ligands are more efficient than that derived from (S)-1-phenylethylamine, suggesting that the increased rigidity conferred by a cyclohexyl fragment in these phosphine-aminophosphine ligands has a positive effect in the asymmetric induction.
- Qiu, Min,Hu, Xiang-Ping,Huang, Jia-Di,Wang, Dao-Yong,Deng, Jun,Yu, Sai-Bo,Duan, Zheng-Chao,Zheng, Zhuo
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experimental part
p. 2683 - 2689
(2009/10/14)
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- Axial 4,4′,6,6′-tetrakis-trifluoromethyl-biphenyl-2, 2′diamine (TF-BIPHAM): Resolution and applications in asymmetric hydrogenation
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(Equation Presented) The racemic TF-BIPHAM was resolved for the first time, and the effectiveness of the resolved diamine was demonstrated by highly enantioselective hydrogenation of α-aryl enamides and α-dehydroamino acid esters using readily accessible
- Wang, Chun-Jiang,Gao, Feng,Liang, Gang
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supporting information; experimental part
p. 4711 - 4714
(2009/05/31)
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- Novel chiral phosphine-phosphoramidite ligands derived from 1-naphthylamine for highly efficient Rh-catalyzed asymmetric hydrogenation
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A new chiral phosphine-phosphoramidite ligand (S)-HY-Phos 1 has been prepared from 1-naphthylamine via a two-step transformation, and successfully applied in the Rh-catalyzed asymmetric hydrogenation of various functionalized olefins, including α-(acetamido)cinnamates, enamides and α-enol ester phosphonates, in which up to 98% ee, 99% ee and 99% ee were achieved, respectively.
- Yu, Sai-Bo,Huang, Jia-Di,Wang, Dao-Yong,Hu, Xiang-Ping,Deng, Jun,Duan, Zheng-Chao,Zheng, Zhuo
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p. 1862 - 1866
(2008/12/21)
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- Asymmetric synthesis of primary amines via the spiroborate-catalyzed borane reduction of oxime ethers
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The enantioselective borane reduction of O-benzyloxime ethers to primary amines was studied under catalytic conditions using the spiroborate esters 5-10 derived from nonracemic 1,2-amino alcohols and ethylene glycol. Effective catalytic conditions were achieved using only 10% of catalyst 5 derived from diphenylvalinol in dioxane at 0°C resulting in complete conversion to the corresponding primary amine in up to 99% ee.
- Huang, Xiaogen,Ortiz-Marciales, Margarita,Huang, Kun,Stepanenko, Viatcheslav,Merced, Francisco G.,Ayala, Angel M.,Correa, Wildeliz,De Jesus, Melvin
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p. 1793 - 1795
(2008/02/02)
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- The ritter reaction under truly catalytic bronsted acid conditions
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Simple organic acids like 2,4-dinitrobenzenesulfonic acid (DNBSA) catalyze the Ritter reaction of secondary benzylic alcohols giving rise to the corresponding N-benzylacetamides in usually high yields. Reactions can be conducted without exclusion of oxygen and without the need of dry solvents. With tertiary α,α-dimethylbenzylic alcohols a different pathway involving a formal dimerization reaction takes place under the acid-catalytic conditions used. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Sanz, Roberto,Martinez, Alberto,Guilarte, Veronica,Alvarez-Gutierrez, Julia M.,Rodriguez, Felix
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p. 4642 - 4645
(2008/03/12)
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- Practical by ligand design: A new class of monodentate phosphoramidite ligands for rhodium-catalyzed enantioselective hydrogenations
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A new class of low-cost and easy-to-prepare monodentate phosphoramidite ligands (Cydam-Phos) has been developed from readily accessible and cheap trans-1,2-diaminocyclohexane as starting material through a three-step transformation. This type of ligands exhibited excellent enantioseletivities and high activities in rhodium(I)-catalyzed asymmetric hydrogenations of dehydro-α-amino acid methyl esters 9 (ee: 96.2-99.8%) and acetylenamides 11 (91.8-98.8%). The remarkable substituent effects exhibited by the ligands on the enantioselective control of the catalysis are rationalized on the basis of molecular structure of the catalyst precursor.
- Zhao, Baoguo,Wang, Zheng,Ding, Kuiling
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p. 1049 - 1057
(2007/10/03)
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- Allosteric effects in asymmetric hydrogenation catalysis? Asymmetric induction as a function of the substrate and the backbone flexibility of C 1-symmetric diphosphines in rhodium-catalysed hydrogenations
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The new unsymmetrical, optically active ligands 1,2-C2H 4(PPh2)(2′R,5′R-2′,5′- dimethylphospholanyl) (La) and 1,3-C3H 6(PPh2)(2′R,5′R-2′,5′- dimethylphospholanyl) (Lb) form complexes of the type [Rh(L)(cyclooctadiene)][BF4] where L = La (1a) or L b (1b), [PtCl2(L)] where L = La (2a) or L b (2b) and [PdCl2(L)] where L = La (3a) or Lb (3b). The crystal structures of 2a and 2b show the chelate ligand backbones adopt δ-twist and flattened chair conformations respectively. Asymmetric hydrogenation of enamides and dehydroaminoesters using 1a and 1b as catalysts show that the ethylene-backboned diphosphine La gives a more efficient catalyst in terms of asymmetric induction than the propylene-backboned analogue Lb. The greatest enantioselectivities were obtained with 1a and enamide substrates with ees up to 91%. Substrate-induced conformational changes in the Rh-diphosphine chelates are proposed to explain some of the ees observed in the hydrogenation of enamides. The Royal Society of Chemistry 2006.
- Baber, Angharad,De Vries, Johannes G.,Orpen, A. Guy,Pringle, Paul G.,Von Der Luehe, Karl
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p. 4821 - 4828
(2007/10/03)
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- Unsymmetrical ferrocenylethylamine-derived monophosphoramidites: Highly efficient chiral ligands for Rh-catalyzed enantioselective hydrogenation of enamides and α-dehydroamino acid derivatives
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A new family of unsymmetrical ferrocenylethylamine-derived monophosphoramidites were synthesized and successfully applied in the Rh-catalyzed enantioselective hydrogenation of a range of enamides and α-dehydroamino acid esters, and ee values of up to 99.5% were obtained for both types of substrate. These results suggest that unsymmetrical amine-derived monophosphoramidites can also exhibit excellent enantioselectivity for a broad range of substrates, comparable to or higher than those of the most efficient symmetrical amine-derived monophosphoramidites reported thus far.
- Zeng, Qing-Heng,Hu, Xiang-Ping,Duan, Zheng-Chao,Liang, Xin-Miao,Zheng, Zhuo
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p. 393 - 396
(2007/10/03)
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- Readily available phosphine-phosphoramidite ligands for highly efficient Rh-catalyzed enantioselective hydrogenations
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(Chemical Equation Presented) A new family of air- and moisture-stable phosphine-phosphoramidite ligands (PEAPhos) has been prepared from commercially available and inexpensive (S)-α-phenylethylamine through a two- or three-step transformation and success
- Huang, Jia-Di,Hu, Xiang-Ping,Duan, Zheng-Chao,Zeng, Qing-Hen,Yu, Sai-Bo,Deng, Jun,Wang, Dao-Yong,Zheng, Zhuo
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p. 4367 - 4370
(2007/10/03)
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- Readily available, recoverable and soluble polymer-monophosphite ligands for highly enantioselective Rh-catalyzed hydrogenation
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A new family of readily available, recoverable and soluble polymer-monophosphite ligands were prepared and successfully used in the Rh-catalyzed asymmetric hydrogenation of enamides and β-dehydroamino acid esters, in which up to 99 and 99.9% ee were obtai
- Hu, Xiang-Ping,Huang, Jia-Di,Zeng, Qing-Heng,Zheng, Zhuo
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p. 293 - 295
(2008/02/08)
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- New unsymmetrical hybrid ferrocenylphosphine-phosphoramidite ligands derived from H8-BINOL for highly efficient Rh-catalyzed enantioselective hydrogenation
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A series of new H8-BINOL-derived unsymmetrical hybrid ferrocenylphosphine-phosphoramidite ligands have been synthesized and successfully used in Rh-catalyzed asymmetric hydrogenations. The same or higher enantioselectivities (99.9% ee) were achieved in the hydrogenation of dimethyl itaconate and α-dehydroamino acid esters as those obtained with BINOL-derived analogues. However, slightly lower enantioselectivities (99.0% ee) were obtained in the hydrogenation of enamides.
- Zeng, Qing-Heng,Hu, Xiang-Ping,Duan, Zheng-Chao,Liang, Xin-Miao,Zheng, Zhuo
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p. 1233 - 1238
(2007/10/03)
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- Chiral diphosphine ligands based on camphor: Synthesis and applications in asymmetric hydrogenations
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The synthesis of a novel class of atropisomer chiral diphosphine ligands with a bornene framework is described. The new ligands showed in Rh catalyzed asymmetric hydrogenation of α- and β-enamides very high ee's (more than 99%).
- Kadyrov, Renat,Ilaldinov, Ilyas Z.,Almena, Juan,Monsees, Axel,Riermeier, Thomas H.
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p. 7397 - 7400
(2007/10/03)
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