- Zinc salt-catalyzed reduction of α-aryl imino esters, diketones and phenylacetylenes with water as hydrogen source
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The zinc salt-catalyzed reduction of α-aryl imino esters, diketones and phenylacetylenes with water as hydrogen source and zinc as reductant was successfully conducted. The presented method provides a low-cost, environmentally friendly and practical preparation of α-aryl amino esters, α-hydroxyketones and phenylethylenes. By using D2O as deuterium source, the corresponding products were obtained in high efficiency with excellent deuterium incorporation rate, which gives a cheap and safe tool for access to valuable deuterium-labelled compounds. This journal is
- Shen, Guoli,Liu, Haojie,Chen, Jingchao,He, Zhenxiu,Zhou, Yongyun,Wang, Lin,Luo, Yang,Su, Zhimin,Fan, Baomin
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supporting information
p. 3601 - 3610
(2021/05/04)
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- g-C3N4/metal halide perovskite composites as photocatalysts for singlet oxygen generation processes for the preparation of various oxidized synthons
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g-C3N4/metal halide perovskite composites were prepared and used for the first time as photocatalysts forin situ1O2generation to perform hetero Diels-Alder, ene and oxidation reactions with suitable dienes and alkenes. The standardized methodology was made applicable to a variety of olefinic substrates. The scope of the method is finely illustrated and the reactions afforded desymmetrized hydroxy-ketone derivatives, unsaturated ketones and epoxides. Some limitations were also observed, especially in the case of the alkene oxidations, and poor chemoselectivity was somewhere observed in this work which is the first application of MHP-based composites forin situ1O2generation. The experimental protocol can be used as a platform to further expand the knowledge and applicability of MHPs to organic reactions, since perovskites offer a rich variety of tuning strategies which may be explored to improve reaction yields and selectivities.
- Corti, Marco,Chiara, Rossella,Romani, Lidia,Mannucci, Barbara,Malavasi, Lorenzo,Quadrelli, Paolo
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p. 2292 - 2298
(2021/04/12)
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- Whole-Cell Biocatalysis in Seawater: New Halotolerant Yeast Strains for the Regio- and Stereoselectivity Reduction of 1-Phenylpropane-1,2-Dione in Saline-Rich Media
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The application of green chemistry concepts in catalysis has considerably increased in recent years, and the interest in using sustainable solvents in the chemical industry is growing. One of the recent proposals to fall in line with this is to employ seawater as a solvent in biocatalytic processes. This involves selecting halotolerant strains capable of carrying out chemical conversions in the presence of the salt concentrations found in this solution. Recent studies by our group have revealed the interest in using strains belonging to Debaryomyces and Schwanniomyces for catalytic processes run in this medium. In the present work, we select other yeasts based on their halotolerance to widen the scope of this strategy. We consider them for the monoreduction of 1-phenylpropane-1,2-dione, a well-characterized reaction that produces acyloin intermediates of pharmaceutical interest. The results obtained herein indicate that using seawater as a solvent for this reaction is possible. The best ones were obtained for Saccharomyces cerevisiae FY86 and Kluyveromyces marxianus, for which acyloins with different stereochemistry were obtained with good to excellent enantiomeric excess.
- Andreu, Cecilia,del Olmo, Marcellí
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p. 1621 - 1628
(2020/03/05)
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- Iron-catalyzed regiodivergent alkyne hydrosilylation
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Although tremendous effort has been devoted to the development of methods for iron catalysis, few of the catalysts reported to date exhibit clear superiority to other metal catalysts, and the mechanisms of most iron catalysis remain unclear. Herein, we report that iron complexes bearing 2,9-diaryl-1,10-phenanthroline ligands exhibit not only unprecedented catalytic activity but also unusual ligand-controlled divergent regioselectivity in hydrosilylation reactions of various alkynes. The hydrosilylation protocol described herein provides a highly efficient method for preparing useful di- and trisubstituted olefins on a relatively large scale under mild conditions, and its use markedly improved the synthetic efficiency of a number of bioactive compounds. Mechanistic studies based on control experiments and density functional theory calculations were performed to understand the catalytic pathway and the observed regioselectivity.
- Hu, Meng-Yang,He, Peng,Qiao, Tian-Zhang,Sun, Wei,Li, Wen-Tao,Lian, Jie,Li, Jin-Hong,Zhu, Shou-Fei
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p. 16894 - 16902
(2020/10/09)
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- Regio- and stereoselective multi-enzymatic aminohydroxylation of β-methylstyrene using dioxygen, ammonia and formate
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We report an enzymatic route for the formal regio- and stereoselective aminohydroxylation of β-methylstyrene that consumes only dioxygen, ammonia and formate; carbonate is the by-product. The biocascade entails highly selective epoxidation, hydrolysis and hydrogen-borrowing alcohol amination. Thus, β-methylstyrene was converted into 1R,2R and 1S,2R-phenylpropanolamine in 59-63% isolated yields, and up to >99.5 : 0.5 dr and er.
- Corrado, Maria L.,Knaus, Tanja,Mutti, Francesco G.
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supporting information
p. 6246 - 6251
(2019/12/03)
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- Sequential Reduction of Nitroalkanes Mediated by CS2 and Amidine/Guanidine Bases: A Controllable Nef Reaction
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In this letter, we describe a mild, functional group-tolerant reductive Nef reaction that utilizes CS2 and an amidine or guanidine base to sequentially cleave N-O bonds. These conditions transform secondary nitroalkanes to ketones via an isolable oxime with minimal erosion at labile stereogenic carbons, show excellent compatibility with groups sensitive to oxidizing or reducing conditions, display good scalability, and are well-suited for generating useful 3-pyrrolidinone motifs from readily accessible 1,3-dipolar cycloaddition products.
- Ju, Minsoo,Guan, Weiyang,Schomaker, Jennifer M.,Harper, Kaid C.
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p. 8893 - 8898
(2019/11/11)
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- Homogeneous Palladium-Catalyzed Transfer Hydrogenolysis of Benzylic Alcohols Using Formic Acid as Reductant
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We report the first homogeneous palladium-based transfer hydrogenolysis of benzylic alcohols using an in situ formed palladium-phosphine complex and formic acid as reducing agent. The reaction requires a catalyst loading as low as only 1 mol % of palladium and just a slight excess of reductant to obtain the deoxygenated alkylarenes in good to excellent yields. Besides demonstrating the broad applicability for primary, secondary and tertiary benzylic alcohols, a reaction intermediate could be identified. Additionally, it could be shown that partial oxidation of the applied phosphine ligand was beneficial for the course of the reaction, presumably by stabilizing the active catalyst. Reaction profiles and catalyst poisoning experiments were used to characterize the catalyst, the results of which indicate a homogeneous metal complex as the active species.
- Ciszek, Benjamin,Fleischer, Ivana
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supporting information
p. 12259 - 12263
(2018/08/28)
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- Purified mCPBA, a Useful Reagent for the Oxidation of Aldehydes
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Purified mCPBA is a useful reagent for the oxidation of several classes of aldehyde. Although linear unbranched aliphatic aldehydes are oxidized to the corresponding carboxylic acids, α-branched ones undergo Baeyer–Villiger oxidation to formates. α-Branched α,β-unsaturated aldehydes provide enolformates and/or epoxides, which can be saponified to α-hydroxy ketones with shortening of the carbon chain by 1 carbon. Unbranched α,β-unsaturated aldehydes undergo an interesting Baeyer–Villiger oxidation/epoxidation/formate migration/BV oxidation cascade, which results in formyl-protected hydrates with an overall loss of two carbon atoms.
- Horn, Alexander,Kazmaier, Uli
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supporting information
p. 2531 - 2536
(2018/03/21)
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- Organocatalytic Enantioselective Protonation for Photoreduction of Activated Ketones and Ketimines Induced by Visible Light
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The first catalytic asymmetric photoreduction of 1,2-diketones and α-keto ketimines under visible light irradiation is reported. A transition-metal-free synergistic catalysis platform harnessing dicyanopyrazine-derived chromophore (DPZ) as the photoredox catalyst and a non-covalent chiral organocatalyst is effective for these transformations. With the flexible use of a chiral Br?nsted acid or base in H+ transfer interchange to control the elusive enantioselective protonation, a variety of chiral α-hydroxy ketones and α-amino ketones were obtained with high yields and enantioselectivities.
- Lin, Lu,Bai, Xiangbin,Ye, Xinyi,Zhao, Xiaowei,Tan, Choon-Hong,Jiang, Zhiyong
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supporting information
p. 13842 - 13846
(2017/10/24)
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- Internal Alkyne Regio- and Chemoselectivity using a Zwitterionic N-Heterocyclic Carbene Gold Catalyst in a Silver-Free Alkyne Hydration Reaction
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An alkyne hydration of terminal and internal alkynes is reported using a zwitterionic N-heterocyclic carbene gold catalyst [(BNHC)Au(SMe2)] in the absence of silver and Br?nsted acid additives. The hydration demonstrates good regioselectivity in alkyne hydration and chemoselectivity for internal alkynes vs. terminal. In addition, (BNHC)Au(SMe2) performs a propargyl alcohol hydration to predominantly form α-hydroxymethyl ketone over the more common Meyer–Schuster rearrangement product. While complex (BNHC)Au(SMe2) is active without silver additives, addition of silver hexafluoroantimonate (AgSbF6) increases reaction rate and decreases selectivity for internal alkyne hydration over terminal substrates. To the best of our knowledge, the rate enhancement of (BNHC)Au(SMe2) by AgSbF6is the first such demonstration of a silver effect for a “halide-free” Au catalyst. (Figure presented.).
- Weerasiri, Kushan C.,Chen, Danmin,Wozniak, Derek I.,Dobereiner, Graham E.
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p. 4106 - 4113
(2016/12/30)
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- Chemoselective N-heterocyclic carbene-catalyzed cross-benzoin reactions: Importance of the fused ring in triazolium salts
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Morpholinone- and piperidinone-derived triazolium salts are shown to catalyze highly chemoselective cross-benzoin reactions between aliphatic and aromatic aldehydes. The reaction scope includes ortho-, meta-, and para-substituted benzaldehyde derivatives with a range of electron-donating and -withdrawing groups as well as branched and unbranched aliphatic aldehydes. Catalytic loadings as low as 5 mol % give excellent yields in these reactions (up to 99%).
- Langdon, Steven M.,Wilde, Myron M.D.,Thai, Karen,Gravel, Michel
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supporting information
p. 7539 - 7542
(2014/06/10)
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- Boronic acid-catalyzed selective oxidation of 1,2-diols to α-hydroxy ketones in water
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The activation of 1,2-diols through formation of boronate esters was found to enhance the selective oxidation of 1,2-diols to their corresponding α-hydroxy ketones in aqueous medium. The oxidation step was accomplished using dibromoisocyanuric acid (DBI) as a terminal chemical oxidant or an electrochemical process. The electrochemical process was based on the use of platinum electrodes, methylboronic acid [MeB(OH)2] as a catalyst and bromide ion as a mediator. Electro-generated OH- ions (EGB) at the cathode acted as a base and "Br+" ion generated at the anode acted as an oxidant. Various cyclic and acyclic 1,2-diols as substrates were selectively oxidized to the corresponding α-hydroxy ketones via their boronate esters by the two oxidative methods in good to excellent yields.
- William, Julius M.,Kuriyama, Masami,Onomura, Osamu
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supporting information
p. 934 - 940
(2014/04/03)
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- Copper-catalyzed benzylic oxidation of C(sp3)-H bonds
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A selective oxidation of benzylic C(sp3)-H bonds to C(sp 3)-O bonds catalyzed by copper complexes of quinoline-imine ligands was developed with peresters as oxidants under mild reaction conditions, which converted benzylic methylenes directly into benzylic alcohols and esters by means of direct C-H bond functionalization.
- Zhang, Bo,Zhu, Shou-Fei,Zhou, Qi-Lin
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supporting information
p. 2033 - 2037
(2013/03/13)
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- Measurement of stable isotope ratios in methylamphetamine: A link to its precursor source
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The illicit drug methylamphetamine is often prepared from the precursor ephedrine or pseudoephedrine, which in turn are obtained by three processes: extraction from the Ephedra plant ("natural"), via fermentation of sugars ("semi-synthetic"), and by a "fully synthetic" route from propiophenone. We report the first method to differentiate between the three industrial routes used to produce the precursors ephedrine and pseudoephedrine by measurement of stable isotope ratios of nitrogen (δ15N), hydrogen (δ2H), and carbon (δ13C). Analysis of 782 samples of seized methylamphetamine allowed classification into three groups using k-means clustering or the expectation-maximization algorithm applied to a Gaussian mixture model. By preparation of 30 samples of ephedrine by the "fully synthetic" industrial process and measuring their δ15N, δ2H, and δ13C values, we observed that 15N becomes significantly depleted compared to the methylamine starting material. Conversion of ten ephedrine samples to methylamphetamine showed that this depletion is maintained in the final drug product, of which the δ15N, δ13C, and δ2H values were distinct from those of ephedrine and methylamphetamine samples of a semi-synthetic (fermentation pathway) origin. Combining modeling analysis with the new experiments and published information on the values of δ2H gave a definitive assignment of the three model groups, and equations to obtain probabilities for the precursor origin of any new sample. A simple rule of thumb is also presented. Making an assignment using delta values is particularly useful when no other chemical profiling information is available.
- Salouros, Helen,Sutton, Gordon J.,Howes, Joanna,Hibbert, D. Brynn,Collins, Michael
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p. 9400 - 9408
(2013/10/21)
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- Stereoselective synthesis of norephedrine and norpseudoephedrine by using asymmetric transfer hydrogenation accompanied by dynamic kinetic resolution
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Each of the enantiomers of both norephedrine and norpseudoephedrine were stereoselectively prepared from the common, prochiral cyclic sulfamidate imine of racemic 1-hydroxy-1-phenyl-propan-2-one by employing asymmetric transfer hydrogenation (ATH) catalyzed by the well-defined chiral Rh-complexes, (S,S)- or (R,R)-Cp*RhCl(TsDPEN), and HCO2H/Et3N as the hydrogen source. The ATH processes are carried out under mild conditions (rt, 15 min) and are accompanied by dynamic kinetic resolution.
- Lee, Hyeon-Kyu,Kang, Soyeong,Choi, Eun Bok
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experimental part
p. 5454 - 5460
(2012/08/27)
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- α-Diketones as acyl anion equivalents: A non-enzymatic thiamine-promoted route to aldehyde-ketone coupling in PEG400 as recyclable medium
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By mimicking the peculiar behavior of thiamine diphosphate-dependent acetylacetoin synthase, it has been demonstrated that thiamine hydrochloride 2a and its simple analogue thiazolium salt 2b are able to activate α-diketones as acyl anion equivalents in nucleophilic acylations, such as the homo-coupling of α-diketones and the hitherto unreported cross-coupling between α-diketones and α-ketoesters. These carboligation reactions were optimized under stoichiometric (2a) and catalytic conditions (2b) by using eco-friendly PEG400 as the reaction medium, thus allowing both solvent and thiazolium salt recycling.
- Bortolini, Olga,Fantin, Giancarlo,Fogagnolo, Marco,Giovannini, Pier Paolo,Venturi, Valentina,Pacifico, Salvatore,Massi, Alessandro
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experimental part
p. 8110 - 8115
(2011/10/31)
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- Hyphenating the curtius rearrangement with morita-baylis-hillman adducts: Synthesis of biologically active acyloins and vicinal aminoalcohols
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Using Morita-Baylis-Hillman adducts as substrates, the Curtius rearrangement was performed in a sequence that allowed the synthesis of several hydroxy-ketones (acyloins) with great structural diversity and in good overall yields. These acyloins in turn were easily transformed into 1,2-anti aminoalcohols through a highly diastereoselective reductive amination step. The synthetic utility of these approaches was exemplified by performing the syntheses of (±)-bupropion, a drug used to treat the abstinence syndrome of smoker and (±)-spisulosine, a potent anti-tumoral compound originally isolated form a marine source.
- Amarante, Giovanni W.,Cavallaro, Mayra,Coelho, Fernando
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p. 1568 - 1584
(2011/11/06)
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- Switching regioselectivity in crossed acyloin condensations between aromatic aldehydes and acetaldehyde by altering n -heterocyclic carbene catalysts
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An unprecedented high level of regioselectivities (up to 96%) in the intermolecular crossed acyloin condensations of various aromatic aldehydes with acetaldehyde was realized by an appropriate choice of N-heterocyclic carbene catalysts.(Figure Presented)
- Jin, Ming Yu,Kim, Sun Min,Han, Hogyu,Ryu, Do Hyun,Yang, Jung Woon
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supporting information; experimental part
p. 880 - 883
(2011/05/02)
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- Cis-dihydroxylation of alkenes with oxone catalyzed by iron complexes of a macrocyclic tetraaza ligand and reaction mechanism by ESI-MS spectrometry and DFT calculations
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[FeIII(L-N4Me2)Cl2]+ (1, L-N4Me2 = N,N′-dimethyl-2,11-diaza[3.3](2,6) pyridinophane) is an active catalyst for cis-dihydroxylation of various types of alkenes with oxone at room temperature using limiting amounts of alkene substrates. In the presence of 0.7 or 3.5 mol % of 1, reactions of electron-rich alkenes, including cyclooctene, styrenes, and linear alkenes, with oxone (2 equiv) for 5 min resulted in up to >99% substrate conversion and afforded cis-diol products in up to 67% yield, with cis-diol/epoxide molar ratio of up to 16.8:1. For electron-deficient alkenes including α,β-unsaturated esters and α,β-unsaturated ketones, their reactions with oxone (2 equiv) catalyzed by 1 (3.5 mol %) for 5 min afforded cis-diols in up to 99% yield with up to >99% substrate conversion. A large-scale cis-dihydroxylation of methyl cinnamate (9.7 g) with oxone (1 equiv) afforded the cis-diol product (8.4 g) in 84% yield with 85% substrate conversion. After catalysis, the L-N4Me2 ligand released due to demetalation can be reused to react with newly added Fe(ClO4)2?4H2O to generate an iron catalyst in situ, which could be used to restart the catalytic alkene cis-dihydroxylation. Mechanistic studies by ESI-MS, isotope labeling studies, and DFT calculations on the 1-catalyzed cis-dihydroxylation of dimethyl fumarate with oxone reveal possible involvement of cis-HO-Fe V O and/or cis-O FeV O species in the reaction; the cis-dihydroxylation reactions involving cis-HO-FeV O and cis-O FeV O species both proceed by a concerted but highly asynchronous mechanism, with that involving cis-HO-FeV O being more favorable due to a smaller activation barrier.
- Chow, Toby Wai-Shan,Wong, Ella Lai-Ming,Guo, Zhen,Liu, Yungen,Huang, Jie-Sheng,Che, Chi-Ming
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experimental part
p. 13229 - 13239
(2010/12/19)
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- Formation of α-hydroxyketones via irregular Wittig reaction
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Αddition reactions of (1-methoxyalkyl)triphenylphosphonium ylides, derived from the corresponding Wittig salts and n-BuLi, to aldehydes were investigated. It was revealed that the betaine LiX complexes, the primary adducts, were converted to α-hydroxyketones, prior to the formation of oxaphosphetanes, by addition of aqueous NH4Cl at low temperature.
- Okada, Hideki,Mori, Tomonori,Saikawa, Yoko,Nakata, Masaya
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supporting information; experimental part
p. 1276 - 1278
(2009/09/05)
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- Enantioselective C - C bond ligation using recombinant Escherichia coli-whole-cell biocatalysts
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Thiamine diphosphate (ThDP)-dependent enzymes like benzaldehyde lyase from Pseudomonas fluorescens (BAL) and benzoylformate decarboxylase from Pseudomonas putida (BFD) are versatile biocatalysts for the C - C bond ligation of aldehydes to form enantiomerically pure 2-hydroxy ketones. However, the large-scale application of this enzyme class is often restricted by the required external addition of the expensive cofactor ThDP, as well as by the common use of dimethyl sulfoxide (DMSO) as a cosolvent, which leads to problems during the work-up procedure. In the present paper we demonstrate that the addition of the excess cofactors, ThDP and magnesium ions (Mg2+), is not required when BAL or BFD are used in Escherichia coli resting cells. Furthermore, the combination of these resting cells with a biphasic reaction medium [methyl tert-butyl ether (MTBE)/aqueous buffer] allows an increase of the substrate concentration up to 1M, and an efficient extractive work-up. As a practical example, e.g., the synthesis of (R)-2-hydroxy-3,3-dimethoxy-phenylpropanone from benzaldehyde and 2,2-dimethoxyacetaldehyde was optimized, achieving an isolated yield of 78 %, and an enantiomeric excess of 98% ee in 24 h when operating at a substrate concentration of 0.4 M. The described reaction system in a biphasic medium is suitable for a wide range of aldehydes as substrates. The biphasic reaction medium minimizes also the formation of by-products, which were observed when this reaction was performed in the conventional DMSO/buffer system.
- De Maria, Pablo Dominguez,Stillger, Thomas,Pohl, Martina,Kiesel, Michael,Liese, Andreas,Groeger, Harald,Trauthwein, Harald
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experimental part
p. 165 - 173
(2009/04/07)
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- A combined NMR, DFT, and X-ray investigation of some cinchona alkaloid O-ethers
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(Chemical Equation Presented) Structures and conformational behavior of several cinchona alkaloid O-ethers in the solid state (X-ray), in solution (NMR and DFT), and in the gas phase (DFT) were investigated. In the crystal, O-phenylcinchonidine adopts the Open(3) conformation similar to cinchonidine, whereas the O-methyl ether derivatives of both cinchonidine and cinchonine are packed in the Closed(1) conformation. Dynamic equilibria in solutions of the alkaloids were revealed by combined experimental-theoretical spin simulation/iteration techniques for the first time. In the 1H NMR spectra in CDCl3 and toluene-d8 at room temperature, Closed(1) conformation was observed for the O-silyl ethers as a separate set of signals. For O-methyl ether derivatives Closed(1) could be separated only at -30°C in CDCl3 or toluene-d8 and for O-phenylcinchonidine at -70°C in CDCl3/CD2Cl2. The ratio between the Closed(2) and Open(3) conformers was estimated by analyzing the vicinal coupling constant 3JH9,H8 at ambient and low temperatures. The observed conformational equilibria of O-(tert-butyldimethylsilyl) cinchonidine in CDCl3 and toluene-d8 are in good agreement with the theoretically estimated equilibrium populations of the conformations according to Boltzmann statistics. The conformational equilibria of four cinchona alkaloid O-ether solutes in CDCl3 and toluene-d8 are discussed in the light of their relevance to the mechanism of 1-phenyl-1,2-propanedione (PPD) hydrogenation over cinchona alkaloid modified heterogeneous platinum catalysts. It was demonstrated that the conformation found to be abundant in the liquid phase has no direct correlation with the enantioselectivity of the PPD hydrogenation reaction.
- Busygin, Igor,Nieminen, Ville,Taskinen, Antti,Sinkkonen, Jari,Toukoniitty, Esa,Sillanpaeae, Reijo,Murzin, Dmitry Yu.,Leino, Reko
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p. 6559 - 6569
(2008/12/22)
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- Reduction of activated carbonyl groups by alkyl phosphines: Formation of α-hydroxy esters and ketones
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Reduction of activated carbonyl groups such as α-keto esters, benzils, 1,2-cyclohexanedione, and α-ketophosphonates by alkyl phosphines afforded the corresponding α-hydroxy esters or ketones in good to excellent yields in THF at room temperature. The mechanism of the proton transfer and intramolecular hydrolysis has been studied on the basis of deuterium and 18O labeling experiments. The Royal Society of Chemistry 2006.
- Zhang, Wen,Shi, Min
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p. 1218 - 1220
(2008/02/03)
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- Highly chemoselective hydrogenation method using novel finely dispersed palladium catalyst on silk-fibroin: Its preparation and activity
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A palladium-fibroin complex (Pd/Fib) was prepared by soaking silk-fibroin in MeOH solution of Pd(OAc)2 for 2 days (under Ar atmosphere) - 4 days (under air). Pd(OAc)2 was gradually absorbed by fibroin and the rapid reduction of fibroin conjugated Pd(OAc)2 proceeded with MeOH as a reductant at room temperature to be the Pd(0) complex. Pd/Fib catalyzed chemoselective hydrogenation of acetylenes, olefins and azides in the presence of aromatic ketones and aldehydes, halides, N-Cbz protective groups and benzyl esters which are readily hydrogenated using Pd/C or Pd/C(en) as a catalyst.
- Ikawa, Takashi,Sajiki, Hironao,Hirota, Kosaku
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p. 2217 - 2231
(2007/10/03)
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- New oxidative transformations of alkenes and alkynes under the action of diacetoxyiodobenzene
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Treatment of alkenes and alkynes with diacetoxyiodobenzene activated by mineral and organic acids predominantly results in oxidative rearrangement. 1,4-Diphenylbutadiene in MeOH gives 3,4-dimethoxy-1,4-diphenylbut-1-ene.
- Yusubov,Zholobova,Filimonova,Chi, Ki-Whan
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p. 1735 - 1742
(2007/10/03)
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- Hydration of propargylic alcohols by ruthenium catalysts, with dominant anti-Markovnikov regioselectivity, formation of α,β-unsaturated products and catalytic decarbonylation to 1-alkenes
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Ruthenium catalysts - water-soluble ruthenium sulfophthalocyanine and heterogeneous ruthenium hydroxyapatite complexes - proved to be effective for the hydration of propargylic alcohols in entirely aqueous media. 1-Phenyl-2-propyn-1-ol underwent an unprecedented catalytic hydration- decarbonylation-dehydration reaction, giving rise to styrene and carbon monoxide; 2-propyn-1-ol and 3-butyn-2-ol gave predominantly the products of anti-Markovnikov addition, together with products of hydration-dehydration (α,β-rearrangement) and, to a minor extent, the decarbonylation products, ethene or propene, respectively. Hydrations were also conducted in D2O, giving indications of the mechanism of the reactions and apparently ruling out the allenylidene route for the α,β- rearrangement. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- D'Alessandro, Nicola,Di Deo, Milena,Bonetti, Monica,Tonucci, Lucia,Morvillo, Antonino,Bressan, Mario
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p. 810 - 817
(2007/10/03)
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- Reduction of 1,2-dicarbonyl compounds mediated by the combination of phosphine and lewis acid
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The combination of Ph3P/AlBr3 effectively promoted the reduction of several 1,2-dicarbonyl compounds in the presence of water (1.0 equiv) and the corresponding α-hydroxy carbonyl compounds were obtained in good yields.
- Kikuchi, Satoshi,Hashimoto, Yukihiko
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p. 1267 - 1269
(2007/10/03)
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- Hydrosilylation of cinchonidine and 9-O-TMS-cinchonidine with triethoxysilane: Application of 11-(triethoxysilyl)-10,11-dihydrocinchonidine as a chiral modifier in the enantioselective hydrogenation of 1-phenylpropane-1,2-dione
-
The detailed synthesis and characterization of (-)-11-(triethoxysilyl)-10,11-dihydrocinchonidine (4), a starting material for the immobilization of (-)-cinchonidine on silica based supports, is described. Compound 4 together with its precursors 9-O-(trime
- Lindholm, Anna,Maeki-Arvela, Paeivi,Toukoniitty, Esa,Pakkanen, Tapani A.,Hirvi, Janne T.,Salmi, Tapio,Murzin, Dmitry Yu.,Sjoeholm, Rainer,Leino, Reko
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p. 2605 - 2612
(2007/10/03)
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- Enantioselective hydrogenation of 1-phenyl-1,2-propanedione
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Enantioselective hydrogenation of a diketone, 1-phenyl-1,2-propanedione was studied in a pressurized reactor at 5 bar and at 0-25C in different solvents: ethanol, ethyl acetate, and dichloromethane over platinum catalysts. Both in situ modification (simultaneous addition of the reagent and the modifier) and pre-modification (preadsorption of the modifier prior to the reagent) of the catalyst were investigated using cinchonidine as catalyst modifier. Racemic hydrogenation proceeded with nearly the same rate as the selective hydrogenation in the presence of the catalyst modifier. The kinetic results revealed that the hydrogenation of the carbonyl group attached to the phenyl ring was preferred, the main product being 1-hydroxy-1-phenylpropanone; the ratio between 1-hydroxy-1-phenylpropanone and 2-hydroxy-1-phenylpropanone was about 11. The most effective and enantioselective catalyst was obtained by in situ modification in dichloromethane yielding in 67 mol% of (R)-1-hydroxy-1-phenylpropanone, corresponding to the enantiomeric excess of 64%. The enantiomeric excess was independent of the reactant conversion. In the second hydrogenation step the main product among diols was (1R,2S)-1-phenyl-1,2- propanediol.
- Toukoniitty, Esa,Maeki-Arvela, Paeivi,Kuzma, Marek,Villela, Alexandre,Kalantar Neyestanaki, Ahmad,Salmi, Tapio,Sjoeholm, Rainer,Leino, Reko,Laine, Ensio,Murzin, Dmitry Yu.
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p. 281 - 291
(2007/10/03)
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- Stereoselective Synthesis of Optically Active α-hydroxy Ketones and anti-1,2-diols via Asymmetric Transfer Hydrogenation of Unsymmetrically Substituted 1,2-diketones
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Formula Represented A well-defined chiral Ru catalyst RuCl(N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine)(η6-arene) effectively promotes asymmetric transfer hydrogenation of 1-aryl-1,2-propanedione with HCOOH/N(C2H5)3, leading preferentially to optically active 1-aryl-2-hydroxy-1-propanone with up to 99% ee and 89% yield at 10°C. The reaction at 40°C gives anti-1-aryl-1,2-propanediol with up to 95% ee and 78% yield. This is a highly efficient procedure for the synthesis of optically active anti-diols.
- Koike, Takashi,Murata, Kunihiko,Ikariya, Takao
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p. 3833 - 3836
(2007/10/03)
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- Reduction of 1,2-diketones with titanium tetraiodide: A simple approach to α-hydroxy ketones
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1,2-Diketones are readily reduced with titanium tetraiodide to give α-hydroxy ketones in good to excellent yields. Regioselectivity on the reduction of unsymmetrical substrates is also discussed. (C) 2000 Elsevier Science Ltd.
- Hayakawa,Sahara,Shimizu
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p. 7939 - 7942
(2007/10/03)
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- Asymmetric C-H oxidation of vic-diols to α-hydroxy ketones by a fructose-derived dioxirane: Electronic effects on the enantioselectivity of oxygen transfer
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A mechanistic study on the enantioselective C-H oxidation of vic-diols with the in-situ-generated dioxirane from the fructose-derived ketone 1 is presented. The asymmetrization of meso-configured and the kinetic resolution of racemic vic-diols 2 afforded the optically active α-hydroxy ketones 3 in opposite configurations with moderate to good ee values. Significant electronic effects on the enantioselectivity of C-H insertion have been observed, which are explained in terms of the hydrogen-bonded transition- state structures for the concerted C-H oxygen insertion.
- Adam, Waldemar,Saha-Moeller, Chantu R.,Zhao, Cong-Gui
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p. 7492 - 7497
(2007/10/03)
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- Asymmetric reduction of α-keto esters and α-diketones with a bakers' yeast keto ester reductase
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Optically pure α-hydroxy esters and α-hydroxy ketones have been synthesized by the reduction of the corresponding ketones with a keto ester reductase isolated from bakers' yeast (YKER-I). The reduction of α-keto esters affords the corresponding (S)- or (R)-hydroxy esters selectively, where the stereochemical course depends on the chain length of the alkyl substituent on the carbonyl group. An α-keto short alkanoic ester affords the corresponding (S)-hydroxy ester, whereas a long alkanoate yields the corresponding (R)-hydroxy ester. The reduction of α-diketones affords the corresponding (S)-2-hydroxy ketones regio- and stereoselectively.
- Kawai, Yasushi,Hida, Kouichi,Tsujimoto, Munekazu,Kondo, Shin-Ichi,Kitano, Kazutada,Nakamura, Kaoru,Ohno, Atsuyoshi
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- α-Trifluoromethylated acyloins induce apoptosis in human oral tumor cell lines
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Cytotoxic activity of newly synthesized trifluoromethyl ketones and related compounds was studied using two human oral tumor cell lines (HSG and HSC-2). Among them, α-trifluoromethylacyloins (1 and 2) were found to induce apoptotic cell death, as judged by the terminal deoxynucleotidyl transferase (TdT) dUTP nick end-labeling (TUNEL) method which detects DNA nick or fragments. Furthermore, the cytoplasm of 1 or 2 treated HSG cells was stained by M30 monoclonal antibody, which detects the product resulting from the cleavage of cytokeratin 18 by activated caspase.
- Kawase, Masami,Sakagami, Hiroshi,Kusama, Kaoru,Motohashi, Noboru,Saito, Setsuo
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p. 3113 - 3118
(2007/10/03)
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- Nucleophilic acylation of esters by acid chlorides mediated by samarium diiodide: Formation and use of samarium enediolates.
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Acid chlorides react with esters in the presence of samarium diiodide and catalytic amounts of NiI2 to afford samarium enediolates which can further react with electrophiles such as water or aldehydes to give respectively α-ketols or α-dihydroxyketones.
- Machrouhi, Fouzia,Namy, Jean-Louis,Kagan, Henri B.
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p. 7183 - 7186
(2007/10/03)
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- Fine regioselective tuning in the oxidation of sec,sec 1,2-diols by dimethyldioxirane
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Non-symmetric sec,sec 1,2-diols and their o-isopropylidene derivatives undergo a regioselective oxidation by dimethyldioxirane depending on the electronic effects of the substituents. These results support previous views about the concerted O-insertion mechanism via a polar transition state.
- Bovicelli, Paolo,Sanetti, Anna,Lupattelli, Paolo
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p. 10969 - 10978
(2007/10/03)
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- Catalytic osmylation of allenic compounds. Synthesis of α-hydroxyketo amino acid precursors
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Osmium tetroxyde-catalyzed dihydroxylation of allenic compounds in the presence of N-Methylmorpholine Oxide leads to α-ketols. Regioselectivity of this oxidation procedure with allenic α-amino acid precursors is greatly influenced by the nature and the remoteness of the protected amino acid group.
- David, Katerine,Ariente, Cecile,Greiner, Alfred,Gore, Jacques,Cazes, Bernard
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p. 3335 - 3338
(2007/10/03)
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- Efficient desymmetrization of 1,2 and 1,3 diols by dimethyldioxirane
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Dimethyldioxirane was used to monooxide 1,2 and 1,3 sec,sec-diols to the corresponding ketoalcohols, exploiting the inhibiting effect of the formed carbonyl group on the course of the process.
- Bovicelli, Paolo
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p. 3031 - 3034
(2007/10/02)
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- Reduction of Arylcarbonyl Using Zinc Dust in Acetic Acid
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Zinc dust in acetic acid has been found to be a versatile and chemoselective reagent for the reduction of various arylcarbonyls to the corresponding alcohols or their acetates in fair yields.
- Rani, B. Radha,Ubukata, Makoto,Osada, Hiroyuki
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p. 282 - 284
(2007/10/02)
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- Ion exchange resin-mediated hydrolytic cleavage of α-nitroepoxides. Simple one-pot synthesis of α-hydroxyketones
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α-Nitroepoxides are cleaved in an aqueous suspension with dowex-50 to furnish α-hydroxyketones in excellent yields.
- Chakraborty,Das,Ranu
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p. 1523 - 1528
(2007/10/02)
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- Highly Efficient Hydroxylation of Carbonyl Compounds with Dimethyldioxirane
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The enolates and/or enols of ketones, esters, β-diketones, β-oxo esters, and β-oxolactones were transformed by dimethyldioxirane (isolated in acetone solution or generated in situ) into their α-hydroxy compounds in good to excellent yields.The direct hydroxylation of the enols was significantly enhanced by the use of fluoride ion.For the enolate of camphor the exo/endo diastereoselectivity depended significantly on the metal ligand; the highest exo/endo ratio (93:7) was observed for the enol trimethylsilyl ether of camphor.Key Words: Dimethyldioxirane / Enolates / Hydroxylation / α-Hydroxy carbonyl compounds / Enol silyl ethers
- Adam, Waldemar,Prechtl, Frank
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p. 2369 - 2372
(2007/10/02)
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- Studies on Pyruvate Decarboxylase: Acyloin Formation from Aliphatic, Aromatic and Heterocyclic Aldehydes
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Evidence is described that supports the view that the enzyme responsible for acyloin formation from aldehydes in the yeast Saccharomyces cerevisiae is pyruvate decarboxylase.
- Crout, David H. G.,Dalton, Howard,Hutchinson, David W.,Miyagoshi, Masanori
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p. 1329 - 1334
(2007/10/02)
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- DEPROTECTION OF CARBONYL GROUPS BY ANODIC OXIDATION OF DITHIOACETALS: A KEY STEP IN THE SYNTHESIS OF α-DIONES, α-KETOLS AND CHIRAL SYNTHONS.
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The anodic oxidation of α-keto and α-hydroxythioacetals provides an efficient way for the regeneration of α-diones and α-ketols, specially in the cases where chemical reactions are unsuccessful.
- Martre, Anne-Marie,Mousset, Guy,Rhlid, Rachid Bel,Veschambre, Henri
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p. 2599 - 2602
(2007/10/02)
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- The chlorination of propiophenone; determination of pKa value and the course of the reaction
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Chlorination of propiophenone in alkaline aqueous solution lead to formation of α-hydroxypropiophenone as the first detectable intermediate; this undergoes slower oxidation to aromatic acids without any accumulation of further intermediates.From the rates of the initial chlorination we have been able to determine the pKa value as 17.56 +/- 0.51.Key words: propiophenone, chlorination, hydrolysis, rearrangement, pKa.
- Guthrie, J. Peter,Cossar, John
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p. 2060 - 2069
(2007/10/02)
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- Stereoselectrive Syntheses of Ephedrine and Related 2-Aminoalcohols of High Optical Purity from Protected Cyanohydrins
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Ephedrine and related optically active β-aminoalcohols can be prepared by zinc borohydride reduction of aryl O-protected magnesium imines and aryl α-hydroxyimimes which in turn are readily available from optically active cyanohydrins.
- Jackson, W. Roy,Jacobs, Howard A.,Matthews, Barry R.,Jayatilake, Gamini S.,Watson, Keith G.
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p. 1447 - 1450
(2007/10/02)
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- Applications of Optically Active Aryl Cyanohydrins in the Synthesis of α-Hydroxy Aldehydes, α-Hydroxy Ketones and β-Hydroxy Amines
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Cyanohydrins, prepared in high optical purity from aryl aldehydes, have been converted into α-hydroxy aldehydes, α-hydroxy ketones and β-hydroxy amines without any racemization and frequently with good stereoselectivity for the erythro-diastereoisomer (>90percent) at the newly introduced stereogenic centre.
- Jackson, W. Roy,Jacobs, Howard A.,Jayatilake, Gamini S.,Matthews, Barry R.,Watson, Keith G.
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p. 2045 - 2062
(2007/10/02)
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- MONO ET DIFLUORATION ELECTROCHIMIQUES DE GROUPES BENZYLIQUES
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Anodic oxidation of benzylic compounds 1 using CH3CN as a solvent and Et3N,3HF as a fluorinating reagent allowed to introduce a fluorine atom in α position of electron withdrawing group via carbocation 1+ (ECBECN mechanism).Whatever the E group, monofluorides 2 are obtained in good yields from paramethoxy derivatives 1 (R=p-OCH3).In this case, by raising the potential of working electrode after the monofluorination step, gem difluorides 3 can be directly prepared from 1.When the substituent of the phenyl ring is different of a methoxy group, a mixture of fluoride 2 and acetamide 4 is generally obtained and the ratio of these two compounds is related to cation stability.
- Laurent, Eliane,Marquet, Bernard,Tardivel, Robert
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p. 4431 - 4444
(2007/10/02)
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- New Reduction Method of α-Diketones, Oxo amides, and Quinones with Zn-EtOH in the Presence of a Salt
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The reagent, Zn-Salt-EtOH effectively reduces α-diketones, oxo amides, and quinones to hydroxy ketones, hydroxy amides, and hydroquinones, respectively.
- Toda, Fumio,Tanaka, Koichi,Tange, Hiroshi
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p. 1555 - 1556
(2007/10/02)
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- Radical Addition to the Carbonyl Carbon Promoted by Aqueous Titanium Trichloride: Stereoselective Synthesis of α,β-Dihydroxy Ketones
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Ketyl radicals, formed by chemoselective Ti(III) reduction of α,β-dicarbonyl compounds, add to the carbonyl carbon of aldehydes under mild conditions to afford α,β-dihydroxy ketones in good to excellent yields.Simple diastereoselectivity strongly depends on the bulk of groups bonded to both the ketyl radical and the aldehydic function.The relative configuration of two the keto diols was established by single-crystal X-ray diffractometry.
- Clerici, Angelo,Porta, Ombretta
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p. 3872 - 3878
(2007/10/02)
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- INFLUENCE OF ENOLATE GEOMETRY AND STRUCTURE ON THE STEREOCHEMISTRY OF THE ASYMMETRIC OXIDATION OF PROCHIRAL KETONE ENOLATES TO OPTICALLY ACTIVE α-HYDROXY KETONES
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The stereoselectivity for the asymmetric oxidation of enolates to optically active α-hydroxy ketones using (+)-(camphorylsulphonyl)oxaziridine is dependent on the enolate substitution pattern, the solution structure of the enolate and to a lesser extent the enolate geometry.
- Davis, Franklin A.,Sheppard, Aurelia C.,Lal, G. Sankar
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p. 779 - 782
(2007/10/02)
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