- Evidence for the HOOO- anion in the ozonation of 1,3-dioxolanes: Hemiortho esters as the primary products
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Low-temperature ozonation (-78 °C) of 2-methyl-1,3-dioxolane (1a) in acetone-d6, methyl acetate, and tert-butyl methyl ether produced both the corresponding acetal hydrotrioxide (3a, ROOOH) and the hemiortho ester (2a, ROH) in molar ratio 1:5. Both intermediates were fully characterized by 1H, 13C, and 17O NMR spectroscopy, and they both decomposed to the corresponding hydroxy ester at higher temperatures. The mechanism involving the HOOO- anion formed by the abstraction of the hydride ion by ozone to form an ion pair, R+ -OOOH, with its subsequent collapse to either the corresponding hemiortho ester (ROH) or the acetal hydrotrioxide (ROOOH) was proposed. This mechanism is supported by the PISA/B3LYP/6-311++G(3df,3pd) calculations. Copyright
- Plesnicar, Bozo,Cerkovnik, Janez,Tuttle, Tell,Kraka, Elfi,Cremer, Dieter
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Read Online
- The Mechanism of Formation of Ethylene Glycol Monoacetate from Ethylene in the System MeCO2H + LiNO3 + Pd(OAc)2
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A 17O n.m.r. study has shown that formation of ethylene glycol monoacetate from ethylene in acetic acid solution containing LiNO3 and Pd(OAc)2 is accompanied by oxygen atom transfer from the oxidant to the carbonyl group of the product.
- Kuznetsova, Nina I.,Likholobov, Vladimir A.,Fedotov, Martin A.,Yermakov, Yurii I.
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Read Online
- Poly(Ethylene Glycol) Dimethacrylates with Cleavable Ketal Sites: Precursors for Cleavable PEG-Hydrogels
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The authors introduce poly(ethylene glycol) (PEG) based macromonomers containing acid-labile ketal moieties as well as terminal methacrylate units that are amenable to radical polymerization. The synthesis of PEGs of different molecular weights (ranging from 2000 to 13 000 g mol?1 with polydispersities 1H NMR kinetic studies in deuterated phosphate buffer. Hydrogels containing 0, 5, or 10 wt% of PEG-ketal-DMA and 100, 95, or 90 wt% of PEG-DMA, respectively, are synthesized and disintegration of the gels is investigated in buffer at different pH values. Visible disintegration of the gels appears at pH 5 for hydrogels containing PEG-ketal-DMA, whereas no visible degradation is observed at all at neutral pH or for PEG hydrogels without PEG-ketal-DMA. (Figure presented.).
- Pohlit, Hannah,Leibig, Daniel,Frey, Holger
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Read Online
- Catalytic Hydrogenation of Thioesters, Thiocarbamates, and Thioamides
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Direct hydrogenation of thioesters with H2 provides a facile and waste-free method to access alcohols and thiols. However, no report of this reaction is documented, possibly because of the incompatibility of the generated thiol with typical hydrogenation catalysts. Here, we report an efficient and selective hydrogenation of thioesters. The reaction is catalyzed by an acridine-based ruthenium complex without additives. Various thioesters were fully hydrogenated to the corresponding alcohols and thiols with excellent tolerance for amide, ester, and carboxylic acid groups. Thiocarbamates and thioamides also undergo hydrogenation under similar conditions, substantially extending the application of hydrogenation of organosulfur compounds.
- Luo, Jie,Rauch, Michael,Avram, Liat,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 21628 - 21633
(2021/01/11)
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- A Reversible Liquid-to-Liquid Organic Hydrogen Carrier System Based on Ethylene Glycol and Ethanol
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Liquid organic hydrogen carriers (LOHCs) are powerful systems for the efficient unloading and loading molecular hydrogen. Herein, a liquid-to-liquid organic hydrogen carrier system based on reversible dehydrogenative coupling of ethylene glycol (EG) with ethanol catalysed by ruthenium pincer complexes is reported. Noticeable advantages of the current LOHC system is that both reactants (hydrogen-rich components) and the produced esters (hydrogen-lean components) are liquids at room temperature, and the dehydrogenation process can be performed under solvent and base-free conditions. Moreover, the hydrogenation reaction proceeds under low hydrogen pressure (5 bar), and the LOHC system has a relatively high theoretical gravimetric hydrogen storage capacity (HSC>5.0 wt %), presenting an attractive hydrogen storage system.
- Zhou, Quan-Quan,Zou, You-Quan,Ben-David, Yehoshoa,Milstein, David
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p. 15487 - 15490
(2020/10/02)
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- THIAZOLIDINONE COMPOUNDS AND USE THEREOF
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A pharmaceutical composition containing a compound of Formula (I) for treating an opioid receptor-associated condition. Also disclosed is a method for treating an opioid receptor-associated condition using such a compound. Further disclosed are two sets of thiazolidinone compounds of formula (I): (i) compounds each having an enantiomeric excess greater than 90% and (ii) compounds each being substituted with deuterium.
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Paragraph 1284-1285
(2017/09/21)
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- Synthesis of Mannosylglycerate Derivatives as Immunostimulating Agents
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Mannosylglycerate (MG) is a compatible solute extracted from some red algae and bacteria. Thanks to its ability to protect proteins and stabilise enzymes, MG has been widely studied for its uses against neurodegenerative diseases, and also in biotechnology. More recently, its immunostimulating properties against chronic lymphocytic leukaemia have been investigated. In this paper, we report the synthesis of MG derivatives, and a preliminary biological study on their capacity to behave as immunostimulating agents. We investigated their toxicity against peripheral blood mononuclear cells from healthy donors and their ability to increase the phagocytosis of opsonised bacteria by polynuclear neutrophils. This resulted in the discovery of two new molecules as potential immunostimulating agents.
- Hamon, Nadège,Mouline, Caroline C.,Travert, Marion
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p. 4803 - 4819
(2017/09/07)
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- Synthesis of acid-sensitive connection unit and its use in DNA sequencing
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The invention discloses a synthesis method of an acid sensitive connection unit, and a use of the acid sensitive connection unit in DNA sequencing. The structural formula of the acid sensitive connection unit is shown in the specification. In the structural formula, R is NH2 or N3, m is an integer from 0 to 44, and n is an integer from 0 to 44; R1 and R2 respectively represent an aliphatic alkyl group, or R1 and R2 respectively represent an aromatic derivative, or R1 is a phenyl group, a naphthyl group, a phenyl derivative or a naphthyl derivative, and R2 is an aliphatic alkyl group or hydrogen; or R2 is a phenyl group, naphthyl group, a phenyl derivative or a naphthyl derivative, R1 is an aliphatic alkyl group or hydrogen, or R1 and R2 form a cyclohexyl group, a cyclopentyl group or a cyclobutyl group. A reversible terminal obtained through connecting the acid sensitive connection unit with nucleotide and fluorescein can be used in DNA sequencing-by-synthesis. The reversible terminal can be used in the DNA sequencing; and raw materials required by the synthesis method are simple and can be easily obtained, and the synthesis process is a routine chemical reaction, so the method can realize large scale popularization use.
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Paragraph 0164-0168; 0322; 0342
(2018/02/04)
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- CYCLIC ORTHO ESTER FUEL ADDITIVE
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The invention relates to liquid hydrocarbons containing cyclic ortho esters as dehydrating dehydrating icing inhibitors and to methods of using the compounds. The liquid hydrocarbons include fuels such aviation fuels, lubricants, hydraulic fluids and hydrocarbon solvents.
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Paragraph 0111
(2016/04/20)
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- Conformational characteristics and configurational properties of poly(ethylene succinate) and poly(butylene succinate) and structure-property-function relationships of representative biodegradable polyesters
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Conformational characteristics and configurational properties of synthetic biodegradable polyesters, poly(ethylene succinate) and poly(butylene succinate), have been investigated by NMR experiments and molecular orbital calculations on their model compounds and the rotational isomeric state calculations for the two aliphatic polyesters. The results have been related to their crystal structures and thermal properties and compared with those obtained previously for poly((R)-3-hydroxybutyrate) and poly(lactic acid) to elucidate structureeproperty relationships of the representative biodegradable polyesters. In addition, selective affinities to degradative enzymes of the four polyesters have been satisfactorily explained in terms of their conformational characteristics and interactions with the depolymerases.
- Sasanuma, Yuji,Nonaka, Yuta,Yamaguchi, Yuki
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p. 327 - 339
(2015/03/03)
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- Carbodeoxygenation of biomass: The carbonylation of glycerol and higher polyols to monocarboxylic acids
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Glycerol is converted to a mixture of butyric and isobutyric acid by rhodium- or iridium-catalysed carbonylation using HI as the co-catalyst. The initial reaction of glycerol with HI results in several intermediates that lead to isopropyl iodide, which upon carbonylation forms butyric and isobutyric acid. At low HI concentration, the intermediate allyl iodide undergoes carbonylation to give vinyl acetic acid and crotonic acid. Higher polyols CnH n+2(OH)n are carbonylated to the corresponding C n+1 mono-carboxylic acids. Copyright
- Coskun, Timur,Conifer, Christopher M.,Stevenson, Laura C.,Britovsek, George J. P.
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supporting information
p. 6840 - 6844
(2013/07/05)
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- Design of a highly active silver-exchanged phosphotungstic acid catalyst for glycerol esterification with acetic acid
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A series of highly active, selective, and stable silver-exchanged phosphotungstic acid (AgPW) catalysts were prepared, characterized, and evaluated for bio-derived glycerol esterification with acetic acid to produce valuable biofuel additives. The structures, morphologies, acidities, and water tolerance of these samples were determined by FTIR, Raman, XRD, SEM-EDX, FT-IR of pyridine adsorption, and H2O-TPD. Several typical acidic catalysts were also performed for comparison. Among them, partially silver-exchanged phosphotungstic acid (Ag1PW) presented exceptionally high activity, with 96.8% conversion within just 15 min of reaction time and remarkable stability, due to the unique Keggin structure, high acidity as well as outstanding water-tolerance property. A plausible reaction mechanism was also proposed. In addition, this Ag1PW catalyst exhibited universal significance for esterification, holding great potential for a wide range of other acid-catalyzed reactions.
- Zhu, Shanhui,Gao, Xiaoqing,Dong, Fang,Zhu, Yulei,Zheng, Hongyan,Li, Yongwang
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p. 155 - 163
(2013/09/02)
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- A novel Bronsted acidic heteropolyanion-based polymeric hybrid catalyst for esterification
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A new SO3H-functionalized HPA-based acidic polymeric hybrid was prepared by coupling task-specifically designed SO3H-functionalized polymeric ionic liquid with Keggin-structured heteropolyanion, and characterized by 1H NMR, FT-IR, TG, XRD, BET, Hammett indicator, melting point, and elemental analysis. Its catalytic performance for esterification of alcohols with carboxylic acids was studied under solvent-free conditions. The results demonstrate that the polymeric hybrid is a highly active and selective solid catalyst for various esterifications, and can be easily recovered and steadily reused.
- Leng, Yan,Jiang, Pingping,Wang, Jun
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experimental part
p. 41 - 44
(2012/10/07)
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- Synthesis, characterization, and biocompatibility of biodegradable hyperbranched polyglycerols from acid-cleavable ketal group functionalized initiators
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Herein we report the synthesis of biodegradable hyperbranched polyglycerols (BHPGs) having acid-cleavable core structure by anionic ring-opening multibranching polymerization (ROMBP) of glycidol using initiators bearing dimethyl and cyclohexyl ketal groups. Five different multifunctional initiators carrying one to four ketal groups and two to four hydroxyl groups per molecule were synthesized. The hydroxyl carrying initiators containing one ketal group per molecule were synthesized from ethylene glycol. An alkyne-azide click reaction was used for synthesizing initiators containing multiple cyclohexyl ketal linkages and hydroxyl groups. The synthesized BHPGs exhibited monomodal molecular weight distributions and polydispersity in the range of 1.2 to 1.6, indicating the controlled nature of the polymerizations. The polymers were relatively stable at physiological pH but degraded at acidic pH values. The polymer degradation was dependent on the type of ketal structure present in the BHPG; polymers with cyclohexyl ketal groups degraded at much slower rates than those with dimethyl ketal groups at a given pH. Good control of polymer degradation was achieved under mild acidic conditions by changing the structure of ketal linkages. A precise control of the molecular weight of the degraded HPG was achieved by controlling the number of ketal groups within the core, as revealed from the gel permeation chromatography (GPC) analyses. The decrease in the polymer molecular weights upon degradation was correlated well with the number of ketal groups in their core structure. Our data support the suggestion that glycidol was polymerized uniformly from all hydroxyl groups of the initiators. BHPGs and their degradation products were highly biocompatible, as measured by blood coagulation, complement activation, platelet activation, and cell viability assays. The controlled degradation profiles of these polymers together with their excellent biocompatibility make them suitable for drug delivery and bioconjugation applications.
- Shenoi, Rajesh A.,Lai, Benjamin F. L.,Kizhakkedathu, Jayachandran N.
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p. 3018 - 3030,13
(2020/09/02)
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- Rational engineering of Candida antarctica lipase B for selective monoacylation of diols
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The enzyme Candida antarctica lipase B was subjected to site directed mutagenesis suggested by molecular modelling. The selectivity for the enzyme increased towards a range of diols over their corresponding monoesters as an effect of the mutations. This journal is The Royal Society of Chemistry 2012.
- Hamberg, Anders,Maurer, Steffen,Hult, Karl
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supporting information
p. 10013 - 10015
(2012/10/30)
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- SYNTHESIS OF ACETOXYACETALDEHYDE
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The invention belongs to the field of organic chemistry and relates to a new synthesis of acetoxyacetaldehyde. Comprising the steps of providing monoacetyl ethylene glycol and converting it by oxidation using an N-oxyl compound in the presence of a co-oxidant.
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Page/Page column 22
(2011/06/23)
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- Synthesis of acetoxyacetaldehyde
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The invention belongs to the field of organic chemistry and relates to a new synthesis of acetoxyacetaldehyde comprising the steps of providing monoacetyl ethylene glycol and converting it by oxidation using an N-oxyl compound in the presence of a co-oxidant.
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Page/Page column 15
(2011/06/23)
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- Kinetics and quantitative structure-activity relationships for pseudomonas sp. Lipase-catalyzed hydrolysis of both monoesters and diesters of ethylene glycol
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The goal of this work is to study kinetics and quantitative structure-activity relationships for steady states of Pseudomonas sp. lipase-catalyzed hydrolysis of both diesters and monoesters of ethylene glycol. Based on the steady-state kinetics of the enzyme-catalyzed hydrolysis of the diesters of ethylene glycol, the diesters and the monoesters react simultaneously as soon as monoester has started to build up in the reaction medium. In other words, the apparent Km values of the diesters are the Km values of the diesters (KmA) plus the Km values of the monoesters (KmB), and all Vmax values are about the same. Moreover, the pH-stat titration curve of the enzyme-catalyzed hydrolysis of the diesters of ethylene glycol is initially hyperbolic, then there is a sharp falloff in the hydrolysis rate. The abrupt stoppage of the reaction (relaxation stage) may be due to the existence of two phases in the reaction medium, that is, the product (ethylene glycol) and the substrates (the diesters of ethylene glycol) are not miscible. Furthermore, quantitative structure-activity relationships for varied acyl groups of mono- and diesters of ethylene glycol are studied. The fact that both pKmA and pK mB values are linearly correlated with the hydrophobicity constant (π) but not with the electronic substituent constants (σ*) indicates that the affinity of these substrates for the enzyme depends only on the hydrophobicitv of substrates. Copyright
- Chiou, Shyh-Ying,Cheng, Yu-Ru,Lu, Chun-Ping,Lin, Yan-Fu,Lin, Long-Yau,Lin, Gialih
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p. 201 - 207
(2007/10/03)
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- Low-temperature deacylation of N-monosubstituted amides
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(Chemical Equation Presented) The (PhO)3P-Cl2 reagent, prepared in situ by titrating a solution of triphenyl phosphite with chlorine, is used to convert N-monosubstituted amides into their corresponding amines. The reaction, if compared to other traditional methods, shows the advantage of very mild conditions and low temperature (-30°C→rt).
- Spaggiari, Alberto,Blaszczak, Larry C.,Prati, Fabio
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p. 3885 - 3888
(2007/10/03)
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- Production process for hydroxyalkyl (meth) acrylate
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There is disclosed a novel production process for a hydroxyalkyl (meth)acrylate in which: the diffusion of harmful substances due to disposal of catalysts can be reduced; and also the amount of the catalyst as used can be greatly saved in the entire production process. This production process comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide in the presence of a catalyst in order to produce the hydroxyalkyl (meth)acrylate; with the production process being characterized by further comprising the step of recovering the catalyst as has been used for the reaction.
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- Selective Monoacetylation of Symmetrical Diols and Selective Monodeacetylation of Symmetrical Diacetates Using HY-Zeolite as Reusable Heterogeneous Catalyst
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HY-Zeolite has been found to be an efficient and reusable catalyst for selective monoacetylation of symmetrical diols and selective monodeacetylation of symmetrical diacetates to form the products in high yields.
- Srinivas,Mahender,Das, Biswanath
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p. 2419 - 2421
(2007/10/03)
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- Oxidation of acetals by dimethyldioxirane
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Kinetic data (k2's, LFER and activation parameters) for the oxidation of a series of acetals by dimethyldioxirane to the corresponding esters in dried acetone are reported; the results are consistent with either a H-atom abstraction or direct insertion mechanism.
- Baumstark,Kovac, Franci,Vasquez, Pedro C.
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- Acyl iodides in organic synthesis: II. Reactions with acyclic and cyclic ethers
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Reaction of acyl iodides RCOI (R = Me, Ph) was studied with acyclic and cyclic ethers (Et2O, MeCHCH2(O), ClCH2CHCH 2(O), THF, O(CH2CH2)2O, EtOCH 2CH2OH, EtOCH=CH2, PhOEt]. The reaction occurred with the rupture of one or two CO bonds furnishing the corresponding iodides and esters.
- Voronkov,Trukhina,Vlasova
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p. 1579 - 1581
(2007/10/03)
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- Synthesis of monoprotected 1,4-diketones by photoinduced alkylation of enones with 2-substituted-1,3-dioxolanes
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Photosensitized hydrogen abstraction from 2-alkyl-1,3-dioxolanes by triplet benzophenone gives the corresponding 1,3-dioxolan-2-yl radicals and these are trapped by α,β-unsatured ketones yielding monoprotected 1,4-diketones. With open chain ketones (3-buten-2-one and 4-penten-3-one) the yields are low and competitive pathways in part consume the radicals. With cyclic enones however, yields are good as tested with cyclopentenone, cyclohexenone and 4-hydroxy-cyclopentenone. More generally, this is a viable alternative for the synthesis of 1,4-diketones via radicals while the thermal initiation gives only low yield. The reaction cannot be extended to strongly stabilized radicals, such as the 2-phenyl-1,3-dioxolanyl radical.
- Mosca, Raffaella,Fagnoni, Maurizio,Mella, Mariella,Albini, Angelo
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p. 10319 - 10328
(2007/10/03)
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- The synthesis of highly reactive, multi-functional α,β-epoxy- and α-acetoxy-nitrosamines
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The synthesis of the reactive acetates, trans-3-acetoxy-2-hydroxy-N-nitrosomorpholine 3 and N-(1-acetoxy-2-hydroxyethyl)-N-nitrosoethanolamine 12, of two α-hydroxynitrosamines has been accomplished through the ring opening of the corresponding epoxides, NEMOR and 10 which were prepared by dimethyldioxirane oxidation of the vinyl nitrosamines.
- Park, Misun,Gu, Feng,Loeppky, Richard N.
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p. 1287 - 1290
(2007/10/03)
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- OH radical initiated photooxidation of 2-ethoxyethanol under laboratory conditions related to the troposphere: Product studies and proposed mechanism
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The products formed by the hydroxyl radical-initiated oxidation of 2- ethoxyethanol (CH3CH2OCH2CH2OH) have been investigated by irradiating synthetic air mixtures containing the substrate, methyl nitrite, and nitric oxide at ppm levels in a Teflon bag reactor at room temperature. The decay of reactants and the formation of products were monitored by gas chromatography and mass spectrometry. The major products ethyl formate [HC(O)OCH2CH3], ethylene glycol monaformate [HC(O)OCH2CH2OH], ethylene glycol monaacetate [CH3C(O)OCH2CH2OH], and ethoxyacetaldehyde [CH3CH2OCH2C(O)H] give a quantitative mass balance with the decay of the substrate molecule. The yields of these products were 34 ± 10%, 36 ± 7%, 7.8 ± 2.4%, and 24 ± 13%, respectively, in terms of percent of 2-ethoxyethanol removed by the OH radical. The product distribution is explained by a mechanism involving initial OH attack at the three CH2 groups in 2-ethoxyethanol followed by the subsequent reactions of the resulting alkyl and alkoxy radicals. The decomposition reactions of the alkoxy radicals from 2-ethoxyethanol, which can take place either by C-C or C-O bond breaking, involve preferential C-C cleavage rather than C-O cleavage. Rate coefficients at room temperature for the reactions of OH radicals with ethoxyacetaldehyde and 2-methyl-1,3- dioxolane (CH3CHOCH2CH2O, a minor product) have been determined to be 16.6 x 10-12 and 9.4 x 10-12 cm3 molecule-1 s-1, respectively.
- Stemmler, Konrad,Mengon, Wolfgang,Kerr, J. Alistair
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p. 3385 - 3391
(2007/10/03)
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- Radicals through Photoinduced Electron Transfer. Addition to Olefin and Addition to Olefin-Aromatic Substitution Reactions
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The radical cations of 2,2-dialkyl- and 2-alkyl-2-aryl-1,3-dioxolanes, when generated in solution by photoinduced electron transfer to 1,2,4,5-benzenetetracarbonitrile (TCB), fragment to yield alkyl radicals.These are trapped by electron-withdrawing substituted alkenes (acrylonitrile, methyl acrylate, methyl vinyl ketone, as well as dimethyl maleate and fumarate).The radicals thus formed are either reduced by the TCB radical anion or add to it.In the first process (observed only with the diesters) the end result is reductive alkylation of the olefin, while the latter process results in an addition to the olefin-aromatic substitution reaction.The selectivity of the process is explained on the basis of steric hindrance, since the radicals react when still in the cage with the aromatic radical anion.
- Mella, Mariella,Fagnoni, Maurizio,Albini, Angelo
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p. 5614 - 5622
(2007/10/02)
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- Unique Template Effects of Distannoxane Catalysts in Transesterification of Diol esters
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1,n-Diol diacetates (n = 2,3,4) are selectively converted into the corresponding monoacetates by distannoxane-catalyzed transesterification.Such unique selectivity is not encountered with 1,n-diol diacetates where n>/=5.A great difference in reactivity is also seen in the transesterification between methyl butyrate and 1,n-diol monoacetates: the ethylene glycol derivative sluggishly undergoes transesterification whereas higher homologs react smoothly.The unique template effects of the catalysts are discussed in terms of cooperation of two different tin atoms which are located in the proximity.
- Otera, Junzo,Dan-oh, Nobuhisa,Nozaki, Hitosi
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p. 3065 - 3074
(2007/10/02)
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- Reactions of 1,3-dioxolanes with Iodine Monochloride: Formation of Chlorohydrin Esters and Diol Monoesters
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2-Mono-substituted 1,3-dioxolanes are oxidised by iodine monochloride to the appropriate 2-substituted 1,3-dioxolan-2-ylium ions, whose stability is dependent upon the presence and nature of substituents on C-4 and C-5.Some dioxolanylium ions are labile and under the reaction conditions afford chlorohydrin esters, with inversion of configuration taking place at the ring carbon attacked by chloride.Others are stable under the reaction conditions and may be converted on aqueous workup to diol monoesters with retention of configuration at C-4 and C-5.The effect of substituents and reaction conditions on these competing reactions are described.The stereo- and regio-chemistry of both hydroxy- and chloro-ester formation was confirmed through NMR studies, which necessitated the prior detailed analysis of the 1H and 13C spectra associated with the acyloxy sidechains of the relevant esters.
- Glass, Beverley D.,Goosen, Andre,McCleland, Cedric W.
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p. 2175 - 2182
(2007/10/02)
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- Electron Transfer Photoinduced Cleavage of Acetals. A Mild Preparation of Alkyl Radicals
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Electron transfer from 2-alkyl- and 2,2-dialkyldioxolanes as well as from open-chain ketals to singlet excited benzene-1,2,4,5-tetracarbonitrile (TCNB) is followed by fragmentation of the donors radical cation to yield alkyl radicals and dialkoxy carbocations.The first species are trapped by TCNB to yield alkylbenzenetricarbonitriles (substitution of a second cyano group can be obtained sequentially) and in a minor path are reduced to alkanes, while the latter ones react with nucleophiles to give ortho acid derivatives.In view of the results of radical clock experiments, it is assumed that part of the process is a concerted (radical cation cleavage-addition to the aromatic) reaction, while another part involves the free-radical cation.On the other hand, intersystem crossing from the singlet radical ion pair to the triplet manifold causes cleavage of the acetal to the corresponding carbonyl derivative.This reaction offers a mild method for the preparation of alkyl radicals via C-C bonds cleavage.
- Mella, M.,Fasani, E.,Albini, A.
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p. 3051 - 3057
(2007/10/02)
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- Highly Selective Monoacylation of Symmetric Diols Catalyzed by Metal Sulfates Supported on Silica Gel
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Several 1,α-diols, ranging from 1,2-ethanediol to 1,16-hexadecanediol, were monoacylated with high selectivity by reaction with esters in the presence of metal sulfates or hydrogen sulfates, like Ce(SO4)2 and NaHSO4, supported on silica gel.Symmetrical secondary diols were also selectively monoformylated, by reaction with ethyl formate.This method of selective esterification is simple and practical.The yield of monoester depends upon both the composition and the volume of the solvent (an ester/alkane mixture).Unsupported NaHSO4 also catalyzed monoacylation, but the selectivity was less than in monoacylations catalyzed by the supported reagent.The selectivity can be explained by the following reasons: (1) monoacylated products are formed selectively because the diol, but not the monoester, is preferentially adsorbed on the surface of the catalysts, where esterification then occurs, and (2) thin diol layers are formed on the surface of the catalysts due to limited solubility of the diols in the solvent.
- Nishiguchi, Takeshi,Kawamine, Katsumi,Ohtsuka, Tomoko
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p. 312 - 316
(2007/10/02)
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- Regio- and stereoselective transacylation of polyhydric alcohols using pronase in organic solvents
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Pronase a mixture of proteases from Streptomyces griseus has been found to be a good catalyst for transacylation in organic solvents.With equimolar concentrations of p-nitrophenyl acetate as acyl donor in pyridine, aliphatic diols give predominantly the monoacetates.Glucose and isomeric hexoses give the 6-O-acetates in good yield. 6-Deoxy-sugars however, yield mixtures of acetates indicating that regioselectivity among the secondary hydroxyl groups are poor.Racemic trans-1,2-cyclohexanediol affords the (1R, 2R)-monoacetate in 44percent yield with greater than 90percent enantiomer ic purity. cis-1,2-cyclohexanediol and cis-1,2-cyclohexanedimethanol also give optically active monoacetates.
- Bhattacharya, A,Ali, E
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p. 898 - 899
(2007/10/02)
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- Distannoxane-catalyzed Transesterification of 1,n-Diol Diacetates. Selective Transformation of Either of Chemically Equivalent Functional Groups
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Using catalysis by 1,3-dichlorotetrabutyldistannoxane, 1,n-diol diacetates were selectively converted into the corresponding monoacetates.
- Otera, Junzo,Dan-Oh, Nobuhisa,Nozaki, Hitosi
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p. 1742 - 1743
(2007/10/02)
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- Oxidation of Cyclic Acetals as a Preparative Method of Diol Monoester Production
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Glycol monoesters were produced by oxidation of acetals with oxygen, hydroperoxides, hydrogen peroxide, hydrotrioxide and ozon.Addition of salts of metals of variable valency and crown-ether substantially increase the rate of oxidation and hydroxylation.The most efficient oxidizer is ozon.
- Kuramshin, E. M.,Kulak, L. G.,Nazarov, M. N.,Zlotsky, S. S.,Rakhmankulov, D. L.
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p. 591 - 599
(2007/10/02)
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- Alkyl Group Effects on the Rate Constants and Equilibrium Constants for Formation of Cyclic Tetrahedral Intermediates
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2-Hydroxy-2-alkyl-1,3-dioxolanes T are the cyclic intermediates of the degenerate intramolecular ester interchange reactions of ethylene glycol monoalkanoates A, in which alkanoyl groups transfer from one end of ethylene glycol to the other.This study reports equilibrium constants for the cyclization AT to the tetrahedral intermediate stage with 10 alkanoate derivatives.These equiilibrium constants, which when written as / are all large (1 E7-1 E9) in favor of the ring opened form, were obtained as the ratio of rate constants for equilibration occuring with H+ catalysis.Rate constants for the ring opening of T were directly measured through a study of kinetics of the hydrolysis of 2-methoxy-2-alkyl-1,3-dioxolane ortho esters.These hydrolysis proceed via T, and under acid conditions the breakdown of this intermediate is rate-limiting.Rate constants in the ring-closing direction were obtained by preparing HOCH2CD2OOCR and, with the use of 1H NMR spectroscopy, measuring the kinetics of isomerization to an equilibrium mixture with RCOOCH2CD2OH.The reaction under investigation is an intramolecular analogue of H+-catalyzed alkanoate ester hydrolysis, whose rate constant define the steric substituent parameter Es.The ring-closure rate constant for A -> T do show an excellent correlation with Es.However, the rate constants for ring-opening T -> A and the overall equilibrium constant are badly correlated, showing quite different behavior for series with α and β branching in the alkyl group.Thus, for this system the Es parameter does not correlate free energy differencies between the acyl derivative and tetrahedral intermediate.It is only the free energy differences between the acyl form and the transition state leading to the intermediate that fit Es.
- Santry, Linda J.,Azer, Salwa,McClelland, Robert A.
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p. 2909 - 2914
(2007/10/02)
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- NOVEL REACTIVITY OF 2-(CHLOROMETHOXY)ETHYL ACETATE
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2-(Chloromethoxy)ethyl acetate reacts with alcohols in the presence of silver carbonate to produce 2-(alkoxymethoxy)ethyl acetates and bis(alkoxy)methanes.A mechanism which involves neighboring group participation of a chloromethyl ether oxygen atom is proposed to account for the formation of the latter products.
- Aitken, David J.,Rees, Lilias,Suckling, Colin J.,Wood, Hamish C. S.
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p. 3417 - 3420
(2007/10/02)
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- SYNTHESIS AND DECOMPOSITION OF THE HYDROTRIOXIDES OF 1,3-DIOXOLANES
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The hydrotrioxides of 1,3-dioxolane and 2-methyl-1,3-dioxolane were synthesized.Their thermal decomposition leads to the formation of glycol monoesters.The hydrotrioxides exhibit high oxidizing activity and oxidize the initial cyclic acetal to the corresponding monoester.The possibility of using hydrotrioxides as oxidizing agents for organic substances such as phosphines and sulfides was examined.
- Kuramshin, E. M.,Kulak, L. G.,Zlot-skii, S. S.,Rakhmankulov, D. L.
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p. 1783 - 1786
(2007/10/02)
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- Formation of Glycol Monoacetates in the Oxidation of Olefins Catalyzed by Metal Nitro Complexes: Mono- vs. Bimetallic System
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The oxidation of terminal olefins by bis(acetonitrile)chloronitropalladium(II) (1) in acetic acid leads to a mixture of glycol monoacetate isomers as the main products.Various amounts of ketones and unsaturated acetates are also formed.The rate of formation and the yield of glycol monoacetate decrease with increasing chain length.Cyclic olefins yield no glycol monoacetates.Replacement of acetic acid by stronger or sterically hindered carboxylic acids completely eliminates the formation of glycol monocarboxylates.Introduction of oxygen converts this stoichiometric reaction into a catalytic system.Our studies, including those carried out with complex 1 labeled with 18O in the nitro ligand, suggest that the glycol monoacetates and most of the ketones are the product of oxygen atom transfer from the nitro group, while the unsaturated acetates are the result of a Wacker-type reaction.In the glycol monoacetate, the 18O label is found exclusively in the acetate group.A mechanism which is in agreement with the above observations as well as a comparison of the above reaction with the oxidation of olefins by nitrate ions in the presence of palladium(II) salts is offered.The formation of glycol monoacetates in the monometallic system represented by complex 1 is to be compared with the results obtained in the bimetallic systems consisting of a combination of py(TPP)CoNO2 and either (CH3CN)2PdCl2 or Pd(OAc)2.In the latter systems, ketones or vinyl acetates are found as the predominant products.This fact underlines the difference between the mono- and bimetallic systems and strongly argues against alternative mechanisms involving nitro group transfer from cobalt to palladium before the olefin oxidation takes place.Additional evidence underlining the difference between these two systems is presented.
- Mares, Frank,Diamond, Steven E.,Regina, Francis J.,Solar, Jeffrey P.
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p. 3545 - 3552
(2007/10/02)
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- Deacylation of Pyrrole and other Aromatic Ketones
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Ethyl 4-acetyl-3,5-dimethyl-1H-pyrrole-2-carboxylate (1a) reacts rapidly with ethylene glycol in refluxing benzene with p-toluenesulfonic acid or perchloric acid as a catalyst to give ethyl 3,5-dimethyl-1H-pyrrole-2-carboxylate (3) in high yield (96 percent).Various 2- and 3-acylpyrroles can be efficiently deacylated by using this procedure.Other ketones which undergo deacylation include phenyl(2-phenylindol-3-yl)methanone (19), 1-(5-methyl-1-phenylpyrazol-4-yl)ethanone (20), and 2,4-dimethoxybenzophenone.Certain pyrrole ketones where the acyl group is flanked by two ring methyl groups are also cleaved under acidic conditions by using ethanedithiol.
- Moon, M. W.,Wade, R. A.
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p. 2663 - 2669
(2007/10/02)
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- Selective Production of C2-Oxygenate Esters from Synthesis Gas using Mixed Metal Homogeneous Catalysts
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C2-Oxygenate esters, particularly ethylene glycol diacetate, may be prepared in high selectivity directly from synthesis gas in the presence of composite homogeneous catalysts which contain mixtures of ruthenium and rhodium, as major and minor components respectively, together with promoters in the form of nitrogen-containing bases or alkali metal cations, in acetic acid as solvent.
- Whyman, Robin
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p. 1439 - 1441
(2007/10/02)
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- The Chemistry of Nitrilium Salts. Part 2. The Preparation of Nitrilium Trifluoromethanesulphonate Salts and Their Reactions with Some Oxygen and Sulphur Nucleophiles
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The syntheses of the nitrilium salts NMe>+3SCF3 i, PhCH2, Ph, CH2=CHCH2, NC(CH2)3, and CH2=CH> by reaction of MeO3SCF3 with the corresponding nitriles are described. the similar reaction between (E)-PhCH=CHCN and MeO3SCF3 gives a mixture of NMe>+SCF3 and the s-triazinium salt 3C3N3H>+3SCF3, which hydrolyzes to give (E)-PhCH=CHCONHMe and the triazine.The compound CF3SO3(CH2)4CN, prepared from I(CH2)4CN and AgO3SCF3, does not form a cyclic nitrilium salt, but slowly dimerizes at room temperature to N(CH2)4CN>+3SCF3.Both I(CH2)4CN and CF3SO3(CH2)4CN can be converted into the salt NMe>+3SCF3, but this does not form a dinitrilium salt on reaction with acetonitrile.On heating benzophenone oxime with CF3SO3H Beckmann rearrangement products are obtained, but conversion of +SCF3 into the nitrilium salt NPh>*3SCF3 ocuurs in only low yield even after 8 h at 130 deg C under high vacuum.The nitrilium salts with R = Ph, Me, Pri, and PhCH2 undergo rapid exothermic reaction with phenol, thiophenol, alcohols, and thiols to give the corresponding imidate and thioimidate salts in high yields. 4,4-Dimethy-2-phenyl-1,3-oxazoline is obtained in 74percent yield on heating NMe>+*3SCF3 with H2NCMe2CH2OH, and both this and 2,4,4-trimethyloxazoline react with MeO3SCF3 to give almoust quantitative yields of the corresponding N-methyloxazolinium salts, which can be reduced to the oxazolidines with NaBH4.N-Methyloxazolinium salts have also been obtained from the reactions of nitrilium salts (R = Ph or Me) with ethylene oxide.
- Booth, Brian L.,Jibodu, Kehinde O.,Proenca, M. Fernanda J. R. P.
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p. 1067 - 1073
(2007/10/02)
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