- Unmasking the Hidden Carbonyl Group Using Gold(I) Catalysts and Alcohol Dehydrogenases: Design of a Thermodynamically-Driven Cascade toward Optically Active Halohydrins
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A concurrent cascade combining the use of a gold(I) N-heterocyclic carbene (NHC) and an alcohol dehydrogenase (ADH) is disclosed for the synthesis of highly valuable enantiopure halohydrins in an aqueous medium and under mild reaction conditions. The meth
- Escot, Lorena,González-Granda, Sergio,Gotor-Fernández, Vicente,Lavandera, Iván
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p. 2552 - 2560
(2022/02/16)
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- Electro-mediated PhotoRedox Catalysis for Selective C(sp3)–O Cleavages of Phosphinated Alcohols to Carbanions
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We report a novel example of electro-mediated photoredox catalysis (e-PRC) in the reductive cleavage of C(sp3)?O bonds of phosphinated alcohols to alkyl carbanions. As well as deoxygenations, olefinations are reported which are E-selective and can be made Z-selective in a tandem reduction/photosensitization process where both steps are photoelectrochemically promoted. Spectroscopy, computation, and catalyst structural variations reveal that our new naphthalene monoimide-type catalyst allows for an intimate dispersive precomplexation of its radical anion form with the phosphinate substrate, facilitating a reactivity-determining C(sp3)?O cleavage. Surprisingly and in contrast to previously reported photoexcited radical anion chemistries, our conditions tolerate aryl chlorides/bromides and do not give rise to Birch-type reductions.
- Barham, Joshua P.,K?nig, Burkhard,Karl, Tobias A.,Reiter, Sebastian,Tian, Xianhai,Yakubov, Shahboz,de Vivie-Riedle, Regina
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supporting information
p. 20817 - 20825
(2021/08/18)
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- Deep Eutectic Solvents as Media in Alcohol Dehydrogenase-Catalyzed Reductions of Halogenated Ketones
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The application of deep eutectic solvents (DESs) in biotechnological processes has gained an outstanding relevance, as they can be used as greener media to obtain higher productivities and selectivities. In the present contribution, an eutectic mixture composed of choline chloride (ChCl): glycerol (1 : 2 mol/mol) has been used as a reaction medium in combination with Tris?SO4 50 mM buffer pH 7.5, applied to the alcohol dehydrogenase (ADH)-catalyzed reduction of various carbonyl precursors of chiral halohydrins. These alcohols are key intermediates of biologically active compounds, and hence they are of industrial interest. In the presence of up to 50 % v/v of DES, these biotransformations were achieved up to 300–400 mM of the α-halogenated ketone substrate, getting access to the final compounds with excellent conversions (usually >90 %) and enantiomeric excess (ee >99 %). Among the different ADHs tested, two stereocomplementary enzymes (Lactobacillus brevis ADH and Rhodococcus ruber ADH) afforded the best results, so both alcohol enantiomers could be obtained in all the studied examples. Selected bioreductions were scaled up to 250 mg and 1 g, demonstrating the potential that DESs can offer as media in redox processes for substrates with low solubility in water.
- Ibn Majdoub Hassani, Fatima Zohra,Amzazi, Saaid,Kreit, Joseph,Lavandera, Iván
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p. 832 - 836
(2019/12/24)
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- Lipase mediated enzymatic kinetic resolution of phenylethyl halohydrins acetates: A case of study and rationalization
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Racemic phenylethyl halohydrins acetates containing several groups attached to the aromatic ring were resolved via hydrolysis reaction in the presence of lipase B from Candida antarctica (Novozym 435). In all cases, the kinetic resolution was highly selective (E > 200) leading to the corresponding (S)-β-halohydrin with ee > 99 %. However, the time required for an ideal 50 % conversion ranged from 15 min for 2,4-dichlorophenyl chlorohydrin acetate to 216 h for 2-chlorophenyl bromohydrin acetate. Six chlorohydrins and five bromohydrins were evaluated, the latter being less reactive. For the β-brominated substrates, steric hindrance on the aromatic ring played a crucial role, which was not observed for the β-chlorinated derivatives. To shed light on the different reaction rates, docking studies were carried out with all the substrates using MD simulations. The computational data obtained for the β-brominated substrates, based on the parameters analysed such as NAC (near attack conformation), distance between Ser-O and carbonyl-C and oxyanion site stabilization were in agreement with the experimental results. On the other hand, the data obtained for β-chlorinated substrates suggested that physical aspects such as high hydrophobicity or induced change in the conformation of the enzymatic active site are more relevant aspects when compared to steric hindrance effects.
- Fonseca, Thiago de Sousa,Vega, Kimberly Benedetti,da Silva, Marcos Reinaldo,de Oliveira, Maria da Concei??o Ferreira,de Lemos, Telma Leda Gomes,Contente, Martina Letizia,Molinari, Francesco,Cespugli, Marco,Fortuna, Sara,Gardossi, Lucia,de Mattos, Marcos Carlos
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- Organomagnesium Based Flash Chemistry: Continuous Flow Generation and Utilization of Halomethylmagnesium Intermediates
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The generation of highly unstable chloromethylmagnesium chloride in a continuous flow reactor and its reaction with aldehydes and ketones is reported. With this strategy, chlorohydrins and epoxides were synthesized within a total residence time of only 2.6 s. The outcome of the reaction can be tuned by simply using either a basic or an acidic quench. Very good to excellent isolated yields, up to 97%, have been obtained for most cases (30 examples).
- Von Keutz, Timo,Cantillo, David,Kappe, C. Oliver
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supporting information
p. 7537 - 7541
(2020/10/12)
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- A new entry of highly selective and nucleophilic BrH2C-and CLH2c-titanium complexes for carbonyl coupling
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The direct coupling of various aldehydes and ketones with CH2Br2 or CH2Cl2 promoted by TiCl4-Mg bimetallic complex provides an extremely simple, practical, and efficient approach for the construction of bromomethyl or chloromethyl carbinols. The high chemoselectivity of this chemistry is illus-trated by the TiCl4-Mg-promoted selective coupling of CH2Br2 or CH2Cl2 with an aldehyde in the presence of ketone and selective transfer of CH2Br or CH2Cl to saturated carbonyl moiety. This protocol is also suitable for sterically hindered and enoliza-ble carbonyl compounds.
- Yan, Tu Hsin,Ananthan, Bakthavachalam,Chang, Su Haur
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p. 778 - 787
(2019/01/24)
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- Iridium-Catalyzed Asymmetric Hydrogenation of Halogenated Ketones for the Efficient Construction of Chiral Halohydrins
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Iridium-catalyzed asymmetric hydrogenation of prochiral halogenated ketones was successfully developed to prepare various chiral halohydrins with high reactivities and excellent enantioselectivities under basic reaction condition (up to >99% conversion, 99% yield, >99% ee). Moreover, gram-scale experiment was performed well in the presence of just 0.005 mol% (S/C=20 000) Ir/f-amphox catalyst with 99% yield and >99% ee. (Figure presented.).
- Yin, Congcong,Wu, Weilong,Hu, Yang,Tan, Xuefeng,You, Cai,Liu, Yuanhua,Chen, Ziyi,Dong, Xiu-Qin,Zhang, Xumu
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supporting information
p. 2119 - 2124
(2018/04/30)
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- Ultrafast Iron-Catalyzed Reduction of Functionalized Ketones: Highly Enantioselective Synthesis of Halohydrines, Oxaheterocycles, and Aminoalcohols
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A molecularly defined chiral boxmi iron alkyl complex catalyzes the hydroboration of various functionalized ketones and provides the corresponding chiral halohydrines, oxaheterocycles (oxiranes, oxetanes, tetrahydrofurans, and dioxanes) and amino alcohols with excellent enantioselectivities (up to >99 %ee) and conversion efficiencies at low catalyst loadings (as low as 0.5 mol %). Turnover frequencies of greater than 40000 h?1 at ?30 °C highlight the activity of this earth-abundant metal catalyst which tolerates a large number of functional groups.
- Blasius, Clemens K.,Vasilenko, Vladislav,Gade, Lutz H.
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supporting information
p. 10231 - 10235
(2018/07/31)
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- Selective Asymmetric Transfer Hydrogenation of α-Substituted Acetophenones with Bifunctional Oxo-Tethered Ruthenium(II) Catalysts
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A practical method for the asymmetric transfer hydrogenation of α-substituted ketones was developed utilizing oxo-tethered N-sulfonyldiamine-ruthenium complexes. Reduction by HCO2H and HCO2K in a mixed solvent of EtOAc/H2O allowed for the selective synthesis of halohydrins from 2-bromoacetophenone (98%) and 2-chloroacetophenone (>99%), leading to suppressed undesired side reactions stemming from formylation under the typical reaction conditions using an azeotropic 5:2 mixture of HCO2H and Et3N. A range of functional groups, such as halogens, methoxy, nitro, dimethylamino, and ester groups, were well tolerated, highlighting the potential of this method. Nearly complete selectivity with a preferable ee was maintained even with a substrate/catalyst (S/C) ratio of 5000. This catalyst system was also effective for the asymmetric reduction of α-sulfonated ketones without eroding the leaving group. (Figure presented.).
- Yuki, Yamato,Touge, Taichiro,Nara, Hideki,Matsumura, Kazuhiko,Fujiwhara, Mitsuhiko,Kayaki, Yoshihito,Ikariya, Takao
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supporting information
p. 568 - 574
(2017/12/13)
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- Cross-Linked Artificial Enzyme Crystals as Heterogeneous Catalysts for Oxidation Reactions
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Designing systems that merge the advantages of heterogeneous catalysis, enzymology, and molecular catalysis represents the next major goal for sustainable chemistry. Cross-linked enzyme crystals display most of these essential assets (well-designed mesoporous support, protein selectivity, and molecular recognition of substrates). Nevertheless, a lack of reaction diversity, particularly in the field of oxidation, remains a constraint for their increased use in the field. Here, thanks to the design of cross-linked artificial nonheme iron oxygenase crystals, we filled this gap by developing biobased heterogeneous catalysts capable of oxidizing carbon-carbon double bonds. First, reductive O2 activation induces selective oxidative cleavage, revealing the indestructible character of the solid catalyst (at least 30 000 turnover numbers without any loss of activity). Second, the use of 2-electron oxidants allows selective and high-efficiency hydroxychlorination with thousands of turnover numbers. This new technology by far outperforms catalysis using the inorganic complexes alone, or even the artificial enzymes in solution. The combination of easy catalyst synthesis, the improvement of "omic" technologies, and automation of protein crystallization makes this strategy a real opportunity for the future of (bio)catalysis.
- Lopez, Sarah,Rondot, Laurianne,Leprêtre, Chloé,Marchi-Delapierre, Caroline,Ménage, Stéphane,Cavazza, Christine
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supporting information
p. 17994 - 18002
(2017/12/26)
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- Difunctionalization of Alkenes Using 1-Chloro-1,2-benziodoxol-3-(1H)-one
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Difunctionalization of alkenes with 1-chloro-1,2-benziodoxol-3-(1H)-one (1) was investigated. Various additional nucleophiles were tested, and oxychlorination, dichlorination, azidochlorination, chlorothiocyanation, and iodoesterfication were demonstrated. The oxychlorination product was obtained efficiently when the reaction was operated in water. Dichlorination occurred in the presence of a Lewis basic promoter, such as 4-phenylpyridine N-oxide, as an additive. The reaction with in situ-generated azido anion afforded azidochlorinated compounds with a chlorine atom at the terminal position, while the reaction with trimethylsilyl isothiocyanate produced chlorothiocyanation adducts with a chlorine atom at the benzylic position. On the other hand, when 1 was treated with tetra-n-butylammonium iodide prior to the addition of alkenes, only iodoesterification occurred selectively. These mild reactions enable convenient site-selective difunctionalizations of substrates having two alkene moieties. NMR experiments suggested that the electrophilic reactive species in each reaction varied depending on the nature of the added nucleophile.
- Egami, Hiromichi,Yoneda, Takahiro,Uku, Minako,Ide, Takafumi,Kawato, Yuji,Hamashima, Yoshitaka
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p. 4020 - 4030
(2016/06/09)
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- Synthesis of enantiopure epoxide by 'one pot' chemoenzymatic approach using a highly enantioselective dehydrogenase
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Enantiopure α-phenethyl alcohols, including aromatic halohydrins, are important chiral building blocks. One of the best approaches to synthesise α-phenethyl alcohols is asymmetric reduction of prochiral ketones by alcohol dehydrogenases (ADHs). The obtained enantiopure halohydrin could be directly used to produce enantiopure epoxide through a base-induced ring-closure reaction, which is an attractive 'one pot' chemoenzymatic method for producing high-yield epoxide. In this study, a novel medium-chain dehydrogenase (KcDH) from Kuraishia capsulate CBS1993 was identified and characterised to show its broad substrate scope and excellent enantioselectivity. KcDH showed activities on 25 substrates of the 26 tested aromatic ketones and heteroaryl ketones, with an enantiomeric excess (ee) >99% and the highest relative activity observed with para-nitro acetophenone. Due to its high enantioselectivity for α-haloketones, a chemoenzymatic method for the synthesis of enantiopure styrene oxide (SO) and phenyl glycidyl ether (PGE) was developed through a base-induced ring-closure reaction on enantiopure halohydrin obtained with KcDH. (R)-SO and (S)-PGE were obtained in 86% and 94% analytical yield, respectively, and both epoxides were obtained with ee >99%. Thus, our results suggested that KcDH may be a promising biocatalyst for the production of multiple enantiopure α-phenethyl alcohols and epoxides.
- Wu, Kai,Chen, Lifeng,Fan, Haiyang,Zhao, Zhiqiang,Wang, Hualei,Wei, Dongzhi
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p. 899 - 904
(2016/02/05)
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- The vicinal functionalization of olefins: A facile route to the direct synthesis of β-chlorohydrins and β-chloroethers
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An efficient and environmentally benign protocol for the synthesis of vicinal chlorohydroxy and chloromethoxy derivatives in a highly regioselective manner from olefins using NH4Cl as a chlorine source and oxone as an oxidant in aqueous acetone and methanol is demonstrated. This methodology offers an additive and metal chloride free approach and is endowed with simple reaction conditions, high yields a broad substrate scope and good functional group tolerance. Moreover, the aromatic substrates with a terminal double bond exhibited merely Markovnikov selectivity, while the internal alkenes show exclusive regiocontrol and low to moderate diastereoselectivity.
- Swamy, Peraka,Kumar, Macharla Arun,Reddy, Marri Mahender,Naresh, Mameda,Srujana, Kodumuri,Narender, Nama
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p. 26288 - 26294
(2014/07/08)
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- Versatile iridicycle catalysts for highly efficient and chemoselective transfer hydrogenation of carbonyl compounds in water
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Cyclometalated iridium complexes are shown to be highly efficient and chemoselective catalysts for the transfer hydrogenation of a wide range of carbonyl groups with formic acid in water. Examples include α-substituted ketones (α-ether, α-halo, α-hydroxy, α-amino, α-nitrile or α-ester), α-keto esters, β-keto esters and α,β-unsaturated aldehydes. The reduction was carried out at substrate/catalyst ratios of up to 50000 at pH 4.5 and required no organic solvent. The protocol provides a practical, easy and efficient way for the synthesis of β-functionalised secondary alcohols, such as β-hydroxyethers, β-hydroxyamines and β-hydroxyhalo compounds, which are valuable intermediates in pharmaceutical, fine chemical, perfume and agrochemical synthesis. Water wonder: Iridicycle catalysts are versatile and allow the highly efficient and chemoselective transfer hydrogenation of a variety of carbonyl compounds, including problematic and challenging ones, with formate in neat water (see scheme).
- Talwar, Dinesh,Wu, Xiaofeng,Saidi, Ourida,Salguero, Noemí Poyatos,Xiao, Jianliang
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supporting information
p. 12835 - 12842
(2015/03/30)
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- 2-(2-Phenylmorpholin-4-yl)pyrimidin-4(3H)-ones; A new class of potent, selective and orally active glycogen synthase kinase-3β inhibitors
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A series of 2-(2-phenylmorpholin-4-yl)pyrimidin-4(3H)-ones was synthesized and examined for their inhibitory activity against glycogen synthase kinase-3β (GSK-3β). We found 21, 29 and 30 to possess potent in vitro GSK-3β inhibitory activity with good in vitro PK profiles. 21 demonstrated significant decrease of tau phosphorylation after oral administration in mice and excellent PK profiles.
- Fukunaga, Kenji,Uehara, Fumiaki,Aritomo, Keiichi,Shoda, Aya,Hiki, Shinsuke,Okuyama, Masahiro,Usui, Yoshihiro,Watanabe, Kazutoshi,Yamakoshi, Koichi,Kohara, Toshiyuki,Hanano, Tokushi,Tanaka, Hiroshi,Tsuchiya, Susumu,Sunada, Shinji,Saito, Ken-Ichi,Eguchi, Jun-Ichi,Yuki, Satoshi,Asano, Shoichi,Tanaka, Shinji,Mori, Akiko,Yamagami, Keiji,Baba, Hiroshi,Horikawa, Takashi,Fujimura, Masatake
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p. 6933 - 6937
(2014/01/06)
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- Multi-enzymatic biosynthesis of chiral β-hydroxy nitriles through co-expression of oxidoreductase and halohydrin dehalogenase
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To establish a system for the efficient one bacterial multi-enzymatic biosynthesis of both (R)- and (S)-β-hydroxy nitriles, we co-expressed alcohol dehydrogenases with opposite stereoselectivities, cofactor regeneration enzymes, and a halohydrin dehalogenase in Escherichia coli. By researching cofactor recycling and various co-expression strategies and by selecting and engineering the halohydrin dehalogenase, we engineered two E. coli strains, which were subsequently used in a cascade of reactions to produce chiral β-hydroxy nitriles with high enantiomeric excess directly from prochiral α-halo ketones. Three valuable pharmaceutical intermediates were prepared by means of this catalytic system, and substrate conversion reached about >99%. More importantly, the system is of low cost because there is no need for expensive cofactors or for expression and purification of the component enzymes. Copyright
- Chen, Shao-Yun,Yang, Chen-Xi,Wu, Jian-Ping,Xu, Gang,Yang, Li-Rong
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p. 3179 - 3190
(2013/12/04)
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- Highly regio- and diastereoselective halohydroxylation of olefins: A facile synthesis of vicinal halohydrins
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An efficient method for the synthesis of vicinal chlorohydrin or bromohydrin derivatives has been developed on the basis of direct halohydroxylation of various olefins with electrondonating or withdrawing substituent. The reactions were carried out under mild conditions in the presence of N-tosyl-l-threonine (NTsLT) as an acidic additive using chloramine T trihydrate, 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) or N-bromoacetamide (AcNHBr) as the halogen source, respectively, affording the corresponding vicinal halohydrins in good to high yields with excellent regio- and stereoselectivities.
- Zhang, Jinglei,Wang, Jie,Qiu, Zhuibai,Wang, Yang
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experimental part
p. 6859 - 6867
(2011/10/02)
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- Asymmetric borane reduction of prochiral ketones catalyzed by C3-symmetric sulfonamide
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A novel, recoverable, C3-symmetric sulfonamide L-1 has been developed for the asymmetric borane reduction of prochiral ketones in refluxing THF. The optically active secondary alcohols were obtained in excellent enantiometric excesses (up to 97% ee) and good yields. The C3-symmetric sulfonamide L-1 can be easily recovered and reused four times without any significant loss of catalytic activity.
- Li, Gao-Qiang,Yan, Ze-Yi,Niu, Yan-Ning,Wu, Lu-Yong,Wei, Hai-Long,Liang, Yong-Min
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p. 816 - 821
(2008/09/19)
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- Highly efficient route for enantioselective preparation of chlorohydrins via dynamic kinetic resolution
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(Equation Presented) Dynamic kinetic resolution (DKR) of various aromatic chlorohydrins with the use of Pseudomonas cepacia lipase (PS-C "Amano" II) and ruthenium catalyst 1 afforded chlorohydrin acetates in high yields and high enantiomeric excesses. These optically pure chlorohydrin acetates are useful synthetic intermediates and can be transformed to a range of important chiral compounds.
- Traeft, Annika,Bogar, Krisztian,Warner, Madeleine,Baeckvall, Jan-E.
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supporting information; experimental part
p. 4807 - 4810
(2009/05/31)
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- Sulfonate Catalyst and Method of Producing Alcohol Compound Using the Same
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A sulfonate catalyst represented by the formula below and a ketone compound are placed in a solvent, and the ketone compound is hydrogenated by mixing in the presence of hydrogen to produce an optically active alcohol.
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Page/Page column 8
(2008/12/07)
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- Asymmetric transfer hydrogenation over Ru-TsDPEN catalysts supported on siliceous mesocellular foam
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A siliceous mesocellular foam-immobilized Ru-TsDPEN complex exhibited excellent catalytic reactivity, enantioselectivity and reusability in the asymmetric transfer hydrogenation of an imine and ketones. The Royal Society of Chemistry.
- Huang, Xiaohua,Ying, Jackie Y.
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p. 1825 - 1827
(2008/01/03)
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- Asymmetric hydrogenation of α-chloro aromatic ketones catalyzed by η6-arene/TsDPEN-ruthenium(II) complexes
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(Chemical Equation Presented) Asymmetric hydrogenation of various α-chloro aromatic ketones with Ru(OTf)(TsDPEN)(η6-arene) (TsDPEN = N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine) produces the chiral chlorohydrins in up to 98% ee. This reac
- Ohkuma, Takeshi,Tsutsumi, Kunihiko,Utsumi, Noriyuki,Arai, Noriyoshi,Noyori, Ryoji,Murata, Kunihiko
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p. 255 - 257
(2007/10/03)
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- An investigation into the tether length and substitution pattern of arene-substituted complexes for asymmetric transfer hydrogenation of ketones
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(Figure Presented) A series of Ru(II) catalysts were prepared and tested in the asymmetric transfer hydrogenation of ketones. The catalyst containing a "4-carbon" tether gave the fastest rates of ketone reduction. This is due to both increased rate of reg
- Cheung, Fung K.,Lin, Changxue,Minissi, Franco,Criville, Adriana Lorente,Graham, Mark A.,Fox, David J.,Wills, Martin
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p. 4659 - 4662
(2008/03/12)
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- PROCESS FOR PRODUCTION OF OPTICALLY ACTIVE ALCOHOLS
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A ruthenium complex RuCl[(S,S)-Tsdpen](p-cymene) represented by a formula below and a ketone compound are placed in a polar solvent, and the resulting mixture is mixed under pressurized hydrogen to hydrogenate the ketone compound and to thereby produce an optically active alcohol:
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Page/Page column 12
(2008/06/13)
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- Asymmetric borane reduction of prochiral ketones using imidazolium-tagged sulfonamide catalyst
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A novel sulfonamide catalyst based on a room temperature ionic liquid (RTIL) has been developed for the enantioselective reduction of ketones in refluxing toluene. The optically active secondary alcohol products were obtained in good enantiomeric excess and excellent yields. The imidazolium-tagged sulfonamide catalyst can be readily recovered and reused four times without any significant loss of catalytic activity.
- Yang, Shang-Dong,Shi, Yun,Sun, Zhen-Hua,Zhao, Ya-Bin,Liang, Yong-Min
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p. 1895 - 1900
(2007/10/03)
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- A practical synthesis of optically active aromatic epoxides via asymmetric transfer hydrogenation of α-chlorinated ketones with chiral rhodium-diamine catalyst
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A practical method for the synthesis of optically active aromatic epoxides has been developed via the formation of optically active α-chlorinated alcohols and intramolecular etherification. Optically active alcohols with up to 99% ee can be obtained from
- Hamada, Takayuki,Torii, Takayoshi,Izawa, Kunisuke,Ikariya, Takao
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p. 7411 - 7417
(2007/10/03)
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- Highly catalytic enantioselective reduction of aromatic ketones using chiral polymer-supported Corey, Bakshi, and Shibata catalysts
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A systematic study was conducted to formulate the optimal reaction parameters for polymer-supported (PS)-oxazaborolidine catalyzed enantioselective ketone reduction. The B-methylated chiral oxazaborolidine prepared in situ from the previously reported polymers by Degni et al. have been used in the enantioselective borane reduction of some substituted aromatic ketones to afford the corresponding optical active secondary alcohol products. While the linear-bound system shows low enantioselectivity, the cross-linked version affords enantioselectivities almost identical to those of the monomeric model (with up to 96% enantiomeric excesses).
- Degni, Sylvestre,Wilen, Carl-Eric,Rosling, Ari
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p. 1495 - 1499
(2007/10/03)
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- PROCESS FOR PRODUCING OPTICALLY ACTIVE HALOHYDRIN COMPOUND
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A process of preparing an optically active halohydrin compound characterized by comprising asymmetric hydrogen transfer reduction of an α-haloketone compound in the presence of a group 9 transition metal compound having a substituted or unsubstituted cyclopentadienyl group and an optically active diamine compound. The asymmetric hydrogen transfer reduction is preferably conducted in the presence of a base.
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- Chemoenzymatic dynamic kinetic resolution of β-halo alcohols. An efficient route to chiral epoxides
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Enzymatic resolution of β-chloro alcohols in combination with ruthenium-catalyzed alcohol isomerization led to a successful dynamic kinetic resolution (conversion up to 99% and ee up to 97%). The efficiency of the DKR is dramatically reduced when β-bromo alcohols are used. The presence of the bromo substituent causes decomposition of the ruthenium catalysts, which triggers the progressive deactivation of the enzyme. The synthetic utility of this procedure has been illustrated by the practical synthesis of different chiral epoxides.
- Pamies, Oscar,Baeckvall, Jan-E.
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p. 9006 - 9010
(2007/10/03)
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- Practical synthesis of optically active styrene oxides via reductive transformation of 2-chloroacetophenones with chiral rhodium catalysts
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(equation presented) A practical method for the synthesis of optically active styrene oxides has been developed via formation of optically active 2-chloro-1-phenylethanols generated by reductive transformation of ring-substituted 2-chloroacetophenones. Th
- Hamada, Takayuki,Torii, Takayoshi,Izawa, Kunisuke,Noyori, Ryoji,Ikariya, Takao
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p. 4373 - 4376
(2007/10/03)
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- anti-Prelog microbial reduction of aryl α-halomethyl or α- hydroxymethyl ketones with Geotrichum sp. 38
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Reduction of aryl α-halomethyl ketones 5a-d and 7a-h and α- hydroxymethyl ketones 10a-b by Geotrichum sp. 38 affording mostly the anti- Prelog alcohols was reported and the stereoselectivities of the reductive products were discussed.
- Wei, Zhi-Liang,Li, Zu-Yi,Lin, Guo-Qiang
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p. 13059 - 13072
(2007/10/03)
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- Process for the preparation of optically active 2-halo-1-(substituted phenyl) ethanol
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The present invention provides an industrially advantageous process for the preparation of an optically active 2-halo-1-(substituted phenyl)ethanol useful as medicines, agricultural chemicals or as intermediates thereof; and a simple process for the prepa
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- Microbial reduction of 2-chloro-3-aryl-3-oxopropionic acid esters
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2-Chloro-3-aryl-3-oxopropionic acid esters are reduced by microorganisms to syn- and/or anti-2-chloro-3-hydroxy-3-arylpropionates, in competition with dechlorination and decarboxylation reactions. Using selected strains, it is possible to obtain enantiomerically pure chlorohydroxyesters, which were converted to the corresponding phenylglycidic esters with high stereospecificity.
- Cabon,Larcheveque,Buisson,Azerad
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p. 7337 - 7340
(2007/10/02)
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