- PYROLYSIS OF SILICON-CONTAINING CYCLIC POLYSULPHIDES
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Thermal decomposition of silicon-containing monocyclic polysulphides (1-methyl-3-trimethylsilyl-2,5-dithiacyclopentane (I), 1,4-bis(trimethylsilyl)-2,3,6,7-tetrathiacyclooctane (II) and 1-trimethylsilyl-2,3,4,5,6-pentathiacycloheptane (III)) has been stud
- Chernyshev, E. A.,Kuz'min, O. V.,Lebedev, A. V.,Zaikin, V. G.,Mikaya, A. I.
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- Self-assembly of catalytically active supramolecular coordination compounds within metal?organic frameworks
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Supramolecular coordination compounds (SCCs) represent the power of coordination chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesized in solution, with isolated fully coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal?organic frameworks (MOFs) show unique features to act as chemical nanoreactors for the in situ synthesis and stabilization of otherwise not accessible functional species. Here, we present the self-assembly of PdII SCCs within the confined space of a pre-formed MOF (SCCs@MOF) and its post-assembly metalation to give a PdII?AuIII supramolecular assembly, crystallography underpinned. These SCCs@MOFs catalyze the coupling of boronic acids and/or alkynes, representative multi-site metal-catalyzed reactions in which traditional SCCs tend to decompose, and retain their structural integrity as a consequence of the synergetic hybridization between SCCs and MOFs. These results open new avenues in both the synthesis of novel SCCs and their use in heterogeneous metal-based supramolecular catalysis.
- Adam, Rosa,Mon, Marta,Greco, Rossella,Kalinke, Lucas H.G.,Vidal-Moya, Alejandro,Fernandez, Antonio,Winpenny, Richard E.P.,Domenech-Carbo, Antonio,Leyva-Perez, Antonio,Armentano, Donatella,Pardo, Emilio,Ferrando-Soria, Jesus
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supporting information
p. 10350 - 10360
(2019/08/20)
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- Self-Assembly of Catalytically Active Supramolecular Coordination Compounds within Metal-Organic Frameworks
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Supramolecular coordination compounds (SCCs) represent the power of coordination chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesized in solution, with isolated fully coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-organic frameworks (MOFs) show unique features to act as chemical nanoreactors for the in situ synthesis and stabilization of otherwise not accessible functional species. Here, we present the self-assembly of PdII SCCs within the confined space of a pre-formed MOF (SCCs?MOF) and its post-assembly metalation to give a PdII-AuIII supramolecular assembly, crystallography underpinned. These SCCs?MOFs catalyze the coupling of boronic acids and/or alkynes, representative multi-site metal-catalyzed reactions in which traditional SCCs tend to decompose, and retain their structural integrity as a consequence of the synergetic hybridization between SCCs and MOFs. These results open new avenues in both the synthesis of novel SCCs and their use in heterogeneous metal-based supramolecular catalysis.
- Adam, Rosa,Mon, Marta,Greco, Rossella,Kalinke, Lucas H. G.,Vidal-Moya, Alejandro,Fernandez, Antonio,Winpenny, Richard E. P.,Doménech-Carbó, Antonio,Leyva-Pérez, Antonio,Armentano, Donatella,Pardo, Emilio,Ferrando-Soria, Jesús
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supporting information
p. 10350 - 10360
(2019/08/27)
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- Photocatalytic degradation of benzothiophene by a novel photocatalyst, removal of decomposition fragments by MCM-41 sorbent
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In this study, a catalyst was synthesized by introduction of ZnO onto the surface of FSM-16 catalyst support (ZnO/FSM-16). Impregnation of catalyst support by ZnO proceeded through reacting of FSM-16 nanoparticles with Zn(CH3COO)2 solution followed by calcination of the product. The synthesized photocatalyst was then identified by different methods, and the optical property of the photocatalyst was studied by the DRS method. The results showed that after deposition of photocatalyst on FSM-16 support, the photocatalyst band gap was shifted to the visible region. The photoluminescence studies revealed lower recombination of electron–holes of the photocatalyst after immobilization on FSM-16. The influence of different variables on the photocatalytic performance of the samples was studied. Under optimized conditions, the high degradation efficiency of 97% was obtained by ZnO/FSM-16. The compounds produced from degradation of benzothiophene were recognized by the GC–MS method, and the products containing sulfur were properly adsorbed by MCM-41 sorbent. The photocatalyst showed high regeneration capability, and its activity was mostly preserved after six regeneration cycles.
- Hosseini, Asma,Faghihian, Hossein
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p. 2383 - 2401
(2019/01/29)
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- Pd/C-catalyzed direct formylation of aromatic iodides to aryl aldehydes using carbon dioxide as a C1 resource
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Pd/C-catalyzed direct formylation of aromatic iodides to aryl aldehydes using CO2 as a C1 resource was realized for the first time in the presence of hydrosilanes and base DBU under mild conditions, giving a series of aldehydes in good yields. The Royal Society of Chemistry 2014.
- Yu, Bo,Zhao, Yanfei,Zhang, Hongye,Xu, Jilei,Hao, Leiduan,Gao, Xiang,Liu, Zhimin
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supporting information
p. 2330 - 2333
(2014/03/21)
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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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- Leaving group dependence of the rates of halogen-magnesium exchange reactions
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Relative reactivities and absolute rate constants of the reactions of haloarenes with i-PrMgCl?LiCl were investigated in THF at 0 °C. The rate of the halogen-magnesium exchange decreases in the series ArI > ArBr > ArCl (relative reactivities: 1011:106:1). Preliminary experiments show that the p-tolylsulfinyl group is exchanged slightly faster than iodide, while a tosyl group is exchanged at least 104 times more slowly than a bromide.
- Shi, Lei,Chu, Yuanyuan,Knochel, Paul,Mayr, Herbert
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supporting information; experimental part
p. 2602 - 2605
(2012/08/08)
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- Palladium catalyzed-dehalogenation of aryl chlorides and bromides using phosphite ligands
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The catalytic system based on Pd-phosphite for the dehalogenation reactions of aryl chlorides and bromides is described. The Pd-phosphite catalyst effectively promoted the dehalogenation of aryl halides to give dehalogenated products in moderate to excellent yields. The aryl chlorides required strong bases such as NaOtBu for this transformation, whereas the aryl bromides were dehalogenated in the presence of weak bases such as Cs2CO3. This catalytic system exhibited tolerance to functional groups such as methoxy, amine, hydroxyl, ether, amide, benzyl and ketone groups. It also demonstrated chemoselectivity in that bromochlorobenzene was converted only to chlorobenzene.
- Moon, Jeongju,Lee, Sunwoo
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scheme or table
p. 473 - 477
(2009/04/14)
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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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- High-temperature synthesis of thiophene from bis(2-chloroethyl) sulfide
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Gas-phase reaction of bis(2-chloroethyl) sulfide (Yperite) with acetylene at 550-700°C leads to formation of thiophene in 45% yield, the conversion of the initial sulfide being complete. The yield of thiophene reaches 63-68% in the thermolysis of a mixture of acetylene, bis(2-chloroethyl) sulfide, and lower organic disulfides.
- Voronkov,Levanova,Sukhomazova,Russavskaya,Deryagina,Korchevin
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p. 891 - 893
(2007/10/03)
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- The thermal decomposition of 5-membered rings: A laser pyrolysis study
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The mechanisms of pyrolysis of cyclopentadiene, furan, pyrrole and thiophene have been investigated using a combination of IR laser powered homogeneous pyrolysis, chemical and physical trapping of radical intermediates, and use of precursors specifically designed to generate selected radical intermediates. The results confirm the central role played by free radicals in the cases of cyclopentadiene and thiophene, and the dominant step of 1,2-H shifts in the cases of furan and pyrrole. The experimental results may be interpreted according to the high level ab initio calculations recently reported in the literature.
- Hore, Nathan R.,Russell, Douglas K.
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p. 606 - 613
(2007/10/03)
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- New chemical synthesis of functionalized arylzinc compounds from aromatic or thienyl bromides under mild conditions using a simple cobalt catalyst and zinc dust
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A new chemical method for the preparation of arylzinc intermediates is described in acetonitrile, on the basis of the activation of aryl bromides by low-valent cobalt species arising from the reduction of cobalt halide by zinc dust. This procedure allows for the synthesis of a variety of functionalized aryl- and thienylzinc species in good to excellent yields. The versatility and the simplicity of that original method represent an alternative to most known procedures.
- Fillon, Hyacinthe,Gosmini, Corinne,Perichon, Jacques
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p. 3867 - 3870
(2007/10/03)
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- Novel synthesis of arylboronic acids by electroreduction of aromatic halides in the presence of trialkyl borates
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A novel preparation of aryl and heteroarylboronic acids by an electrochemical coupling reaction is described. It is based on the reductive coupling between aromatic or heteroaromatic halides and a trialkyl borate. The reactions are carried out in DMF or THF with the use of sacrificial aluminium or magnesium anodes in a single-compartment cell. Arylboronic acids are obtained with moderate to good selectivities and isolated yields.
- Laza, Carine,Dunach, Elisabet,Serein-Spirau, Francoise,Moreau, Joel J. E.,Vellutini, Luc
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p. 373 - 375
(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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- Initiation of thermal reactions of sulfur compounds by dialkyl selenides
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The use of diethyl selenide (20-40 mol %) as initiator in the gas-phase synthesis of thiophene from diethyl disulfide and acetylene increases the selectivity of the process and the yield of thiophene from 40 to 92%. As a result, this reaction becomes the most efficient preparative method for the synthesis of thiophene and also of selenophene which is formed in up to 70% yield. The complete conversion of both sulfur-and selenium-containing reagents is attained. Due to much different boiling points, thiophene and selenophene can readily be separated by rectification of the reaction mixture. Dialkyl selenides also initiate other thermal reactions of hydrogen sulfide and organic sulfides.
- Deryagina,Sukhomazova,Levanova,Shilkina,Korchevin
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p. 359 - 363
(2007/10/03)
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- Reductive coupling of halogenothiophenes and halogenothiazoles catalysed by PdII in a basic alcohol medium
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A catalytic reductive coupling method has been developed whereby 2- and 3-bromo- and 2-iodothiophenes, 2-bromothiazole and 2-bromofuran are converted into their corresponding bithiophene, bithiazole and bifuran derivatives. The use of a basic alcohol medium favours the reductive coupling pathway over the hydrodehalogenation pathway, which is generally more facile when other reducing agents are used. The catalytic mechanisms are discussed. The syntheses and characterization of the proposed intermediate complexes, trans-[PdBr(C4H3S-C)(PPh3)2] 1, trans-[PdI(C4H3S-C)(PPh3)2] 2 and trans-(N,P)-[{PdBr(μ-C3H2NS-C2,N)(PPh 3)}2]·1/2CHCl3 3 support the proposed mechanism and the catalytic results. Single-crystal X-ray crystallographic structure determinations of 2 and 3 were carried out.
- Xie, Yang,Tan, Geok Kheng,Yan, Yaw Kai,Vittal, Jagadese J.,Ng, Siu Choon,Hor, T. S. Andy
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p. 773 - 779
(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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- 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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- Electrochemical reduction of mono- and dihalothiophenes at carbon cathodes in dimethylformamide. First example of an electrolytically induced halogen dance
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Cyclic voltammetry and controlled-potential electrolysis have been employed to probe the electrochemical reduction of a number of mono- and dihalothiophenes at carbon cathodes in dimethylformamide containing tetramethylammonium perchlorate. Reduction of 2
- Mubarak, Mohammad S.,Peters, Dennis G.
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p. 8074 - 8078
(2007/10/03)
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- Thiyl radicals in gas-phase thermolysis of xanthic acid esters
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Gas-phase thermolysis of xanthic acid esters and their reaction with acetylene at 250-600°C have been studied for the first time. The direction of the thermolysis is determined by the nature of the substituents at the oxygen and sulfur atoms. The main products of the thermolysis are gaseous hydrocarbons, carbon monoxide and hydrogen sulfide. The yields of liquid products of the thermolysis and of the reactions with acetylene are 4-46 %. The role of thiyl radicals in thiophene molecule formation and reaction routes to carbon disulfide, dithiocarbonates, and stilbene are discussed.
- Deryagina,Korchevin,Russavskaya,Sukhomazova,Levanova
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p. 140 - 143
(2007/10/03)
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- USE OF "DISULPHIDE OIL" IN THE HIGH-TEMPERATURE SYNTHESIS OF HETEROCYCLIC COMPOUNDS
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The pyrolysis of dimethyl and diethyl disulphides and "disulphide oil" ( a waste product of oil refining) was carried out at 580-610 deg C.On the basis of the gas-phase reaction of "disulphide oil" with the chlorobenzene-acetylene system or 2-chlorothiophene-acetylene system, new methods have been developed for the simultaneous production of thiophene and benzothiophene or thiophene and thienothiophene in high yields.The mechanism of the reactions studied are discussed.
- Deryagina, E. N.,Korchevin, N. A.,Sukhomazova, E. N.,Russavskaya, N. V.,Levanova, Ye. P.
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p. 457 - 462
(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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- THERMAL TRANSFORMATIONS OF ALLYL 2-THIENYL SULFIDE AND SELENIDE
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In the gas phase at 350-410 deg C allyl 2-thienyl sulfide is converted to thiophene-2-thiol, di(2-thienyl) sulfide, and 2-methylthienothiophene.In the presence of acetylene thienothiophene is formed in addition to these products.Allyl 2-thienyl selenide is converted quantitatively to 2,3-dihydro-2-methylselenophenothiophene during fractional distillation in vacuo.Thiophene, di(2-thienyl) selenide, di(2-thienyl) diselenide, thiophene-2-selenol, and 2-methylselenophenothiophene are formed in addition to these compounds in the thermolysis ofallyl thienyl selenide in the gas phase.In the presence of acetylene the thermal decomposition of allyl thienyl selenide is accompanied by the formation of selenophene.
- Korchevin, N. A.,Sukhomazova, E. N.,Russavskaya, N. V.,Turchaninova, L. P.,Sigalov, M. V.,et al.
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p. 1049 - 1052
(2007/10/02)
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- A novel and convenient method for palladium-catalysed alkoxycarbonylation of aryl and vinyl halides using HCO2R/NaOR system
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Aryl iodides, vinyl bromides and tricarbonyl(chloroarene)chromium complexes react under mild conditions with sodium alkoxides and alkyl formates as source of carbon monoxide in the presence of dichlorobis(triphenylphosphine)-palladium as catalyst to give the corresponding carboxylic esters in high yields.
- Carpentier,Castanet,Brocard,Mortreux,Petit
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p. 4705 - 4708
(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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- FORMATION OF THIENOTHIOPHENES IN THE HIGH TEMPERATURE REACTION OF 2-CHLOROTHIOPHENE WITH COMPOUNDS CONTAINING THE C2H5S GROUP
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The high temperature gas-phase reaction of 2-chlorothiophene with a mixture of diethyl disulfide and diethyl trisulfide constitutes a simple one-step synthesis of a 4:1 mixture of thioeno- and thieno-thiophenes.Their total yield depends on the nature of the donor of the ethylthio group.
- Korchevin, N. A.,Sukhomoazova, E. N.,Turchaninova, L. P.,Efremova, G. G.,Kalinina, N. A.,et al
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p. 857 - 860
(2007/10/02)
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- TERTIARY BUTYLATION OF FIVE MEMBERED HETEROCYCLES. A UPS STUDY
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The reaction of 2-chloromercuryfuran and t-butylbromide was studied by UV photoelectron spectroscopy.During the reaction the formation of t-butylfuran, 2,5-di-t-butylfuran, t-butylchloride, isobutylene and furan were found.In accordance with the experimental observations a novel reaction mechanism has been proposed.The first fast and the second slow step of the reaction has been interpreted.The corresponding thiophene derivative gave similar results.
- Nyulaszi, L.,Gyuricza, A.,Veszpremi, T.
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p. 5955 - 5960
(2007/10/02)
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- THERMAL HYDROTHIOLYSIS OF DI(2-THIENYL)SULFIDE IN THE GASEOUS AND LIQUID PHASE
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At 500-600 deg C, di(2-thienyl)sulfide is converted to thiophene, thiophene thiols, dithienyls, and dithienothiophenes, and isomerized to 2,3-dithienylsulfide.Hydrogen sulfide accelerates these reactions significantly.In the liquid phase the thermal conversion of di(2-thienyl)sulfide takes place only with the participation of elemental sulfur or in the system sulfur-hydrogen sulfide.Thiophene and diethienothiophenes are not formed in this case, while isomerization occurs to a large degree.The observed thermal conversions of di(2-thienyl)sulfide are based on the addition of thiyl radicals to the double bonds of the thiophene ring and to the sulfide sulfur atom.
- Voronkov, M. G.,Deryagina, E. N.,Papernaya, L. K.,Sukhomazova, E. N.,Korchevin, N. A.,Efremova, G. G.
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p. 1301 - 1306
(2007/10/02)
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- HIGH-TEMPERATURE ORGANIC SYNTHESIS. XXVII. REACTIONS OF ALKANETHIONES WITH THE CHLORINE DERIVATIVES OF BENZENE, THIOPHENE, AND NAPHTHALENE
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Alkanethiols react effectively with chlorobenzene, its derivatives, 1-chloronaphthalene, and 2-chlorothiophene at 600-660 deg C with the preferential formation of the corresponding aromatic or heteroatomic thiols.Ethanethiol is most reactive.When it is used instead of hydrogen sulfide in reactions with chlorobenzene or its 4-substituted derivatives, the yield of the aromatic thiols, from which the phenylthiyl radicals are generated with greater difficulty, increases more sharply than the yield of the thiophenols, which generate the more stable 4-XC6H4S radicals.The side products of the reactions are the corresponding diaryl sulfides, thiophene, benzothiophene, and toluene.
- Voronkov, M. G.,Deryagina, E. N.,Sukhomazova, E. N.
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p. 755 - 760
(2007/10/02)
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- NON-STATIONARY EXPERIMENTS ON THIOPHENE AND TETRAHYDROTHIOPHENE HYDRODESULPHURIZATION
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The reactions of tetrahydrothiophene and thiophene in hydrogen on sulphided Mo/Al2O3, Co-Mo/Al2O3, and Ni-W/Al2O3 catalysts have been studied using pulse-flow, stopped flow, and started flow techniques.The composition of the effluent from the reactor was analyzed after a perturbation and the observed response curves have been interpreted from the point of view of the reaction mechanism and influence of the promotor (Co) in the Co-Mo/Al2O3 catalyst.The results confirm that at least partial saturation of the thiophene ring is necessary for hydrodesulphurization and that at least one C-S bond is splitted by hydrogenolysis, the second one either by hydrogenolysis or by elimination.Cobalt increases the hydrogenolytic activity of molybdenum, in its absence the predominant reaction of tetrahydrothiophene is dehydrogenation to thiophene.
- Moravek, Vladimir,Kraus, Milos
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p. 2159 - 2169
(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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- HIGH-TEMPERATURE ORGANIC SYNTHESIS. INVESTIGATION OF THE MECHANISM OF PYROLYSIS OF DIORGANIC SULFIDES BY THE CHLOROBENZENE TRAP METHOD
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The copyrolysis of various diorganic sulfides with chlorobenzene in the gas phase at 600-650 deg C was investigated.The degree of conversion of the chlorobenzene, which is a trap for thiyl radicals, increases with increase in the reaction temperature and depends significantly on the nature of the sulfide.The copyrolysis of chlorobenzene with branched dialkyl sulfides (secondary and tertiary) takes place more slowly than the reaction with the corresponding di(n-alkyl) sulfides.Alkyl vinyl sulfides are similar to the latter in reactivity.Ethyl β,β-dichlorovinyl sulfide and bis(ethylthio)acetylene have low reactivity.The main products from copyrolysis of all the diorganic sulfides with chlorobenzene are benzene, thiophenol, diphenyl sulfide, thiophene, and benzothiophene.The ratio between the products depends on the nature of the initial sulfide and an the temperature.The ratio between the thiophene and benzothiophene makes it possible to form an opinion about the mechanism of the formation of thiophene during the pyrolysis of the sulfides.Several paths were determined for the formation of the thiophene molecule through the thiyl radicals, and they supplemented the known mechanism of the pyrolysis of dialkyl sulfides, i.e., intermolecular cyclization of ethenethiol, intramolecular cyclization of butenethiol, cyclization of divinyl sulfide, and thermal dissociation of bis(ethylthio)acetylene.Intramolecular heterocyclization of the thiyl radicals is realized at a higher rate than intermolecular cyclization.
- Voronkov, M. G.,Deryagina, E. N.,Sukhomazova, E. N.,Mirskova, A. N.,Seredkina, S. G.
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p. 1453 - 1458
(2007/10/02)
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- HIGH-TEMPERATURE ORGANIC SYNTHESIS. XVII. REACTION OF CHLOROBENZENE AND ITS DERIVATIVES WITH DIALKYL DISULFIDES
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The products from the reaction of chlorobenzene with dialkyl disulfides in the gas phase at 550-650 deg C are benzene, thiophenol, diphenyl sulfide, and also toluene, thiophene, and benzothiophene.Diethyl disulfide is most reactive.Its copyrolysis with chlorobenzene is distinguished by high selectivity for the formation of thiophenol, the yield of which amounts to 60percent.In the reaction of substituted chlorobenzenes and also 2-chlorothiophene and 1-chloronaphthalene with diethyl disulfide the corresponding thiols were obtained with high yields.Two paths for the formation of thiophene during the pyrolysis of dialkyl disulfide were established, i.e., from vinyl hydrosulfide and S-butyl radical.The last reaction is realized at a high rate.
- Voronkov, M. G.,Deryagina, E. N.,Sukhomazova, E. N.
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p. 1516 - 1522
(2007/10/02)
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- A REGIOSPECIFIC SYNTHESIS OF CARBOSUBSTITUTED HETEROAROMATIC DERIVATIVES VIA Pd-CATALYZED CROSS COUPLING
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The Pd-catalyzed cross-coupling reaction of either heteroarylzinc derivatives with unsaturated organic halides or heteroaryl halides with organometallic reagents containing Zn or Al can produce cleanly and regiospecifically the corresponding carbo-substituted heteroatomic compounds in high yields.
- Negishi, Ei-ichi,Luo, Fen-Tair,Frisbee, Roger,Matsushita, Hajime
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p. 117 - 122
(2007/10/02)
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- CATALYTIC REDUCTIVE DEHALOGENATION OF THIOPHENE DERIVATIVES
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A method for the preparation of 3-substituted derivatives of thiophene by reductive dehalogenation of 2,5-dihalo-substituted thiophenes in the presence of a palladium complex is proposed.The dehalogenation reaction is a stepwise process.The presence of an acyl group in the 3 position increases the rate of the process.
- Sharf, V. Z.,Taits, S. Z.,Gurovets, A. S.,Vol'kenshtein, Yu. B.,Fabrichnyi, B. P.,Shcherbakova, S. I.
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p. 130 - 133
(2007/10/02)
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- Flash Vacuum Pyrolysis of Aromatic Oximes
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Flash vacuum pyrolisis (FVP) of benzaldoximes and aryl ketoximes afforded nitriles and additional aromatic compounds which were presumably generated from intermediary iminyl radicals.The FVP also gave benzoxazoles, which were presumably formed from iminoxyl radicals.Benzyl ketoximes afforded indoles together with fragmentation products of the iminyl radicals.Keyword---gas-phase pyrolysis; flash vacuum pyrolysis; FVP; flash thermolysis; oxime; iminyl radical; iminoxyl radical; substituted indole; benzoxazole; mass spectra
- Ohsawa, Akio,Kawaguchi Takayuki,Igeta Hiroshi
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p. 4352 - 4358
(2007/10/02)
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- CATALYSIS BY SULPHIDES. PART 2. TETRAHYDROTHIOPHEN HYDRODESULPHURISATION CATALYSED BY POWDERED MOLYBDENUM DISULPHIDE
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Tetrahydrothiophen hydrodesulphurisation catalysed by unsupported rhombohedral-MoS2, and by H0.07MoS2 has been investigated using deuterium as an isotopic tracer.Over MoS2 at 693 K the major products were buta-1,3-diene (mostly C4H6 and C4D6) and propadiene (C3H4); there was no exchange of H for D in the tetrahydrothiophen.Butenes formed by further hydrogenation contained a wide distribution of deuterium.The product composition at 593 K was similar, except that propadiene was not formed.Structural incorporation of hydrogen into the sulphide to give H0.07MoS2 greatly increased hydrodesulphurisation activity so that reaction was measureable at 436 K; exchange occurred at the 1- and 4-positions in the reactant, and butenes were the sole products.The deuterium distributions in the products show that tetrahydrothiophen is chemisorbed without dissociation at 436 K on H0.07MoS2, but dissociatively chemisorbed on MoS2 at 593 and 693 K.Dissociative chemisorption occurs by two routes.In the first, sulphur removal precedes dehydrogenation and hydrogenolysis giving C4H6 and C3H4 as primary products; in the second, dehydrogenation precedes sulphur removal giving adsorbed thiophen as primary product which then undergoes sulphur removal, affording butadiene and butene by hydrogenation.These processes are distinguishable because the second occurs at sites which bring about multiple exchange in a highly deuterium-rich environment, thus giving the fully deuteriated products C4D4S, C4D6, and C4D8.
- Blake, M. R.,Eyre, M.,Moyes, R. B.,Wells, P. B.
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p. 1293 - 1300
(2007/10/02)
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- HIGH - TEMPERATURE ORGANIC SYNTHESIS. XIII. THE REACTIONS OF HYDROGEN SULFIDE WITH 1,2-DICHLOROETHYLENE
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1,2-Dichloroethylene reacts with hydrogen sulfide in the gas phase at 420 - 520 deg C in an empty quartz tube, forming bis(β-chlorovinyl)sulfide (geometric isomers), 2- and 3-chlorothiophene, 2,4-dichlorothiophene, 2- and 3-thienyl β-chlorovinyl sulfides (cis and trans isomers), cis-4-chloro-2-thienyl β-chlorovinyl sulfide, and thieno- and thienothiophenes.The yields of these compounds depend on the reaction conditions (temperature, contact time, ratio of initial reagents).At 480 deg C in an excess of 1,2-dichloroethylene the yield of the mixture of2- and 3-chlorothiophene amounts to 25percent (ratio 3 : 1).
- Perevalova, V. I.,Bannikova, O. B.,Deryagina, E. N.,Voronkov, M. G.
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p. 355 - 361
(2007/10/02)
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- Hydrodesulphurization mechanism of thiophene and tetrahydrothiophene on a cobalt molybdenum catalyst
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The hydrodesulphurization mechanism of thiophene and tetrahydrothiophene has been developed at high pressures and over a broad range of temperature and contact time on a commercial CoMo-Al2O3 catalyst.The influence of the pretreatment on the catalyst activity and stability was also studied.The pretreatment with a mixture of H2 and H2S was found to be the most convenient.It was found that the sulphur uptake of the fresh catalyst increases with temperature and that an excess of sulphur in the catalyst leads to an initial higher activity.The thiophene reaction seems to occur simultaneously by two pathways: one consists of ring opening, and the second is yielding tetrahydrothiophene.The latter is the slowest step.The tetrahydrothiophene reacts faster than the thiophene and its reaction mechanism involves mainly the rupture of the C-S bond.However, thiophene was detected in small concentrations, showing the contribution of a second route for the tetrahydrothiophene hydrodesulphurization.Experiments carried out with benzene seem to indicate the existence of three different kinds of active sites in the catalyst: desulphurization, aromatics hydrogenation, and olefin saturation sites.
- Pazos, Jose M.,Andreu, Paulino
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p. 479 - 484
(2007/10/02)
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- Organosulfur Compounds, L. - 2H-Thiopyrans and Dihydro-2H-thiopyrans, Synthons for Thiophenes
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2H-Thiopyran derivatives yield thiophenes on pyrolysis at 240-260 deg C.The influence of substitution in positions 3 to 6 of the 2H-thiopyrans on these new thermal rearrangement and fragmentation reactions is dealt with, and some proposed mechanisms are discussed in detail.A novel three-step synthesis of thiophenes from carbonyl compounds via the corresponding thiones, their -cycloaddition with 1,3-dienes with formation of dihydro-2H-thiopyrans and subsequent thermal conversion is described.In this reaction sequence, whose scope and limitations are outlined, t he thiocarbonyl compound contributes the sulfur and the 1,3-diene the carbon skeleton of the desired thiophenes.
- Praefcke, Klaus,Weichsel, Christian
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p. 1604 - 1619
(2007/10/02)
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