- A Mass Spectral Investigation of Water and Acetic Acid Elimination From 1- and 2-Indan Derivatives
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Water and acetic acid eliminations from 1- and 2-indan derivatives have been investigated.Deuterium labeling, high resolution peak matching and the metastable peak analysis capabilities of a high resolution triple analyzer (E B E) mass spectrometer were employed to examine the eliminations.These experiments showed that water was lost from 1-indanol via 1,2 and 1,3 processes.These results contrast with those obtained for 1-tetralol, which specifically eliminates water in a 1,4 process involving the benzylic hydrogens.Water elimination from 2-indanol is preceded by a slow hydroxyl-benzylic hydrogen exchange and proceeds specifically 1,2.Water losses from both 1- and 2-indanol are characterized by large kinetic energy releases.Acetic acid elimination is shown to occur specifically 1,3 from 1-acetoxyindan and 1,2 from 2-acetoxyindan.
- Groenewold, G. S.,Gross, M. L.,Zey, R.
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Read Online
- Selective deprotection of alkyl t-butyldimethylsilyl ethers in the presence of aryl t-butyldimethylsilyl ethers with bismuth bromide
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Alkyl t-butyldimethylsilyl ethers can be selectively cleaved in the presence of aryl ethers using a catalytic amount of bismuth bromide in wet acetonitrile at ambient temperatures. (C) 2000 Elsevevier Science Ltd.
- Bajwa,Vivelo,Slade,Repic,Blacklock
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Read Online
- Erbium-Catalyzed Regioselective Isomerization-Cobalt-Catalyzed Transfer Hydrogenation Sequence for the Synthesis of Anti-Markovnikov Alcohols from Epoxides under Mild Conditions
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Herein, we report an efficient isomerization-transfer hydrogenation reaction sequence based on a cobalt pincer catalyst (1 mol %), which allows the synthesis of a series of anti-Markovnikov alcohols from terminal and internal epoxides under mild reaction conditions (≤55 °C, 8 h) at low catalyst loading. The reaction proceeds by Lewis acid (3 mol % Er(OTf)3)-catalyzed epoxide isomerization and subsequent cobalt-catalyzed transfer hydrogenation using ammonia borane as the hydrogen source. The general applicability of this methodology is highlighted by the synthesis of 43 alcohols from epoxides. A variety of terminal (23 examples) and 1,2-disubstituted internal epoxides (14 examples) bearing different functional groups are converted to the desired anti-Markovnikov alcohols in excellent selectivity and yields of up to 98%. For selected examples, it is shown that the reaction can be performed on a preparative scale up to 50 mmol. Notably, the isomerization step proceeds via the most stable carbocation. Thus, the regiochemistry is controlled by stereoelectronic effects. As a result, in some cases, rearrangement of the carbon framework is observed when tri-and tetra-substituted epoxides (6 examples) are converted. A variety of functional groups are tolerated under the reaction conditions even though aldehydes and ketones are also reduced to the respective alcohols under the reaction conditions. Mechanistic studies and control experiments were used to investigate the role of the Lewis acid in the reaction. Besides acting as the catalyst for the epoxide isomerization, the Lewis acid was found to facilitate the dehydrogenation of the hydrogen donor, which enhances the rate of the transfer hydrogenation step. These experiments additionally indicate the direct transfer of hydrogen from the amine borane in the reduction step.
- Liu, Xin,Longwitz, Lars,Spiegelberg, Brian,T?njes, Jan,Beweries, Torsten,Werner, Thomas
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p. 13659 - 13667
(2020/11/30)
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- Efficient Transfer Hydrogenation of Ketones using Methanol as Liquid Organic Hydrogen Carrier
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Herein, we demonstrate an efficient protocol for transfer hydrogenation of ketones using methanol as practical and useful liquid organic hydrogen carrier (LOHC) under Ir(III) catalysis. Various ketones, including electron-rich/electron-poor aromatic ketones, heteroaromatic and aliphatic ketones, have been efficiently reduced into their corresponding alcohols. Chemoselective reduction of ketones was established in the presence of various other reducible functional groups under mild conditions.
- Garg, Nidhi,Paira, Soumen,Sundararaju, Basker
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p. 3472 - 3476
(2020/05/29)
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- A General Method for Photocatalytic Decarboxylative Hydroxylation of Carboxylic Acids
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A general and practical method for decarboxylative hydroxylation of carboxylic acids was developed through visible light-induced photocatalysis using molecular oxygen as the green oxidant. The addition of NaBH4 to in situ reduce the unstable peroxyl radical intermediate much broadened the substrate scope. Different sp3 carbon-bearing carboxylic acids were successfully employed as substrates, including phenylacetic acid-type substrates, as well as aliphatic carboxylic acids. This transformation worked smoothly on primary, secondary, and tertiary carboxylic acids.
- Khan, Shah Nawaz,Zaman, Muhammad Kashif,Li, Ruining,Sun, Zhankui
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p. 5019 - 5026
(2020/05/01)
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- Direct Photorelease of Alcohols from Boron-Alkylated BODIPY Photocages
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BODIPY photocages allow the release of substrates using visible light irradiation. They have the drawback of requiring reasonably good leaving groups for photorelease. Photorelease of alcohols is often accomplished by attachment with carbonate linkages, which upon photorelease liberate CO2 and generate the alcohol. Here, we show that boron-alkylated BODIPY photocages are capable of directly photoreleasing both aliphatic alcohols and phenols upon irradiation via photocleavage of ether linkages. Direct photorelease of a hydroxycoumarin dye was demonstrated in living HeLa cells.
- Fischer, Logan J.,Gehrmann, Elizabeth J.,Peterson, Julie A.,Shrestha, Pradeep,Smith, Emily A.,Wijesooriya, Chamari S.,Winter, Arthur H.,Yuan, Ding
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supporting information
p. 5712 - 5717
(2020/05/19)
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- Method for carrying out reduction on aldehyde and ketone to obtain alcohol
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The invention discloses a method for carrying out reduction on aldehyde and ketone to obtain alcohol. Tri-(pentafluorobenzene-base) borane is used as a catalyst, and hydrogen silane is used as a reducing agent. The method includes adding water into reaction systems and carrying out reduction on the aldehyde or the ketone under the normal-temperature condition to obtain the corresponding alcohol. Compared with the prior art, the method has the advantages that reaction can be quickly carried out under the normal-temperature and normal-pressure conditions, the reaction conditions are mild, the method is high in reaction efficiency, and the yield is 95%-100% as shown by 1H NMR (1H nuclear magnetic resonance) detection; the water can be used as a solvent used in the reaction, and accordingly the method is low in cost and little in pollution; the catalyst and the reducing agent do not contain heavy metal, and accordingly the problem of heavy metal pollution and the like can be solved by theaid of the method.
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Paragraph 0019; 0020; 0042; 0043
(2019/03/30)
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- Photoinduced electron transfer-promoted reactions using exciplex-type organic photoredox catalyst directly linking donor and acceptor arenes
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Directly linked donor and acceptor arenes, such as phenanthrene/naphthalene/biphenyl and 1,3-dicyanobenzene were found to work as photoredox catalysts in the photoreactions of indene, 2,3-dimethyl-2-butene, and 4-methoxyphenylacetic acid. The new stable organic photocatalyst forms an intramolecular exciplex (excited complex) when irradiated in a polar solvent and shows redox catalyst activity, even at low concentrations. To the best of our knowledge, this is the first example of an intramolecular exciplex working as a redox catalyst.
- Yamawaki, Mugen,Asano, Akiko,Furutani, Toshiki,Izumi, Yuki,Tanaka, Yosuke,Osaka, Kazuyuki,Morita, Toshio,Yoshimi, Yasuharu
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- Iridium-promoted conversion of terminal epoxides to primary alcohols under acidic conditions using hydrogen
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A strategy for the conversion of terminal epoxides to primary alcohols is presented. The reaction uses hydrogen as the only stoichiometric reagent and is promoted by an iridium precatalyst under acidic conditions. Selectivity for the formation of a terminal alcohol over an internal alcohol is observed for both alkyl- and aryl-substituted terminal epoxides in isolated yields of up to 50% and 72% respectively.
- Rainsberry, Alena N.,Sage, Jarrod G.,Scheuermann, Margaret L.
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p. 3020 - 3022
(2019/06/27)
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- Reliably Regioselective Dialkyl Ether Cleavage with Mixed Boron Trihalides
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A protocol for the regioselective cleavage of unsymmetrical alkyl ethers to generate alkyl alcohol and alkyl bromide products is described. A mixture of trihaloboranes triggers this conversion and exhibits improved reactivity profiles (regioselectivity and yield) compared with BBr3 alone. Additionally, this procedure allows the efficient synthesis of (B-Cl) dialkyl boronate esters. There are limited methods to generate acyclic dialkoxyboryl chlorides, and these intermediates constitute important synthons in main-group chemistry.
- Atienza, Bren Jordan P.,Truong, Nam,Williams, Florence J.
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p. 6332 - 6335
(2018/10/09)
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- Visible-Light-Mediated Aerobic Oxidation of Organoboron Compounds Using in Situ Generated Hydrogen Peroxide
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A simple and general visible-light-mediated oxidation of organoboron compounds has been developed with rose bengal as the photocatalyst, substoichiometric Et3N as the electron donor, as well as air as the oxidant. This mild and metal-free protocol shows a broad substrate scope and provides a wide range of aliphatic alcohols and phenols in moderate to excellent yields. Notably, the robustness of this method is demonstrated on the stereospecific aerobic oxidation of organoboron compounds.
- Weng, Wei-Zhi,Liang, Hao,Zhang, Bo
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p. 4979 - 4983
(2018/08/24)
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- (Poly)cationic λ3-Iodane-Mediated Oxidative Ring Expansion of Secondary Alcohols
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Herein, a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ3-iodanes (N-HVIs) is reported. Excellent levels of selectivity are achieved for C–O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N-HVI. The resulting hexafluoroisopropanol (HFIP) acetals are readily derivatized with a range of nucleophiles, providing a versatile functional handle for subsequent manipulations. The utility of this methodology for late-stage natural product derivatization was also demonstrated, providing a new tool for diversity-oriented synthesis and complexity-to-diversity (CTD) efforts. Preliminary mechanistic investigations reveal a strong effect of alcohol conformation on the reactive pathway, thus providing a predictive power in the application of this approach to complex molecule synthesis.
- Walters, Jennifer C.,Tierno, Anthony F.,Dubin, Aimee H.,Wengryniuk, Sarah E.
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supporting information
p. 1460 - 1464
(2018/04/06)
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- Multiple Halogenation of Aliphatic C?H Bonds within the Hofmann–L?ffler Manifold
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An innovative approach to position-selective polyhalogenation of aliphatic hydrocarbon bonds is presented. The reaction proceeded within the Hofmann-L?ffler manifold with amidyl radicals as the sole mediators to induce selective 1,5- and 1,6-hydrogen-atom transfer followed by halogenation. Multiple halogenation events of up to four innate C?H bond functionalizations were accomplished. The broad applicability of this new entry into polyhalogenation and the resulting synthetic possibilities were demonstrated for a total of 27 different examples including mixed halogenations.
- Del Castillo, Estefanía,Martínez, Mario D.,Bosnidou, Alexandra E.,Duhamel, Thomas,O'Broin, Calvin Q.,Zhang, Hongwei,Escudero-Adán, Eduardo C.,Martínez-Belmonte, Marta,Mu?iz, Kilian
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supporting information
p. 17225 - 17229
(2018/11/10)
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- Visible-Light-Mediated Anti-Markovnikov Hydration of Olefins
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Considering that stoichiometric borane and oxidant are required in the classical alkene anti-Markovnikov hydration process, it remains appealing to achieve the transformation in a catalytic protocol. Herein, a visible-light-mediated anti-Markovnikov addition of water to alkenes by using an organic photoredox catalyst in conjunction with a redox-active hydrogen atom donor was developed, which avoided the need for a transition-metal catalyst, stoichiometric borane, as well as oxidant. Both terminal and internal olefins are readily accommodated in this transformation to obtain corresponding primary and secondary alcohols in good yields with single regioselectivity. This procedure can be scaled up to gram scale with a 230 turnover number based on photocatalyst.
- Hu, Xia,Zhang, Guoting,Bu, Faxiang,Lei, Aiwen
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p. 1432 - 1437
(2017/08/09)
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- BTK INHIBITOR
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Provided are a series of BTK inhibitors, and specifically disclosed are a compound, pharmaceutically acceptable salt thereof, tautomer thereof or prodrug thereof represented by formula (I), (II), (III) or (IV).
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Paragraph 1285-1286
(2017/11/16)
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- Bis(silylenyl)-substituted ferrocene-stabilized η6-arene iron(0) complexes: Synthesis, structure and catalytic application
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Reaction of FeX2(thf)n (X = Cl n = 1.5, Br n = 2) with the chelating 1,1′-bis(silylenyl)-substituted ferrocene ligand SiFcSiA (Fc = ferrocendiyl, Si = PhC(NtBu)2Si:) furnishes the corresponding dihalido Fe(ii) complexes [(SiFcSi)FeX2] (X = Cl, 1 and X = Br, 2) in high yields. Reduction of the latter with an excess of KC8 in the presence of benzene and toluene leads to the unprecedented bis(silylene) stabilized Fe0 complexes [(SiFcSi)Fe-η6(C6H6)] 3 and [(SiFcSi)Fe-η6(C7H8)] 4, respectively. The 57Fe M?ssbauer spectrum of 3 at 13 K exhibits parameters (σ = 0.3676 mm s-1; ΔEQ = 1.334 mm s-1) which are consistent with the presence of a pentacoordinated Fe0 atom in a pseudo trigonal-bipyramidal coordination environment, with two dative Si→Fe bonds and three coordination sites occupied by the η6-coordinated arene ligand. Results from DFT calculations, 57Fe M?ssbauer parameters and the diamagnetic NMR spectra confirm the redox-innocent nature of these ligands and the zero oxidation state of the iron center. The catalytic ability of 3 was investigated with respect to ketone hydrogenation. In all cases, good to excellent yields to the corresponding alcohols were obtained at 50 °C and 50 bar H2 pressure. Electron-donating as well as -withdrawing substituents were tolerated with excellent to good yields. Conversions of bulkier ketones and unactivated aliphatic ketones lead merely to moderate yields. This represents the first example of a silylene-iron metal complex which has been utilized as a highly active precatalyst in the hydrogenation of ketones. The results underline the powerful ability of chelating bis(N-heterocyclic silylene) ligands acting as strong σ-donor ligands in stabilizing a new generation of low-valent, electron-rich transition metal complexes for catalytic transformations.
- Luecke, Marcel-Philip,Porwal, Digvijay,Kostenko, Arseni,Zhou, Yu-Peng,Yao, Shenglai,Keck, Matthias,Limberg, Christian,Oestreich, Martin,Driess, Matthias
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supporting information
p. 16412 - 16418
(2017/12/15)
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- O-alkylhydroxylamines as rationally-designed mechanism-based inhibitors of indoleamine 2,3-dioxygenase-1
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Indoleamine 2,3-dioxygenase-1 (IDO1) is a promising therapeutic target for the treatment of cancer, chronic viral infections, and other diseases characterized by pathological immune suppression. Recently important advances have been made in understanding IDO1's catalytic mechanism. Although much remains to be discovered, there is strong evidence that the mechanism proceeds through a heme-iron bound alkylperoxy transition or intermediate state. Accordingly, we explored stable structural mimics of the alkylperoxy species and provide evidence that such structures do mimic the alkylperoxy transition or intermediate state. We discovered that O-benzylhydroxylamine, a commercially available compound, is a potent sub-micromolar inhibitor of IDO1. Structure-activity studies of over forty derivatives of O-benzylhydroxylamine led to further improvement in inhibitor potency, particularly with the addition of halogen atoms to the meta position of the aromatic ring. The most potent derivatives and the lead, O-benzylhydroxylamine, have high ligand efficiency values, which are considered an important criterion for successful drug development. Notably, two of the most potent compounds demonstrated nanomolar-level cell-based potency and limited toxicity. The combination of the simplicity of the structures of these compounds and their excellent cellular activity makes them quite attractive for biological exploration of IDO1 function and antitumor therapeutic applications.
- Malachowski, William P.,Winters, Maria,DuHadaway, James B.,Lewis-Ballester, Ariel,Badir, Shorouk,Wai, Jenny,Rahman, Maisha,Sheikh, Eesha,LaLonde, Judith M.,Yeh, Syun-Ru,Prendergast, George C.,Muller, Alexander J.
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supporting information
p. 564 - 576
(2016/01/09)
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- CATALYTIC HYDROGENATION USING COMPLEXES OF BASE METALS WITH TRIDENTATE LIGANDS
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Complexes of cobalt and nickel with tridentate ligand PNHPR are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHPCy)Co(CH2SiMe3)]BArF4 (PNHPCy=bis[2-(dicyclohexylphosphino)ethyl]amine, BArF4=B(3,5-(CF3)2C6H3)4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60° C., 1-4 atm H2). Nickel complex [(PNHPCy)Ni(H)]BPh4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNPCy)Ni(H) was used for hydrogenating alkenes.
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Paragraph 0036; 0054
(2015/12/07)
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- 2-indanole manufacturing method (by machine translation)
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PROBLEM TO BE SOLVED: To provide a method for producing 2-indanol which is useful as an intermediate for a pharmaceutical, a pesticide or the like, at high yield with high purity by using 2-indanone as a raw material compound.SOLUTION: A 2-indanone solution using alcohol as a solvent and adjusted so as to have pH of 4-7 by containing an organic acid is catalytically reduced with hydrogen in the presence of a nickel catalyst, to thereby produce 2-indanol. The alcohol is a 1-4C lower alcohol, and the organic acid is one kind or more selected from acetic acid and propionic acid. Though a method disclosed in a prior-art literature in which lithium aluminum hydride or sodium borohydride is used as a reducing agent is not an industrial processing, this method is an industrial processing because a high-yield high-purity production method is provided.
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Paragraph 0028-0044
(2019/08/21)
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- Highly efficient homogeneous and heterogenized ruthenium catalysts for transfer hydrogenation of carbonyl compounds
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[Ru(acac)2(CH3CN)2] was synthesized from [Ru(acac)3] by refluxing it with zinc powder in ethanol-acetonitrile mixture. The prepared catalyst was characterized by FT-IR, 1H and 13C NMR techniques. The silica supported catalyst ('SiO 2'-NH2-RuII) was prepared by stirring [Ru(acac)2(CH3CN)2] with 'SiO 2'-NH2 in a 1:1 mixture of CH2Cl 2-toluene for 3 days at room temperature. It was characterized by FT-IR, SEM, solid state NMR, ICP and BET surface area methods. The transfer hydrogenation reaction of carbonyl compounds was carried out separately using [Ru(acac)2(CH3CN)2] and 'SiO 2'-NH2-RuII as catalysts. The reaction conditions were optimized with different solvents, bases, catalyst amounts and temperatures using acetophenone as a model system. The scope of the reaction was extended to various substituted aryl ketones including heteroaryl ketones. This journal is the Partner Organisations 2014.
- Ganesamoorthy,Jerome,Shanmugasundaram,Karvembu
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p. 27955 - 27962
(2014/07/21)
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- Cobalt-catalyzed transfer hydrogenation of C=O and C=N bonds
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An earth-abundant metal cobalt catalyst has been developed for the transfer hydrogenation of ketones, aldehydes, and imines under mild conditions. Experiments are described which provide insights into the mechanism of the transfer hydrogenation reaction. The Royal Society of Chemistry 2013.
- Zhang, Guoqi,Hanson, Susan K.
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supporting information
p. 10151 - 10153
(2013/10/22)
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- Synthesis, pH-dependent, and plasma stability of meropenem prodrugs for potential use against drug-resistant tuberculosis
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Meropenem, a broad-spectrum parenteral β-lactam antibiotic, in combination with clavulanate has recently shown efficacy in patients with extensively drug-resistant tuberculosis. As a result of meropenem's short half-life and lack of oral bioavailability, the development of an oral therapy is warranted for TB treatment in underserved countries where chronic parenteral therapy is impractical. To improve the oral absorption of meropenem, several alkyloxycarbonyloxyalkyl ester prodrugs with increased lipophilicity were synthesized and their stability in physiological aqueous solutions and guinea pig as well as human plasma was evaluated. The stability of prodrugs in aqueous solution at pH 6.0 and 7.4 was significantly dependent on the ester promoiety with the major degradation product identified as the parent compound meropenem. However, in simulated gastrointestinal fluid (pH 1.2) the major degradation product identified was ring-opened meropenem with the promoiety still intact, suggesting the gastrointestinal environment may reduce the absorption of meropenem prodrugs in vivo unless administered as an enteric-coated formulation. Additionally, the stability of the most aqueous stable prodrugs in guinea pig or human plasma was short, implying a rapid release of parent meropenem.
- Teitelbaum, Aaron M.,Meissner, Anja,Harding, Ryan A.,Wong, Christopher A.,Aldrich, Courtney C.,Remmel, Rory P.
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p. 5605 - 5617
(2013/09/02)
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- Mild and homogeneous cobalt-catalyzed hydrogenation of C=C, C=O, and C=N bonds
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A cationic cobalt(II)-alkyl complex is an effective precatalyst for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (1-4 atm H2; see scheme). The catalyst shows a high functional-group tolerance across a broad range of substrates. Experiments suggest that the active catalytic species is a cobalt(II)-hydride complex. Copyright
- Zhang, Guoqi,Scott, Brian L.,Hanson, Susan K.
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supporting information
p. 12102 - 12106
(2013/01/16)
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- Magnesium-catalysed hydroboration of aldehydes and ketones
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The heteroleptic magnesium alkyl complex [CH{C(Me)NAr}2Mg nBu] (Ar = 2,6-iPr2C6H3) is reported as a highly efficient pre-catalyst for the hydroboration of aldehydes and ketones with pinacolborane. The Royal Society of Chemistry 2012.
- Arrowsmith, Merle,Hadlington, Terrance J.,Hill, Michael S.,Kociok-Koehn, Gabriele
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p. 4567 - 4569
(2012/06/05)
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- Cleavage of benzyl ethers by triphenylphosphine hydrobromide
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Triphenylphosphine hydrobromide was found to cleave the benzyl ethers derived from 1°, 2° alkyl, and aryl alcohols to the corresponding alcohols and benzyltriphenylphosphonium bromide in good yields. Alkene and allyl phosphonium salts were produced from the benzyl ethers with 3° alkyl and allyl groups, respectively. These results indicate that the formation of the product is determined by the relative stability of the carbocationic intermediate. The anhydrous, stoichiometric amount of PPh3·HBr offers a new and effective method for the deprotection of benzyl ethers.
- Ramanathan, Mani,Hou, Duen-Ren
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experimental part
p. 6143 - 6145
(2010/12/24)
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- Rhodium-catalysed hydroboration employing new Quinazolinap ligands; An investigation into electronic effects
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As part of an ongoing effort to improve the efficiency and substrate scope of our Quinazolinap ligand series in the rhodium-catalysed asymmetric hydroboration of vinyl arenes, 2-(p-trifluoromethylphenyl)-Quinazolinap and 2-(p-methoxyphenyl)-Quinazolinap have been synthesised and resolved in good yield. These, along with the previously reported 2-(2-pyridyl)-Quinazolinap and 2-(2-pyrazinyl)-Quinazolinap, form part of an electronic series of Quinazolinap ligands synthesised in order to explore electronic effects in this ligand class. The application of this series of ligands to the rhodium-catalysed asymmetric hydroboration of a range of vinylarenes is described. Good conversions and regioselectivities as well as excellent enantioselectivities up to 97% were obtained. 2-(p-Methoxyphenyl)-Quinazolinap demonstrated consistently high enantioselectivities in the hydroboration of sterically demanding vinylarenes.
- Maxwell, Aoife C.,Flanagan, Susan P.,Goddard, Richard,Guiry, Patrick J.
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experimental part
p. 1458 - 1473
(2010/11/03)
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- Gold-catalyzed oxidative coupling reactions with aryltrimethylsilanes
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During continuing studies with a novel oxidative gold oxyarylation reaction, arylsilanes were found to be competent coupling partners, providing further evidence for an intramolecular electrophilic aromatic substitution mechanism. While providing yields complementary to those of the previously described boronic acid methods, the use of trimethylsilanes reduces the observation of homocoupling byproducts and allows for facile intramolecular coupling reactions.
- Brenzovich Jr., William E.,Brazeau, Jean-Francois,Toste, F. Dean
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supporting information; scheme or table
p. 4728 - 4731
(2010/12/25)
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- Synthesis of phosphonate derivatives of 2,3-dihydroindene
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Simple and convenient procedures for the synthesis of derivatives of 2,3-dihydroinden-2-ylphosphonic acid are developed. The reaction strategies utilize both functionalization of the already existing 2,3-dihydroindene skeleton and an annulation reaction starting from readily available o-disubstituted benzene derivatives.
- Prokopowicz, Monika,M?ynarz, Piotr,Kafarski, Pawe?
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experimental part
p. 7314 - 7317
(2010/02/28)
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- A novel, chemoselective and efficient microwave-assisted deprotection of silyl ethers with Selectfluor
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A novel microwave-assisted, chemoselective and efficient method for the cleavage of silyl ethers (aliphatic and aromatic) catalyzed by Selectfluor is reported. A wide range of TBS-, TIPS-, and TBDPS-protected alkyl silyl ethers can be chemoselectively cleaved in high yield in the presence of aryl silyl ethers. The chemoselective deprotection of phenolic TBS ethers, and not the TIPS- or TBDPS-protected phenolic ethers, and the deprotection of silyl esters were also achieved under these reaction conditions. In addition, the transetherification and etherification of benzylic hydroxy groups in alcoholic solvents is observed.
- Shah, Syed Tasadaque A.,Singh, Surendra,Guiry, Patrick J.
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experimental part
p. 2179 - 2182
(2009/07/01)
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- The chemoselective and efficient deprotection of silyl ethers using trimethylsilyl bromide
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An efficient and chemoselective cleavage of silyl ethers (primary, secondary and aromatic) by using catalytic quantities of trimethylsilyl bromide (TMSBr) in methanol is reported. A wide range of alkyl silyl ethers such as TBS, TIPS, and TBDPS can be chemoselectively cleaved in high yield in the presence of aryl silyl ethers. The deprotection of silyl esters was also achieved employing catalytic quantities of TMSBr. The Royal Society of Chemistry 2008.
- Shah, Syed Tasadaque A.,Guiry, Patrick J.
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experimental part
p. 2168 - 2172
(2009/02/01)
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- The active role of NHC ligands in platinum-mediated tandem hydroboration-cross coupling reactions
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Stable N-heterocyclic platinum-carbene complexes are the first example of platinum-mediated regioselective H-B addition to vinylarenes and alkynes, allowing consecutive cross coupling reactions with the same catalytic system. The Royal Society of Chemistry.
- Lillo, Vanesa,Mata, Jose A.,Segarra, Anna M.,Peris, Eduardo,Fernandez, Elena
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p. 2184 - 2186
(2008/02/08)
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- Redox-photosensitized reaction of indene using photosensitive surfactant in emulsion: dependence on oil droplet size and surfactant charge
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A redox-photosensitized reaction of indene 2 using a photosensitive surfactant 1a in an oil-in-water emulsion proceeded efficiently to give alcohol 3 as a major product and is strongly influenced by the oil droplet size and surfactant charge.
- Yoshimi, Yasuharu,Itou, Tatsuya,Hatanaka, Minoru
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p. 3257 - 3260
(2007/10/03)
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- [CpRu(IV)(π-C3H5)(2-quinolinecarboxylato)]PF 6 complex: A robust catalyst for the cleavage and formation of allyl ethers
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A facile and efficient method for the quantitative synthesis of [CpRu(IV)(π-C3H5)(2-quinolinecarboxylato)]PF 6 from [CpRu(CH3CN)3]PF6, 2-quinolinecarboxylic acid, and 2-propen-1-ol has been established. The cationic Ru(IV) complex is air- and moisture-stable, and can be stored in a vial for at least six months. This complex realizes a simple and easy operation for both the deallylation of allyl ethers in methanol and the dehydrative allylation of alcohols. Furthermore, with removal of the volatile allyl methyl ether co-product from the reaction system, the robust catalyst can attain a turnover of 10000 cycles of allyl ether cleavage.
- Tanaka, Shinji,Saburi, Hajime,Kitamura, Masato
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p. 375 - 378
(2007/10/03)
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- Solvent-free reduction of aldehydes and ketones using solid acid-activated sodium borohydride
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A simple and convenient procedure for the reduction of aldehydes and ketones with sodium borohydride activated by solid acids such as boric acid, benzoic acid, and p-toluenesulfonic acid monohydrate under solvent-free conditions is described.
- Cho, Byung Tae,Kang, Sang Kyu,Kim, Min Sung,Ryu, Soo Ryeon,An, Duk Keun
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p. 8164 - 8168
(2007/10/03)
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- Radical hydrogen abstraction-cyclization with a 2-bromovinylsilyl group as a bifunctional tether
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In order to develop an efficient method for the regio- and stereoselective introduction of a carbon substituent, a radical hydrogen abstraction-cyclization using 1- and 2-bromovinylsilyl groups as bifunctional tethers was studied. Although, the selective introduction of a carbon substituent at the position β to the hydroxyl was unsuccessful, a carbon substituent was introduced with the 2-bromovinylsilyl ethers via a hydrogen abstraction-cyclization. These reactions were analyzed based on the bond dissociation energies obtained by theoretical calculations.
- Sukeda, Makoto,Matsuda, Akira,Shuto, Satoshi
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p. 7865 - 7873
(2007/10/03)
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- Method of removing allyl series protecting group using novel ruthenium complex and method of synthesizing allyl ethers
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A cyclopentadienyl ruthenium (II) complex or (iv) complex having an α-imino acid type ligand or an α-amino acid type ligand.
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Page/Page column 4
(2010/02/14)
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- Alkene-pinacolborane hydroborations catalyzed by lanthanum tris[bis(trimethylsilyl)amide]
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Tris[bis(trimethylsilyl)amide] has been shown to be an effective catalyst for the hydroboration of representative alkenes and styrenes by pinacolborane.
- Horino, Yoshikazu,Livinghouse, Tom,Stan, Magdalena
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p. 2639 - 2641
(2007/10/03)
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- Dichloromethane activation. Direct methylenation of ketones and aldehydes with CH2Cl2 promoted by Mg/TiCl4/THF
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(Chemical Equation Presented) This Mg-TiCl4-promoted CH 2-transfer reaction of CH2Cl2 represents an extremely simple, practical, and efficient methylenation of a variety of ketones and aldehydes, especially in enolizable or sterically hindered ketones such as 2,2-dimethylcyclohexanone, camphor, and fenchone.
- Yan, Tu-Hsin,Tsai, Chia-Chung,Chien, Ching-Ting,Cho, Chia-Ching,Huang, Pei-Chen
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p. 4961 - 4963
(2007/10/03)
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- Preparation and resolution of a modular class of axially chiral quinazoline-containing ligands and their application in asymmetric rhodium-catalyzed olefin hydroboration
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The preparation and resolution of a series of axially chiral quinazoline-containing ligands is described in which the key steps are the metal-catalyzed naphthyl-phosphorus bond formation, the naphthalene-quinazoline Suzuki coupling, and the preparation of the Suzuki electrophilic components from the corresponding imidate and anthranilic acid. Diastereomeric palladacycles derived from the racemic phosphinamines and (+)-di-μ-chlorobis[(R)- dimethyl(1-(1-naphthyl)ethyl)-aminato-C2,N]dipalladium(II) were separated by fractional crystallization. The configuration of the resulting diastereomers was determined by X-ray crystallographic analysis. Displacement of the resolving agent by reaction with 1,2-bis(diphenylphosphino)ethane afforded enantiopure ligand in each case. Their rhodium complexes were prepared and applied in the enantioselective hydroboration of a range of vinylarenes. The quinazolinap catalysts were found to be extremely active, giving excellent conversions, good to complete regioselectivities, and the highest enantioselectivities obtained to date for several members of the vinylarene class, including cis-β-methylstyrene (97%), cis-stilbene (99%), and indene (99.5%).
- Connolly, David J.,Lacey, Patrick M.,McCarthy, Mary,Saunders, Cormac P.,Carroll, Anne-Marie,Goddard, Richard,Guiry, Patrick J.
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p. 6572 - 6589
(2007/10/03)
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- First Carbamates Conversion to Amides by Simple Alkyl Group Transfer from Trialkylalanes
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(Equation presented) N-Monosubstituted carbamates are cleanly converted to amides under treatment with trialkylaluminum. This reaction involves an aluminum-assisted internal delivery of alkyl groups. It can be applied to new and mild protecting group strategies for alcohols.
- El Kaim, Laurent,Grimaud, Laurence,Lee, Anabelle,Perroux, Yannick,Tirla, Cornelia
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p. 381 - 383
(2007/10/03)
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- CpRuIIPF6/quinaldic acid-catalyzed chemoselective allyl ether cleavage. A simple and practical method for hydroxyl deprotection
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Matrix presented. A cationic CpRuII complex in combination with quinaldic acid shows high reactivity and chemoselectivity for the catalytic deprotection of hydroxyl groups protected as allyl ethers. The catalyst operates in alcoholic solvents without the need for any additional nucleophiles, satisfying the practical requirements of operational simplicity, safety, and environmental friendliness. The wide applicability of this deprotection strategy to a variety of multifunctional molecules, including peptides and nucleosides, may provide new opportunities in protective group chemistry.
- Tanaka, Shinji,Saburi, Hajime,Ishibashi, Yoshitaka,Kitamura, Masato
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p. 1873 - 1875
(2007/10/03)
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- ZnI2/NaCNBH3 as an Efficient Reagent for Regioselective Ring Opening of the Benzylic Epoxide Moiety
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In the presence of zinc iodide, sodium cyanoborohydride was found to produce regioselective ring opening of benzylic epoxides in mild reaction conditions.
- Finkielsztein,Aguirre,Lantano,Alesso,Moltrasio Iglesias
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p. 895 - 901
(2007/10/03)
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- Indium-mediated reductive elimination of halohydrins
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Olefin formation has been successfully carried out by reductive elimination reactions of halohydrins with Pd(PPh3)4/In/InCl3 in aqueous media.
- Cho, Sangwon,Kang, Soyeon,Keum, Gyochang,Kang, Soon Bang,Han, So-Yeop,Kim, Youseung
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p. 180 - 182
(2007/10/03)
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- Olefin isomerization by a ruthenium carbenoid complex. Cleavage of allyl and homoallyl groups
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Ruthenium-carbenoid catalysts such as Grubbs' complex I mediate efficiently the isomerization of β,γ-unsaturated ethers and amines to the corresponding vinyl ethers and enamines. This reaction can be useful in the deprotection of allyl and homoallyl ethers as well as amines.
- Cadot, Christine,Dalko, Peter I,Cossy, Janine
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p. 1839 - 1841
(2007/10/03)
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- Reduction of aliphatic and aromatic cyclic ketones to sec-alcohols by aqueous titanium trichloride/ammonia system. Steric course and mechanistic implications
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In contrast to the dissolved metal and metal hydride reductions, the reduction of cyclic ketones by the aqueous TiCl3/NH3 system favours the formation of the less thermodynamically stable axial alcohol. The ammonium ion formed in situ is essential for the reduction to proceed because it behaves as a mild Br?nsted acid in basic medium and favours the protonation of the intermediate ketyl. The corresponding α-hydroxy radical is then rapidly reduced under conditions where the first electron transfer to the substrate takes place. We suggest that the stereoselectivity is determined by the second reduction step, which occurs through the less hindered transition state, regardless of whether the radical to be reduced is thermodynamically favoured or not.
- Clerici, Angelo,Pastori, Nadia,Porta, Ombretta
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p. 2235 - 2243
(2007/10/03)
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- Stereoselective benzylic hydroxylation of 2-substituted indanes using toluene dioxygenase as biocatalyst
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Indane, 1A, and a series of 2-substituted indane substrates, 1B-1D, 1G, 1I-1L, were found to undergo benzylic monohydroxylation catalysed by toluene dioxygenase, present in the intact cells of Pseudomonas putida UV 4, to yield enantiopure cis-indan-1-ols, 2A-2D, 2G, 2I-2L of the same absolute configuration at C-1 as major bioproducts. Enantiopure trans-indan-1-ols 6B, 6C, and 6G were also obtained as minor metabolites. Evidence of further sequential benzylic hydroxylation (bis-hydroxylation) was found only with substrates 2A, 1C, 1D and 1L to yield the corresponding enantiopure trans-1,3-diols, 3A, 3C, 3D and 3L. Minor enzyme-catalysed processes also observed include benzylic alcohol oxidation to ketones (4A, 5A, 4B, 4L, 5L), ketone reduction to benzylic alcohol 6A, ester hydrolysis to indan-2-ol 1B, and cis-dihydroxylation of indan-1-ol 6A to triol 7. The enantiopurities and absolute configurations of bioproducts have been determined using MTPA ester formation, circular dichroism spectroscopy and stereochemical correlation methods. The contribution of asymmetric oxidation and kinetic resolution to the production of bioproducts of high ee (>98%), and the metabolic sequence involved in their biotransformation by P. putida UV4 is discussed. Enantiocomplementarity was found during the benzylic hydroxylation of indan-2-ol 1B, using toluene dioxygenase and naphthalene dioxygenase, when both single enantiomers of the metabolites 2B, 4B and 6B of opposite configurations were obtained.
- Bowers, Nigel I.,Boyd, Derek R.,Sharma, Narain D.,Goodrich, Peter A.,Groocock, Melanie R.,Blacker, A. John,Goode, Paul,Dalton, Howard
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p. 1453 - 1461
(2007/10/03)
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- Scandium trifluoromethanesulfonate-catalyzed cleavage of esters bearing a coordinative group at a vicinal position
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Scandium trifluoromethanesulfonate is found to be a Lewis acid catalyst for selective cleavage of esters containing a coordinative group adjacent to an ester moiety. The reaction proceeds under weak acidic conditions at room temperature; the catalyst can be recovered and reused. Even α-acyloxy ketones are deacetylated without racemization. Selective monodeacetylation at C-10 of paclitaxel has been achieved.
- Kajiro, Hiroshi,Mitamura, Shuichi,Mori, Atsunori,Hiyama, Tamejiro
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p. 1553 - 1560
(2007/10/03)
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- Biocatalysis of Deracemization in 1,2-Diols
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The fungus Corynosporium cassicola DSM 62475 is shown to induce deracemization in certain 1,2-diols, including the synthetically important indane-1,2-diol, by enantioconvergent stereoinversion processes in which the recovered enantiomer is not a substrate for the dehydrogenase enzymes involved.
- Page, Philip C. Bulman,Carnell, Andrew J.,McKenzie, Michael J.
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p. 774 - 776
(2007/10/03)
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- Trimethylsilyl chloride-accelerated reduction and pinacol coupling of carbonyl compounds by means of samarium diiodide
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The combination of samarium diiodide (SmI2) and trimethylsilyl chloride (Me3SiCl) in THF-HMPA is found to accelerate the reduction of sterically hindered and enolisable ketones, and also to accelerate pinacolisation of the carbonyl compounds depending on the reaction conditions.
- Honda, Toshio,Katoh, Miho
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p. 369 - 370
(2007/10/03)
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- Pd-catalysed regiospecific reductive ring opening of epoxides and glycidic esters
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The regiospecific ring opening of epoxides was achieved by Pd-catalysed transfer hydrogenolysis using ammonium formate as hydrogen source.
- Varghese,Sudalai,Iyer
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p. 2267 - 2273
(2007/10/02)
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- Silica Gel Supported Zinc Borohydride. A Novel Reagent for Hydration of Unactivated Alkenes and Alkynes
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A simple and general procedure for hydration of unactivated alkenes and alkynes producing less substituted alcohols selectively has been achieved by the reaction of the corresponding alkenes or alkynes on silica gel support with zinc borohydride in 1,2-dimethoxyethane.
- Ranu, Brindaban C.,Sarkar, Arunkanti,Saha, Manika,Chakraborty, Rupak
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p. 6579 - 6584
(2007/10/02)
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