- Conversion of 2-Methylfuran to 2-Methylthiophene over Molecular Sieves. Part 1. - Alkaline Y-Zeolites
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The use of MeI Y zeolites (MeI = Li, Na, K, Rb, Cs) for the title reaction has been studied at 623 K and atmospheric pressure, looking at the effect of the nature of monovalent alkali-metal ions on both physico-chemical and catalytic properties of the resulting catalyst.The catalyst is very active and selective and, after ageing, it can be regenerated quite easily by a proper redox treatment.Besides the desired product, small amounts to traces of ca. 30 byproducts were detected, the structure of which can be explained only by admitting two different parallel reactions, one based on a ionic-type and the other on a radical-type mechanism.Some hypotheses are proposed on the possible start-up of such mechanisms, based on different adsorption modes of H2S onto the catalyst surface.
- Ferino, Italo,Monaci, Roberto,Solinas, Vincenzo,Oliva, Cesare,Pieri, Ilaria,Forni, Lucio
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Read Online
- Gas-phase pyrolysis of thiopheneacetic acids, thienylethanols, and related compounds - Protophilicity of ring π-electrons and relative acidities of hydrogen-bond donors of hydroxyl groups
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Based on kinetic data of thermal gas-phase elimination reactions, the following Arrhenius log A (s-1) and Ea (kJ mol-1) values, respectively, are obtained: 10.76 and 153.5 for 3-thiopheneacetic acid (1), 10.08 and 149.4 for 2-thiopheneacetic acid (2), 12.04 and 207.1 for 2-(3-thienyl)ethanol (3), 11.55 and 203.3 for 2-(2-thienyl)ethanol (4), 10.91 and 123.4 for 2-thiopheneglyoxylic acid (5), 11.05 and 223.8 for 1-(2-thienyl)propan-1-one (6), and 10.33 and 149.8 for 3-thiophenemalonic acid (7). The products of these pyrolytic reactions were either carbon dioxide or formaldehyde in addition to methylthiophene or thiophenecarboxaldehyde. Both positional and molecular reactivities of the substrates and related compounds are compared, and the results are rationalized on the basis of a reaction pathway involving a concerted six-membered transition state.
- Al-Juwaiser, Ibtehal A.,Al-Awadi, Nouria A.,El-Dusouqui, Osman M.E.
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Read Online
- Iodothiophenes and Related Compounds as Coupling Partners in Copper-Mediated N-Arylation of Anilines
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N-Arylation of various 2-acylated anilines with different electron-rich heteroaryl iodides (2- A nd 3-iodothiophenes, 2- A nd 3-iodobenzothiophenes?-, 2-iodobenzofuran) was achieved by using activated copper and potassium carbonate in dibutyl ether at reflux. The reactivity of the different heteroaryl iodides and anilines employed was discussed and rationalized on the basis of their electronic features. Subsequent cyclization by aromatic electrophilic substitution easily took place in the case of C2-free (benzo)thienyl or C3-free (benzo)furyl derivatives?-, affording original tri- A nd tetracycles. The antiproliferative activity of most of them was evaluated in A2058 melanoma cells and revealed four chlorinated tetracycles as effective growth inhibitors.
- Bouarfa, Salima,Bentabed-Ababsa, Ghenia,Erb, William,Picot, Laurent,Thiéry, Valérie,Roisnel, Thierry,Dorcet, Vincent,Mongin, Florence
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p. 1271 - 1284
(2020/11/09)
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- Iodine-catalyzed alcohol disproportionation method
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The invention relates to the technical field of catalysis, in particular to an iodine-catalyzed alcohol disproportionation method which comprises the following steps: sequentially adding alcohol, iodine and a solvent into a high-temperature and high-pressure reaction kettle, introducing a certain amount of nitrogen, conducting reacting for a certain time, collecting an organic phase after the reaction is ended, and conducting fractionating to obtain corresponding alkane and aldehyde/ketone. Alcohol disproportionation is efficient and atom-economical conversion without any additional oxidizing agent and reducing agent, and hydrocarbon and aldehyde/ketone molecules which are easy to separate can be formed at the same time. Meanwhile, the method has wide functional group tolerance, various substrate samples including aryl alcohol derivatives, heterocyclic alcohol derivatives, allyl alcohol derivatives and dihydric alcohol are tested, and the result shows that most of the substrate samples show good or extremely good yield.
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Paragraph 0042-0043
(2021/06/13)
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- Aerobic Self-Esterification of Alcohols Assisted by Mesoporous Manganese and Cobalt Oxide
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Aerobic self-esterification of primary alcohols catalyzed by mesoporous metal oxides (manganese and cobalt oxides) is reported under base and solvent free conditions. For a range of aliphatic alcohols, up to 90 % conversions to esters was achieved. The catalytic reaction is likewise applicable to neat aldehydes as substrates with yields of up to 86 %. High pressure batch reaction for ethanol to ethyl acetate led to 22 % yield. Isotope labeling studies indicated decarboxylation on the catalyst surface. Mechanistic and kinetic experiments implicate oxygen rebound and α-carbon removal as intermediate steps. Mesoporous cobalt oxide showed about 20 % higher catalytic activity compared to mesoporous manganese oxide.
- Moharreri, Ehsan,Biswas, Sourav,Deljoo, Bahareh,Kriz, David,Lim, Seyoung,Elliott, Sarah,Dissanayake, Shanka,Dabaghian, Marina,Aindow, Mark,Suib, Steven L.
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p. 3413 - 3422
(2019/08/01)
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- Catalytic hydrodebromination of aryl bromides by cobalt tetra-butyl porphyrin complexes with EtOH
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Hydrodebromination of aryl bromides catalyzed by electron rich and sterically unhindered cobalt 5,10,15,20-tetrabutylporphyrin was achieved at mild conditions in good yields employing EtOH as the hydrogen source. The catalytic efficiency was enhanced compared with previously reported by cobalt tetra-aryl porphyrin catalysts. A revised mechanism of single electron transfer was proposed.
- Chen, Chen,Zuo, Huiping,Chan, Kin Shing
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p. 510 - 517
(2019/01/04)
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- On/Off O2 Switchable Photocatalytic Oxidative and Protodecarboxylation of Carboxylic Acids
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Photoredox catalysis in recent years has manifested a powerful branch of science in organic synthesis. Although merging photoredox and metal catalysts has been a widely used method, switchable heterogeneous photoredox catalysis has rarely been considered. Herein, we open a new window to use a switchable heterogeneous photoredox catalyst which could be turned on/off by changing a simple stimulus (O2) for two opponent reactions, namely, oxidative and protodecarboxylation. Using this strategy, we demonstrate that Au@ZnO core-shell nanoparticles could be used as a switchable photocatalyst which has good catalytic activity to absorb visible light due to the localized surface plasmon resonance effect of gold, can decarboxylate a wide range of aromatic and aliphatic carboxylic acids, have multiple reusability, and are a reasonable candidate for synthesizing both aldehydes/ketones and alkane/arenes in a large-scale set up. Some biologically active molecules are also shown via examples of the direct oxidative and protodecarboxylation which widely provided pharmaceutical agents.
- Bazyar, Zahra,Hosseini-Sarvari, Mona
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p. 13503 - 13515
(2019/10/11)
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- Method for separating components in mixture containing methylbenzene, 2-methylthiophene and 3-methylthiophene
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The invention belongs to the technical field of chemical engineering, and particularly relates to a method for separating components in a mixture containing methylbenzene, 2-methylthiophene and 3-methylthiophene. According to the method, 2-methylthiophene and 3-methylthiophene in the mixture containing methylbenzene, 2-methylthiophene and 3-methylthiophene with very close boiling points are converted into substances 2-chloro-5-methylthiophene and 2,5-dichloro-3-methylthiophene with boiling points greatly different from the boiling point of methylbenzene by adopting a chemical method for the first time; then the components are separated and purified by adopting a rectification method, and the 2-chloro-5-methylthiophene and the 2,5-dichloro-3-methylthiophene are treated by adopting a reduction method and the like to obtain single-component 2-methylthiophene and 3-methylthiophene, so that the methylbenzene, the 2-methylthiophene and the 3-methylthiophene are separated. The method is simple in process, high in product yield and purity, good in separation effect, low in energy consumption and free of emission of three wastes(waste gas, waste water and industrial residues), and is a green separation process.
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Paragraph 0052; 0053; 0054; 0055
(2019/12/09)
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- Photocatalytic carbanion generation-benzylation of aliphatic aldehydes to secondary alcohols
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We present a redox-neutral method for the photocatalytic generation of carbanions. Benzylic carboxylates are photooxidized by single electron transfer; immediate CO2 extrusion and reduction of the in situ formed radical yields a carbanion capable of reacting with aliphatic aldehydes as electrophiles giving the Grignard analogous reaction product.
- Donabauer, Karsten,Maity, Mitasree,Berger, Anna Lucia,Huff, Gregory S.,Crespi, Stefano,K?nig, Burkhard
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p. 5162 - 5166
(2019/06/05)
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- Catalytic Synthesis of Methylthiophenes
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The gas-phase reaction of dimethyl disulfide with thiophene over Co/HZSM-5 catalyst in a helium medium under atmospheric pressure at 250–350°C gave a mixture of mono-, di-, tri-, and tetramethylthiophenes with an overall selectivity of 94–96%.
- Mashkina,Khairulina
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p. 1794 - 1797
(2019/03/26)
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- En Route to a Practical Primary Alcohol Deoxygenation
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A long-standing scientific challenge in the field of alcohol deoxygenation has been direct catalytic sp3 C-O defunctionalization with high selectivity and efficiency, in the presence of other functionalities, such as free hydroxyl groups and amines widely present in biological molecules. Previously, the selectivity issue had been only addressed by classic multistep deoxygenation strategies with stoichiometric reagents. Herein, we propose a catalytic late-transition-metal-catalyzed redox design, on the basis of dehydrogenation/Wolff-Kishner (WK) reduction, to simultaneously tackle the challenges regarding step economy and selectivity. The early development of our hypothesis focuses on an iridium-catalyzed process efficient mainly with activated alcohols, which dictates harsh reaction conditions and thus limits its synthetic utility. Later, a significant advancement has been made on aliphatic primary alcohol deoxygenation by employing a ruthenium complex, with good functional group tolerance and exclusive selectivity under practical reaction conditions. Its synthetic utility is further illustrated by excellent efficiency as well as complete chemo- and regio-selectivity in both simple and complex molecular settings. Mechanistic discussion is also included with experimental supports. Overall, our current method successfully addresses the aforementioned challenges in the pertinent field, providing a practical redox-based approach to the direct sp3 C-O defunctionalization of aliphatic primary alcohols.
- Dai, Xi-Jie,Li, Chao-Jun
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supporting information
p. 5433 - 5440
(2016/05/19)
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- On the Route to the Photogeneration of Heteroaryl Cations. the Case of Halothiophenes
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2-Chloro-, 2-bromo-, and 2-iodothiophenes undergo photochemical dehalogenation via the triplet state. In the presence of suitable π-bond nucleophiles, thienylation occurs with modest yield from chloro and bromo derivatives (via photogenerated triplet 2-thienyl cation). Specific trapping by using oxygen along with computational analysis carried out by means of a density functional method support that, in the case of iodo derivatives, homolytic thienyl-I bond fragmentation occurs first and heteroaryl cations are formed by electron transfer within the triplet radical pair, thus opening an indirect access to such cations.
- Raviola, Carlotta,Chiesa, Francesco,Protti, Stefano,Albini, Angelo,Fagnoni, Maurizio
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p. 6336 - 6342
(2016/08/16)
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- Tandem thionation of biomass derived levulinic acid with Lawesson's reagent
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Herein we report a tandem thionation of biomass derived levulinic acid (LA) to generate thiophenic compounds. LA is initially converted to several thiophenones and then an aromatic di-thionated product, 5-methylthiophene-2-thiol, is obtained with the highest yield of 78%. An overall synthesis of thiophenic products from cellulose is also developed.
- Li, Zheng,Tang, Xing,Jiang, Yetao,Zuo, Miao,Wang, Yangjun,Chen, Wei,Zeng, Xianhai,Sun, Yong,Lin, Lu
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p. 2971 - 2975
(2016/06/06)
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- Catalytic reactions of dimethyl disulfide with thiophene and benzene
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The gas-phase reaction of dimethyl disulfide with thiophene proceeds under the action of acid catalysts under atmospheric pressure at 160-350°C and a residence time of τ = 0.6-21 s to form thioalkylation and alkylation products. Dimethyl disulfide reacts with benzene to form only alkylation products. Catalysts containing both strong protic and Lewis acid sites, as well as basic sites of moderate strength, are the most active ones.
- Mashkina,Khairulina
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- Benzyllithiums bearing aldehyde carbonyl groups. A flash chemistry approach
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Reductive lithiation of benzyl halides bearing aldehyde carbonyl groups followed by reaction with subsequently added electrophiles was successfully accomplished without affecting the carbonyl groups by taking advantage of short residence times in flow microreactors.
- Nagaki, Aiichiro,Tsuchihashi, Yuta,Haraki, Suguru,Yoshida, Jun-ichi
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p. 7140 - 7145
(2015/07/01)
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- Reaction of dimethyl disulfide with thiophene catalyzed by zeolite
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Reaction of dimethyl disulfide with thiophene under the action of highly siliceous zeolite at 180-350°C and contact time 0.6-14 s resulted in formation of thioalkylation products, 2-(methylsulfanyl)- and 2,5-bis(methylsulfanyl)thiophenes and also alkylate
- Mashkina,Khairulina
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p. 217 - 220
(2015/04/14)
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- Unexpected rearrangement during the gas-phase dehalogenation approach to benzodithiophenes
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A range of halogenated methylthiophenes undergo dehalogenative condensation upon FVP over magnesium or calcium to give products including benzodithiophenes; in some cases this involves a novel rearrangement by equilibration of alkenylthienyl radicals via thiophene-fused cyclopropylmethyl intermediates. This journal is
- Aitken, R. Alan,Oyewale, Adebayo O.
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p. 19379 - 19381
(2015/04/14)
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- π-complexation in nickel-catalyzed cross-coupling reactions
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The kinetic isotope effect (KIE) is used to experimentally elucidate the first irreversible step in oxidative addition reactions of a zerovalent nickel catalyst to a set of haloarene substrates. Halogenated o-methylbenzene, dimethoxybenzene, and thiophene derivatives undergo intramolecular oxidative addition through irreversible π-complexation. Density functional theory computations at the B3LYP-D3/TZ2P-LANL2TZ(f)-LANL08d level predict η2-bound π-complexes are generally stable relative to a solvated catalyst plus free substrate and that ring-walking of the Ni(0) catalyst and intramolecular oxidative addition are facile in these intermediates.
- Sontag, S. Kyle,Bilbrey, Jenna A.,Huddleston, N. Eric,Sheppard, Gareth R.,Allen, Wesley D.,Locklin, Jason
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p. 1836 - 1841
(2014/03/21)
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- Mn(ii) acetate: An efficient and versatile oxidation catalyst for alcohols
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A homogeneous catalytic system consisting of Mn(ii) acetate (18 μmol), tert-butylhydroperoxide (2.5 mmol), acetonitrile (1.5 mL) and trifluoroacetic acid (91 μmol) was developed for efficient and selective oxidation of various alcohols (1 mmol). The system yielded good to quantitative conversions (42-100%) of various secondary alcohols, such as 2-octanol, fenchyl alcohol and borneol, to their corresponding ketones. Primary alcohols, for example 1-octanol and differently substituted benzyl alcohols, were mainly converted to their corresponding carboxylic acids. Studies with a selection of hydrocarbons, tertiary amines and a cyclic ether isochroman showed that besides alcohols, other substrates can be oxidised as well.
- Raeisaenen, Minna T.,Al-Hunaiti, Afnan,Atosuo, Elisa,Kemell, Marianna,Leskelae, Markku,Repo, Timo
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p. 2564 - 2573
(2014/07/22)
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- Iridium-catalyzed direct dehydroxylation of alcohols
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Iridium-catalyzed direct dehydroxylation of alcohols with hydrazine was developed through a combination of the oxidation of alcohols and the Wolff-Kishner reduction. This protocol is simple to perform and highly efficient for a series of primary, benzylic and allylic alcohols. Iridium-catalyzed direct dehydroxylation of alcohols with hydrazine is developed through a combination of the oxidation of alcohols and Wolff-Kishner reduction. This protocol is simple to perform and highly efficient for a series of primary alcohols, especially benzylic and allylic ones. Copyright
- Huang, Jian-Lin,Dai, Xi-Jie,Li, Chao-Jun
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supporting information
p. 6496 - 6500
(2013/11/06)
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- A C-H borylation approach to suzuki-miyaura coupling of typically unstable 2-heteroaryl and polyfluorophenyl boronates
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A method for the synthesis of biaryls and heterobiaryls from arenes and haloarenes without the intermediacy of unstable boronic acids is described. Pinacol boronate esters that are analogous to unstable boronic acids are formed in high yield by iridium-catalyzed C-H borylation of heteroarenes and fluoroarenes. These boronates are stable in the solid state or in solution and can be generated and used in situ. They couple with aryl halides in the presence of simple palladium catalysts, providing a convenient route to biaryl and heteroaryl products that have been challenging to prepare via boronic acids.
- Robbins, Daniel W.,Hartwig, John F.
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supporting information; experimental part
p. 4266 - 4269
(2012/10/08)
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- Mechanism of formation of sulphur aroma compounds from l-ascorbic acid and l-cysteine during the Maillard reaction
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The sulphur aroma compounds produced from a phosphate-buffered solution (pH 8) of l-cysteine and l-, l-[1-13C] or l-[4-13C] ascorbic acid, heated at 140 ± 2 °C for 2 h, were examined by headspace SPME in combination with GC-MS. MS data indicated that C-1 of l-ascorbic acid was not involved in the formation of sulphur aroma compounds. The sulphur aroma compounds formed by reaction of l-ascorbic acid with l-cysteine mainly contained thiophenes, thiazoles and sulphur-containing alicyclic compounds. Among these compounds, 1-butanethiol, diethyl disulphide, 5-ethyl-2-methylthiazole, cis and trans-3,5-dimethyl-1,2,4-trithiolane, thieno[2,3-b]thiophene, thieno[3,2-b]thiophene, cis and trans-3,5-diethyl-1,2,4-trithiolane, 1,2,5,6-tetrathiocane, 2-ethylthieno[2,3-b]thiophene, 2,4,6-trimethyl-1,3,5- trithiane and cyclic octaatomic sulphur (S8) were formed solely by l-cysteine degradation, and the rest by reaction of l-ascorbic acid degradation products, such as hydroxybutanedione, butanedione, acetaldehyde, acetol, pyruvaldehyde and formaldehyde with l-cysteine or its degradation products, such as H2S and NH3. A new reaction pathway from l-ascorbic acid via its degradation products was proposed.
- Yu, Ai-Nong,Tan, Zhi-Wei,Wang, Fa-Song
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experimental part
p. 1316 - 1323
(2012/06/30)
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- METHOD FOR RAPIDLY METHYLATING HETEROAROMATIC ARENE AND METHOD FOR PRODUCING TRACER FOR USE IN PET
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Provided is a method whereby a heteroaromatic ring aryl can be very rapidly methylated at a high yield. In an N-alkyl-2-pyrrolidinone, a heteroaromatic ring aryltrialkylstannan is cross-coupled with methyl iodide in the presence of a palladium complex, a phosphine ligand, a cuprous halide, a carbonic acid salt and/or an alkali metal fluoride to thereby rapidly methylate the heteroaromatic ring aryl. (Formula shows a case wherein the heteroaromatic ring aryl is a pyridyl group.)
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Page/Page column 5-6
(2011/11/06)
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- DEHYDROGENATION OF CYCLIC THIOETHERS
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There is disclosed a surprising reaction of an alkane thiol with a catalyst and heat to become dehydrogenated and form a thiophene rather than an expected desulfurization reaction to form the corresponding alkane or alkene. Moreover, there are disclosed surprising results regarding the form of a catalyst to allow a reaction of an alkane thiol to form the dehydrogenated thiophene at lower temperatures and at higher conversion percentages to allow for more efficient recovery of thiophenes to allow for recycling and reuse of thiophenes to hydrogenate to form alkane thiols. Further still, there is disclosed a set of reaction conditions and catalyst presentation that allows for recovery of usable diatomic hydrogen gas from a dehydrogenation reaction of substituted or unsubstituted cyclic thioethers to substituted or unsubstituted thiophene.
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Page/Page column 25
(2011/05/11)
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- A simple and efficient hydrogenation of benzyl alcohols to methylene compounds using triethylsilane and a palladium catalyst
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Hydrogenolysis of benzyl alcohols using triethylsilane (Et3SiH) and a catalytic amount of palladium(II) chloride (PdCl2) is described. The reaction takes place under mild conditions affording high yields of the corresponding methylene compounds in short reaction times.
- Mirza-Aghayan, Maryam,Boukherroub, Rabah,Rahimifard, Mahshid
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experimental part
p. 5930 - 5932
(2010/01/18)
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- METHOD OF RAPID METHYLATION, KIT FOR PREPARING PET TRACER AND METHOD OF PRODUCING PET TRACER
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It is intended to provide a method of rapid methylation of an aromatic compound or an alkenyl compound, which is capable of obtaining an aromatic compound or an alkenyl compound labeled with a methyl group or a fluoromethyl group under a mild condition rapidly in high yield using an organic boron compound whose toxicity is not so high as a substrate; a kit for preparing a PET tracer to be used in the same, and a method of producing a PET tracer using the same. In an aprotic polar solvent, methyl iodide or X-CH2F (wherein X is a functional group which can be easily released as an anion), an organic boron compound in which an aromatic ring or an alkenyl group is attached to boron are subjected to cross-coupling in the presence of a palladium(0) complex, a phosphine ligand, and a base.
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Page/Page column 9
(2009/07/10)
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- Pd0-mediated rapid coupling between methyl iodide and heteroarylstannanes: an efficient and general method for the incorporation of a positron-emitting11C radionuclide into heteroaromatic frameworks
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The Pd0-mediated rapid trapping of methyl iodide with an excess amount of a heteroaryl-substituted tributylstannane has been investigated with the aim of incorporating a shortlived 11C-labelled methyl group into the heteroaromatic carbon frameworks of important organic compounds, such as drugs with various heteroaromatic structures, in order to execute a positron emission tomography (PET) study of vital systems. The reaction was first performed by using our previously developed CH3I/stannane/[Pd 2(dba)3]/ P(o-CH3C6H 4)3/CuCl/K2CO3 (1:40:0.5:2:2:2) system in DMF at 60°C for 5 min (conditions A), however, the reaction gave low yields for various heteroaromatic compounds. Increasing the amount of phosphine ligand (condi tions B) led to a significant improvement in the yield, but the conditions were still not suitable for a range of basic heteroaromatic structures. Use of the CuBr/CsF system (conditions C) also provided a result similar to that obtained under conditions B with an increased amount of the phosphine. Thus, pyridine and related heteroaromatic compounds remained less reactive substrates. The problem was overcome by replacing the DMF solvent with N-methyl-2-pyrolidinone (NMP). The reaction in NMP at 60-100°C for 5 min using a CH3I/stannane/[Pd2-(dba)3]/P(o-CH 3C6H4)3/CuBr/CsF (1:40:0.5:16:2:5) combination (conditions D) gave the methylated products in yields of more than 80% (based on the reaction of CH3I) for all of the heteroaromatic compounds listed in this study. Thus, the combined use of NMP and an increased amount of phosphine is important for promoting the reaction efficiently. The use of this general approach to rapid methylation has been well demonstrated by the synthesis of the PET tracers 2- and 3-[11C]methylpyridines by using [Pd2(dba)3]/P(o-CH3C6H 4)3/CuBr/CsF (1:16:2:5) in NMP at 60°C for 5 min, which gives the desired products in HPLC analytical yields of 88 and 91%, respectively.
- Suzuki, Masaaki,Sumi, Kengo,Koyama, Hiroko,Siqin,Hosoya, Takamitsu,Takashima-Hirano, Misato,Doi, Hisashi
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experimental part
p. 12489 - 12495
(2010/06/11)
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- Palladium(0)-mediated rapid methylation and fluoromethylation on carbon frameworks by reacting methyl and fluoromethyl iodide with aryl and alkenyl boronic acid esters: Useful for the synthesis of [11C]CH 3-C-and [18F]FCH2-C-containing PET tracers (PET = positron emission tomography)
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The rapid methylation and fluoromethylation on aryl and alkenyl carbon frameworks by reacting methyl and fluoromethyl iodide with aryl and alkenyl boronates have been studied with the focus on the realization of the synthesis of [11C]CH3- and [18F]FCH2-labeled positron emission tomography (PET) tracers. The coupling of methyl iodide and pinacol phenylboronate (40 equiv) is accomplished in > 91% yield within 5 min at 60 °C under the conditions of [Pd2(dba)3]/P(o- CH3C6H4)3/K2CO 3 (0.5:2:2; dba = di-benzylideneacetone) in DMF. The reaction shows a high generality and is applicable to various types of aryl and alkenyl boronates, giving the corresponding methylated derivatives in high yields (80-99). This reaction is also useful for the rapid incorporation of the fluoromethyl group. Thus, this boron protocol provides a firm chemical basis for the synthesis of 11C- and 18F-incorporated PET tracers and can be used as a complementary method for [11C]methylation together with our previous and ongoing processes using organotributylstannanes.
- Doi, Hisashi,Ban, Ikuya,Nonoyama, Akihito,Sumi, Kengo,Kuang, Chunxiang,Hosoya, Takamitsu,Tsukada, Hideo,Suzuki, Masaaki
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experimental part
p. 4165 - 4171
(2009/12/01)
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- Catalytic transformations of alkylthiophenes
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The transformations of alkylthiophenes in the presence of amorphous aluminosilicate and decationated zeolite HNaY were studied. Substituted thiophenes with R = 2- and 3-Me, 2-Et, and 2-iso-Pr undergo dealkylation to thiophene with close rates, migration of the alkyl group from the 9α- to the β-position of the thiophene ring (or in the opposite direction with an elevated rate), and decomposition with H2S elimination. The dealkylation rate of 2-substituted thiophenes with a branched-chain radical (R = iso-Pr, terf-Bu) is much higher and the elimination rate with this radical is lower than those for normal-chain radicals; the isomerization step is virtually absent. Di-, tri-, and tetrasubstituted thiophenes with R = Et and iso-Pr undergo stepwise dealkylation, which is facilitated by an increase in the degree of substitution on the thiophene ring. Thiophene and its lower homologues can be obtained by the transformation of a mixture of high-molecular thiophenes. Copyright
- Mashkina,Chernov
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p. 209 - 215
(2007/10/03)
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- Synthesis and biological evaluation of thiophene [3,2-b] pyrrole derivatives as potential anti-inflammatory agents
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A series of thiophene [3,2-b] pyrrole derivatives were synthesized and evaluated their abilities to inhibit anti-inflammatory activity. In this series, substituent effects at the N-1, 2 and 5 positions of thiophene [3,2-b] pyrrole were examined. The results obtained are compared to those previously reported anti-inflammatory drugs like Tenidap sodium, Diclofenac sodium and Piroxicam. The results indicated the critical role of the group linked in the N-1 position and 2, 5 positions of thiophene [3,2-b] pyrrole with different functional groups.
- Rajender Kumar,Raju,Satish Goud,Sailaja,Sarma,Om Reddy,Prem Kumar,Krishna Reddy,Suresh,Hegde, Pragathi
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p. 1221 - 1230
(2007/10/03)
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- Synthesis of C3-symmetric nano-sized polyaromatic compounds by trimerization and Suzuki-Miyaura cross-coupling reactions
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Various C3-symmetric molecules were prepared by trimerization of acetyl aromatic compounds and subsequently coupled with various boronic acids under Pd0 catalysis conditions to generate oligoaryl/-heteroaryl C3-symmetric molecules. Several furan- and thiophene-containing star-shaped molecules were prepared by the use of Suzuki-Miyaura cross-coupling as a key step. Structural and conformational details were explored by semi-empirical molecular orbital theory using the AM1 method. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Kotha, Sambasivarao,Kashinath, Dhurke,Lahiri, Kakali,Sunoj, Raghavan B.
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p. 4003 - 4013
(2007/10/03)
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- Influence of the texture of chromia catalysts on their activity in synthesis of 2-methylthiophene
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The texture of Cr2O3-K2O/Al 2O3 catalysts containing oxides of rare earth elements (REE) was studied. The catalysts are used for the synthesis of 2-methylthiophene by the reaction of H2S with n-pentane or piperilene. The heterocyclization of n-pentane is a consecutive reaction involving a step of dehydrogenation of initial hydrocarbon. At this step the texture of the catalyst affects the yield of 2-methylthiophene. The yield of 2-methylthiophene obtained from piperilene and H2S is independent of the catalyst texture.
- Ryashentseva,Brueva
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p. 1694 - 1697
(2007/10/03)
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- Identification of intermediates in the reaction of 2-thenyl halides with magnesium
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The reaction of 2-thenyl chloride with magnesium was shown by the ESR method to proceed via the intermediate formation of radicals and radical ion pairs, whereas similar reactions of 2-thenyl bromide and iodide occur through the formation of free radicals only.
- Egorov,Kuznetsova,Anisimov
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p. 1544 - 1547
(2007/10/03)
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- Synthesis of 2-methylthiophene by catalytic dehydrocyclization of 1,3-pentadiene with hydrogen sulfide
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A procedure has been developed for preparation of highly pure 2-methylthiophene by dehydrocyclization of 1,3-pentadiene with hydrogen sulfide over aluminum-chromiun-potassium catalyst, followed by isolation of the product by high-performance rectification.
- Sharipova,Nasyrov,Mozgovaya,Sharipov
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p. 1445 - 1447
(2007/10/03)
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- Direct Carbonylation of Benzyl Alcohol and Its Analogs Catalyzed by Palladium and HI in Aqueous Systems and Mechanistic Studies
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Carbonylation of benzyl alcohol, benzyl formate, dibenzyl ether, and benzyl phenylacetate catalyzed by palladium complexes and promoted by hydrogen iodide gives phenylacetic acid in moderate to excellent yields in aqueous systems. Application of the carbonylation process to other arylmethanol analogs provides convenient means to prepare 2-naphthaleneacetic acid, 3-isochromanone, 1,4-benzenediacetic acid, and o-hydroxybenzeneacetic acid. A mechanism for the catalytic reaction is proposed, which involves (1) formation of benzyl iodide by the reaction of benzyl alcohol with HI in situ, (2) oxidative addition of benzyl iodide to palladium(0) to form a benzylpalladium iodide species. (3) CO insertion into the Pd-benzyl bond to form a (phenylacetyl)palladium iodide species. (4) reductive elimination of phenylacetyl iodide, and (5) its hydrolysis into phenylacetic acid. Evidence supporting the mechanism was obtained by examining the properties of benzyl- and (phenylacetyl)palladium iodide and chloride complexes. Formation of benzyl(carbonyl)palladium species and migratory insertion of the benzyl group to CO was confirmed by means of NMR at low temperature under high pressure.
- Lin, Yong-Shou,Yamamoto, Akio
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p. 723 - 734
(2007/10/03)
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- Rapid coupling of methyl iodide with aryltributylstannanes mediated by palladium(0) complexes: A general protocol for the synthesis of 11CH3-labeled PET tracers
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The reaction of methyl iodide and (excess) aryltributylstannane to give a methylarene has been studied with the focus on the realization of rapid coupling for incorporation of short-lived radionuclides into bioactive organic compounds. The coupling of methyl iodide with tributylphenylstannane (40 equiv) is accomplished in >90% yield within 5 min at 60°C with a tri-o-tolylphosphine-bound, coordinatively unsaturated Pd(o) complex together with a Cu(I) salt and K2CO3 in DMF. This protocol is applicable to a variety of homo- and heteroaromatic tin compounds, to give the corresponding methylated derivatives. The effects of the tri-o-tolylphosphine ligand, a Cu(I) salt, and DMF are discussed. This new protocol provides a firm chemical basis for the synthesis of 11CH3-incorporated PET tracers.
- Suzuki, Masaaki,Doi, Hisashi,Bjoerkman, Margareta,Andersson, Yvonne,Langstroem, Bengt,Watanabe, Yasuyoshi,Noyori, Ryoji
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p. 2039 - 2042
(2007/10/03)
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- Pyrolytic chemistry of thenyl benzoates
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Flash vacuum pyrolysis of 2- and 3-thenyl benzoates (4 and 5, respectively) at temperatures in the range 550-750°C and ca. 10-2 torr gave several radical-derived products. The mechanism of formation of these pyrolysis products is proposed to involve 2-, 3-thenyl and phenyl radicals.
- Chen, Ping-Shu,Chou, Chin-Hsing
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p. 13615 - 13622
(2007/10/03)
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- Competitive reactivities of vinylthiyl radicals thermally generated from haloethylenes and hydrogen sulfide
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Acetylene and its derivatives have been used for the first time as "traps" for vinylthiyl radicals generated in situ from hydrogen sulfide and haloethylenes in gas-phase processes. The competitive reactivity of the vinylthiyl radicals has been studied at 500-570 °C in the presence of two chemical "traps." The efficiency of chemical "traps" for the vinylthiyl radicals decreases in the following sequence: HC≡CPh > HC≡CH > MeC≡CH > CH2=CHCl. Acetylene is a more efficient "trap" for the vinylthiyl radicals than 1,2-dichloroethylene, from which they have been generated. The β-phenylvinylthiyl radicals generated during cothermolysis of halostyrene-hydrogen sulfide-acetylene component ternary systems undergo first of all intramolecular ring closure to give benzothiophene, which is a thermodynamically favorable system; the reaction of these radicals with acetylene and its derivatives occurs much more slowly than heterocyclization. Phenylacetylene is a more efficient "trap" than acetylene. α-Phenylvinylthiyl radicals mostly react with acetylene to yield 2-phenylthiophene.
- Deryagina,Sukhomazova,Levanova
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p. 662 - 666
(2007/10/03)
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- HIGH-TEMPERATURE ORGANIC SYNTHESIS XXXV. THERMAL REACTIONS OF DI(1-PROPENYL) SULFIDE
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The thermolysis of dipropenyl sulfide in a flow-type system in an atmosphere of nitrogen at 450-540 deg C leads to propenethiol, thiophene, methylthiophenes, and 2-ethylthiophene.The formation of the thiophene derivatives results from intramolecular radical cyclization of the initial sulfide.Dimethyl selenide (5-10 mole percent) substantially accelerates the thermolysis of dipropenyl sulfide, and the yield of 2-ethylthiophene at 450-480 deg C is increased appreciably.The high-temperature reactions of di(1-propenyl) sulfide with 2-halogenothiophenes and acetylene confirm that the propenethiol and thiophene derivatives are formed in parallel during the thermolysis of dipropenyl sulfide.
- Ostroukhova, L. A.,Deryagina, E. N.,Korchevin, N. A.,Musorin, G. K.,Amosova, S. V.,Voronkov, M. G.
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p. 301 - 305
(2007/10/02)
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- Volatile Products Formed from L-Cysteine and Propanal Thermally Treated in Triglyceride-Water Systems
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Volatile compounds formed from model systems of equimolar amounts of L-cysteine and propanal reacted at 110 deg C for 3 h in triglyceride, deionized and distilled water, or their mixtures were investigated.The volatiles were isolated by ether extraction of vacuum steam-distillated of reaction mixtures and analyzed by gas chromatography and coupled gas chromatography-mass spectrometry.Qualitative and quantitative differences in volatiles formed in the systems were observed.The amounts of total volatiles were highly varied according to the composition of the reaction medium. 2-Ethylthiazolidine was the most predominant in the triglyceride sstem. 2-Methyl-2-pentenal was a sevcondary dominating product in the triglyceride system and the most predominant in the triglyceride-water and water systems.The amounts of other volatile compounds including a novel compound, 2-ethylthiazolidinthiazolidine (I), were also changed according to the systems.The highest production of I was observed in the triglyceride-water (75:25) system.
- Okumura, Joji
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p. 1537 - 1545
(2007/10/02)
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- HETEROCYCLIZING PROPERTIES OF FERRISILICATE IN THE REACTION OF n-PENTANE WITH HYDROGEN SULFIDE
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Unlike the iron-modified pentasil, the ferrisilicate has high heterocyclizing activity in the formation of 2-methylthiophene from hydrogen sulfide and n-pentane.During the reaction and the subsequent regenerations a considerable proportion of iron ions leaves the ferrisilicate lattice.The heterocyclizing activity is probably related to the formation of a highly dispersed Fe sulfide phase in the zeolite channels.
- Ryashentseva, M. A.,Belanova, E. P.,Minachev, Kh. M.,Kucherov, A. V.
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p. 1551 - 1555
(2007/10/02)
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- Equilibrium studies of thiophene exchange in (η-thiophene)Ru(η-C5H5)+: A model for thiophene adsorption on hydrodesulfurization catalysts
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Equilibrium constants (K′) for the displacement of the π- (i.e., η5-) thiophene (T) ligand in CpRu(T)+ by methyl-substituted thiophenes (Th′), CpRu(T)+ + Th′ ? CpRu(Th′)+ + T, increase as the number of methyl groups in Th′ increases: T (1) 2T (35) 2T (50) 3T(200) 3T (300) 4T (1300). The K′ values increase by a factor of approximately 6 for each methyl in the thiophene (Th′). That thiophenes also adsorb to a Co-Mo/Al2O3 hydrodesulfurization (HDS) catalyst more strongly as the number of methyl groups in the thiophene increases suggests that they are also π-bonded to the catalyst surface. The results suggest that trends in rates of deuterium exchange and hydrodesulfurization on HDS catalysts for a series of methyl-substituted thiophenes are determined by their relative strengths of adsorption to the catalyst surface.
- Hachgenci,Angelici
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- REACTION OF FURAN COMPOUNDS WITH HYDROGEN SULFIDE AND ASPECTS OF ITS APPLICATION
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The conversion of α-methylfuran, di-, and polyalkylfurans, and ethers, esters, ketones, and other derivatives of the furan series to the corresponding substituted thiophenes was realized under acid-catalysis conditions.
- Kharchenko, V. G.,Gubina, T. I.,Voronin, S. P.,Markushina, I. A.
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p. 1170 - 1173
(2007/10/02)
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- Cleavage of Furan-2-yl, 2-Thienyl-, Benzofuran-2-yl-, and Benzothiophen-2-yl-methyl(trimethyl)silanes (RCH2SiMe3) by Methanolic Sodium Methoxide; Acidities of the Corresponding RCH3 Species
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Rates of cleavage of RCH2SiMe3 by 2.00M-NaOMe in MeOH or MeOD at 50 deg C have been determined for R = furan-2-yl, 2-thienyl, benzofuran-2-yl, and benzothiophen-2-yl; the values of 1E5ks in MeOH and (in parentheses) in MeOD, where ks is the specific second order rate constant, are, respectively: 0.070 (0.167), 0.26 (0.52), 165 (310), and 70 (130) dm3 mol-1 s-1.The values of the ratios of ks in MeOH to hat in MeOD are in the range 0.42-0.54, consistent with rate-determining separation of the carbanion RCH2-. s is 1.57 (1.55), the ratio is 1.01, consistent with electrophilic assistance by proton transfer from the solvent to the separating carbon centre.> The results are discussed in the light of the deprotonation energies calculated (STO-3G) for the corresponding carbon acids RCH3, and approximate pKa values are derived for the latter, viz. (R =) furan-2-yl, 40.6; 2-thienyl, 39.7; benzofuran-2-yl, 35.2; benzothiophen-2-yl, 35.8.
- Dembech, Pasquale,Seconi, Giancarlo,Eaborn, Colin,Rodriguez, Juan A.,Stamper, John G.
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p. 197 - 198
(2007/10/02)
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- Cleavage of 5-Nitro-2-(trimethylsilylmethyl)thiophene by Methanolic Sodium Methoxide. U.V. Spectroscopic and Solvent Isotope Effect Evidence for Generation of the Anion (1-)
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The reaction of 5-nitro-2-(trimethylsilylmethyl)thiophene with NaOMe-MeOH involves generation of the observable anion (1-) with a solvent isotope effect k(MeOH)/k(MeOD) of 0.5, followed by protonation of the anion with a solvent isotope effect of 10; the results confirm that cleavages of RSiMe3 compounds by NaOMe-MeOH involve separation of the anions R(1-), and that the isotope effect in the reaction of R(1-) with MeOH depends greatly on the degree of conjugative delocalization of the negative charge, not just on the acidity of RH.
- Dembech, Pasquale,Eaborn, Colin,Seconi, Giancarlo
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p. 1289 - 1290
(2007/10/02)
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- Reactions of Thiophene and Alkylthiophenes in Glow Discharge
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The glow discharge reaction of thiophene is shown to produce thioketene and carbon monosulfide along with other gaseous products.The dominant liquid product is ethynylthiophene.Methylthiophenes and especially dimethylthiophenes produce benzene as one of the major liquid products.
- Skramstad, Jan,Chaudhry, Mohammed Shoaib,Garvang, Arne
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p. 509 - 512
(2007/10/02)
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