- Investigation of the reaction network of benzofuran hydrodeoxygenation over sulfided and reduced Ni-Mo/Al2O3 catalysts
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The hydrodeoxygenation (HDO) network of benzofuran was studied over alumina-supported Ni-Mo sulfided and reduced catalysts. Over the sulfided catalyst, a major route was observed for the benzofuran HDO network. It started with the hydrogenation of benzofuran to 2,3-dihydrobenzofuran followed by its hydrogenolysis to 2-ethylphenol. However, over the reduced catalysts, an additional route was observed which begins with the hydrogenation of 2,3-dihydrobenzofuran. This route contained a number of other oxygen-containing intermediate species which were not observed over the sulfided catalyst, and hydrocarbon products were formed by this route at significantly lower temperatures. The product distribution for both catalysts was a strong function of temperature and H2S feed concentration where the hydrogenolysis reactions were promoted and the hydrogenation reactions were inhibited by H2S in the feedstream.
- Ozkan,Bunch
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Read Online
- Controlling the Lewis Acidity and Polymerizing Effectively Prevent Frustrated Lewis Pairs from Deactivation in the Hydrogenation of Terminal Alkynes
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Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3 can be easily recycled.
- Geng, Jiao,Hu, Xingbang,Liu, Qiang,Wu, Youting,Yang, Liu,Yao, Chenfei
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p. 3685 - 3690
(2021/05/31)
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- Regioselective Isomerization of Terminal Alkenes Catalyzed by a PC(sp3)Pincer Complex with a Hemilabile Pendant Arm
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We describe an efficient protocol for the regioselective isomerization of terminal alkenes employing a previously described bifunctional Ir-based PC(sp3)complex (4) possessing a hemilabile sidearm. The isomerization, catalyzed by 4, results in a one-step shift of the double bond in good to excellent selectivity, and good yield. Our mechanistic studies revealed that the reaction is driven by the stepwise migratory insertion of Ir?H species into the terminal double bond/β-H elimination events. However, the selectivity of the reaction is controlled by dissociation of the hemilabile sidearm, which acts as a selector, favoring less sterically hindered substrates such as terminal alkenes; importantly, it prevents recombination and further isomerization of the internal ones.
- De-Botton, Sophie,Filippov, D.Sc. Oleg A.,Shubina, Elena S.,Belkova, Natalia V.,Gelman, Dmitri
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p. 5959 - 5965
(2020/10/15)
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- ISOMERIZATION OF ALKENES
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The present invention relates to an isomerization method for alkenes, comprising of reaction an alkene with a Ni(I)-compound. By this method, E-Alkenes are obtained in excellent yield.
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Page/Page column 20-21; 25
(2020/04/25)
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- A nickel-iridium alloy as an efficient heterogeneous catalyst for hydrogenation of olefins
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Nickel and iridium supported on SiO2 (Ni-Ir/SiO2) acted as an effective and reusable heterogeneous catalyst for hydrogenation of olefins, and it showed higher activity and selectivity than the monometallic counterparts. The Ni-Ir/SiO2 catalyst has small Ni-Ir alloy and monometallic Ni particles, and the high catalytic performance can be attributed to the isolated Ni atom in the Ni-Ir alloys.
- Bai, Jia-qi,Tamura, Masazumi,Nakagawa, Yoshinao,Tomishige, Keiichi
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supporting information
p. 10519 - 10522
(2019/09/06)
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- E-Olefins through intramolecular radical relocation
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Full control over the selectivity of carbon-carbon double-bond migrations would enable access to stereochemically defined olefins that are central to the pharmaceutical, food, fragrance, materials, and petrochemical arenas. The vast majority of double-bond migrations investigated over the past 60 years capitalize on precious-metal hydrides that are frequently associated with reversible equilibria, hydrogen scrambling, incomplete E/Z stereoselection, and/or high cost. Here, we report a fundamentally different, radical-based approach.We showcase a nonprecious, reductant-free, and atom-economical nickel (Ni)(I)-catalyzed intramolecular 1,3-hydrogen atom relocation to yield E-olefins within 3 hours at room temperature. Remote installations of E-olefins over extended distances are also demonstrated.
- Kapat, Ajoy,Sperger, Theresa,Guven, Sinem,Schoenebeck, Franziska
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p. 391 - 396
(2019/02/03)
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- Trans -2 - substituted cycloalkyl three fluoro potassium borate synthesis method (by machine translation)
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The invention discloses trans - 2 - substituted cyclohexyl three fluoro potassium borate synthesis method, which belongs to the field of organic synthesis. From the cyclic ketone starting curing and reagent or lithium reagent addition subsequently dehydrated and gets substituted alkenes, subsequently with the catechol borane or after aminol borane addition reaction, fluorine hydride potassium direct quenching treatment to obtain trans - 2 - substituted cyclohexyl three fluoro potassium borate, the catechol borane to obtain the racemate product, [...] photoinitiators enantiomerically pure product. The method has low cost, convenient source of raw materials, the operation is simple, and has industrial amplifying of the prospect. (by machine translation)
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Paragraph 0022
(2019/04/04)
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- Cross-Linked "poisonous" Polymer: Thermochemically Stable Catalyst Support for Tuning Chemoselectivity
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Designed catalyst poisons can be deliberately added in various reactions for tuning chemoselectivity. In general, the poisons are "transient" selectivity modifiers that are readily leached out during reactions and thus should be continuously fed to maintain the selectivity. In this work, we supported Pd catalysts on a thermochemically stable cross-linked polymer containing diphenyl sulfide linkages, which can simultaneously act as a catalyst support and a "permanent" selectivity modifier. The entire surfaces of the Pd clusters were ligated (or poisoned) by sulfide groups of the polymer support. The sulfide groups capping the Pd surface behaved like a "molecular gate" that enabled exceptionally discriminative adsorption of alkynes over alkenes. H2/D2 isotope exchange revealed that the capped Pd surface alone is inactive for H2 (or D2) dissociation, but in the presence of coflowing acetylene (alkyne), it becomes active for H2 dissociation as well as acetylene hydrogenation. The results indicated that acetylene adsorbs on the Pd surface and enables cooperative adsorption of H2. In contrast, ethylene (alkene) did not facilitate H2-D2 exchange, and hydrogenation of ethylene was not observed. The results indicated that alkynes can induce decapping of the sulfide groups from the Pd surface, while alkenes with weaker adsorption strength cannot. The discriminative adsorption of alkynes over alkenes led to highly chemoselective hydrogenation of various alkynes to alkenes with minimal overhydrogenation and the conversion of side functional groups. The catalytic functions can be retained over a long reaction period due to the high thermochemical stability of the polymer.
- Yun, Seongho,Lee, Songhyun,Yook, Sunwoo,Patel, Hasmukh A.,Yavuz, Cafer T.,Choi, Minkee
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p. 2435 - 2442
(2016/04/26)
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- Z -selective alkene isomerization by high-spin cobalt(II) complexes
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The isomerization of simple terminal alkenes to internal isomers with Z-stereochemistry is rare, because the more stable E-isomers are typically formed. We show here that cobalt(II) catalysts supported by bulky β-diketiminate ligands have the appropriate kinetic selectivity to catalyze the isomerization of some simple 1-alkenes specifically to the 2-alkene as the less stable Z-isomer. The catalysis proceeds via an "alkyl" mechanism, with a three-coordinate cobalt(II) alkyl complex as the resting state. β-Hydride elimination and [1,2]-insertion steps are both rapid, as shown by isotopic labeling experiments. A steric model explains the selectivity through a square-planar geometry at cobalt(II) in the transition state for β-hydride elimination. The catalyst works not only with simple alkenes, but also with homoallyl silanes, ketals, and silyl ethers. Isolation of cobalt(I) or cobalt(II) products from reactions with poor substrates suggests that the key catalyst decomposition pathways are bimolecular, and lowering the catalyst concentration often improves the selectivity. In addition to a potentially useful, selective transformation, these studies provide a mechanistic understanding for catalytic alkene isomerization by high-spin cobalt complexes, and demonstrate the effectiveness of steric bulk in controlling the stereoselectivity of alkene formation.
- Chen, Chi,Dugan, Thomas R.,Brennessel, William W.,Weix, Daniel J.,Holland, Patrick L.
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supporting information
p. 945 - 955
(2014/02/14)
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- Ligand effect in the Rh-NP catalysed partial hydrogenation of substituted arenes
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The Rh nanoparticles Rh1-Rh4 stabilised by the mono- and bidentate phosphine and phosphite ligands I-IV were synthesised, characterised and applied as catalysts in the partial hydrogenation of substituted arenes. In the case of disubstituted arenes, selectivities for the corresponding cyclohexene derivatives of up to 39% were achieved at ca. 40% conversion. The effect of parameters such as temperature and pressure was also examined. In the hydrogenation of styrene, very high selectivities for ethylbenzene were achieved with TOF values up to ca. 23500 h-1. All these results show that the catalytic performance of small Rh-NPs can be modulated by the appropriate choice of stabilising agents.
- Castelbou, Jessica Llop,Gual, Aitor,Mercade, Elisabet,Claver, Carmen,Godard, Cyril
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p. 2828 - 2833
(2013/09/24)
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- Metal-ligand core-shell nanocomposite catalysts for the selective semihydrogenation of alkynes
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Catalysts with a sheltered upbringing: Novel core-shell nanocomposite catalysts consisting of active metal nanoparticles encapsulated by macroligands have been prepared. They have Pd nanoparticles (PdNPs) as an active core and shell ligands having sulfoxide moieties coordinated to the PdNPs. The shell protects the catalyst from coordination by alkenes and allows the lead-free selective semihydrogenation of a wide range of alkynes without any additives (see scheme). Copyright
- Mitsudome, Takato,Takahashi, Yusuke,Ichikawa, Satoshi,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 1481 - 1485
(2013/04/10)
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- Selective catalytic C-H alkylation of alkenes with alcohols
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Alkenes and alcohols are among the most abundant and commonly used organic feedstock in industrial processes. We report a selective catalytic alkylation reaction of alkenes with alcohols that forms a carbon-carbon bond between vinyl carbon-hydrogen (C-H) and carbon-hydroxy centers with the concomitant loss of water. The cationic ruthenium complex [(C6H6)(PCy 3)(CO)RuH]+BF4- (Cy, cyclohexyl) catalyzes the alkylation in solution within 2 to 8 hours at temperatures ranging from 75° to 110°C and tolerates a broad range of substrate functionality, including amines and carbonyls. Preliminary mechanistic studies are inconsistent with Friedel-Crafts-type electrophilic activation of the alcohols, suggesting instead a vinyl C-H activation pathway with opposite electronic polarization.
- Lee, Dong-Hwan,Kwon, Ki-Hyeok,Yi, Chae S.
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scheme or table
p. 1613 - 1616
(2012/02/01)
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- Effect of H2S and CO on the transformation of 2-ethylphenol as a model compound of bio-crude over sulfided Mo-based catalysts: Propositions of promoted active sites for deoxygenation pathways based on an experimental study
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Promoted (CoMo/Al2O3 and NiMo/Al2O 3) and unpromoted (Mo/Al2O3) catalysts were tested in the hydrodeoxygenation of 2-ethylphenol as a model compound of bio-crude under various partial press
- Bouvier, Christophe,Romero, Yilda,Richard, Frederic,Brunet, Sylvette
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body text
p. 2441 - 2451
(2011/10/12)
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- Synthesis and reactivity of rhodium mono-and bis(diolefin) complexes. Characterization of intermediates in the rhodium-catalyzed cyclotetramerization of butadiene
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Rhodium bis(diolefin) complexes of the general composition [Rh(η4-diene)2(L)]X (diene = butadiene, isoprene, 2,3-dimethylbutadiene; L = PiPr3, PCy3, PtBu 2Me, AsiPr3, SbiPr3, CO,
- Bosch, Marco,Werner, Helmut
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body text
p. 5646 - 5660
(2011/01/11)
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- Hydrodeoxygenation of bio-derived phenols to hydrocarbons using RANEY Ni and Nafion/SiO2 catalysts
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A simple, green, cost- and energy-efficient route for converting phenolic components in bio-oil to hydrocarbons and methanol has been developed, with nearly 100% yields. In the heterogeneous catalysts, RANEY Ni acts as the hydrogenation catalyst and Nafion/SiO2 acts as the Bronsted solid acid for hydrolysis and dehydration.
- Zhao, Chen,Kou, Yuan,Lemonidou, Angeliki A.,Li, Xuebing,Lercher, Johannes A.
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experimental part
p. 412 - 414
(2010/04/04)
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- Reduction of carbon-carbon double bonds using organocatalytically generated diimide
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(Chemical Equation Presented) An efficient method has been developed for the reduction of carbon-carbon double bonds with diimide, catalytically generated in situ from hydrazine hydrate. The employed catalyst is prepared in one step from riboflavin (vitamin B2). Reactions are carried out in air and are a valuable alternative when metal-catalyzed hydrogenations are problematic.
- Smit, Christian,Fraaije, Marco W.,Minnaard, Adriaan J.
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supporting information; experimental part
p. 9482 - 9485
(2009/04/06)
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- Ionic-liquid-like copolymer stabilized nanocatalysts in ionic liquids: II. Rhodium-catalyzed hydrogenation of arenes
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Rhodium nanoparticles stabilized by the ionic-liquid-like copolymer poly[(N-vinyl-2-pyrrolidone)-co-(1-vinyl-3-butylimidazolium chloride)] were used to catalyze the hydrogenation of benzene and other arenes in ILs. The nanoparticle catalysts can endure forcing conditions (75 °C, 40 bar H2), resulting in high reaction rates and high conversions compared with other nanoparticles that operate in ILs. The hydrogenation of benzene attained record total turnovers of 20,000, and the products were easily separated without being contaminated by the catalysts. Other substrates, including alkyl-substituted arenes, phenol, 4-n-propylphenol, 4-methoxylphenol, and phenyl-methanol, were studied and in most cases were found to afford partially hydrogenated products in addition to cyclohexanes. In-depth investigations on reaction optimization, including characterization of copolymers, transmission electron microscopy, and an infrared spectroscopic study of nanocatalysts, were also undertaken.
- Zhao, Chen,Wang, Han-zhi,Yan, Ning,Xiao, Chao-xian,Mu, Xin-dong,Dyson, Paul J.,Kou, Yuan
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- The preparation of silica entrapped homogeneous hydrogenation catalysts by conventional and ionic liquid mediated sol-gel routes
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[RhCl(PPh3)3] has been entrapped inside silica matrices by two methods: a conventional sol-gel synthesis in ethanol/water and a new route performed in an ionic liquid. The activity of these heterogenised catalysts has been tested for the hydrogenation of styrene. The catalyst prepared in an ionic liquid was found to be more active and have low Rh leaching.
- Craythorne, Steven J.,Crozier, Alan R.,Lorenzini, Fabio,Marr, Andrew C.,Marr, Patricia C.
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p. 3518 - 3521
(2007/10/03)
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- Process for preparing acrylate compound
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An acrylate compound of formula (4): 1is produced by allowing an acrylic acid compound of formula (1): 2to react with an unsaturated compound of formula (2) or (3): 3In formulae (1) through (4), R1 and R2 are H or F, R3 is H, F, or an alkyl, alkenyl, fluoroalkyl or fluoroalkenyl group, R4 and R5 are H, halogen, or an alkyl, alkenyl, halogenated alkyl or halogenated alkenyl group; and X and Y are an unsubstituted or substituted hydrocarbon group, and dashed line - - - - - means that X and Y may be bonded together to form a cyclic structure.
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- Oxidative dehydrogenation of saturated hydrocarbons in the presence of polyoxotungstates
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Polyoxotungstates of the formulas K5FeSi(OH2)W11O39 · 3H2O and Na6MnSi(OH2)W11O39 supported on Al2O3 were studied as catalysts for oxidative transformations of n-heptane, isooctane, cyclohexane, ethylcyclohexane, cyclooctane, decalin, and bicyclohexyl at 150-250°C and a contact time of 2-6 s in an air or helium flow. As a rule, unsaturated hydrocarbons with the same number of carbon atoms were formed. Isooctane underwent partial decomposition. Oxygenated compounds were not found. In the case of monocyclic compounds, dehydrogenation is accompanied to an insignificant extent by ring opening to yield linear dienes. Hydrocarbons with six-membered cycles (with the exception of unsubstituted cyclohexane) are partially dehydrogenated to aromatic compounds. The yield of dehydrogenation products on the iron-containing catalyst decreases in the order: decalin > bicyclohexyl > ethylcyclohexane > cyclohexane > n-heptane > cyclooctane. The use of H2O2 as an oxidant (200°C, 6 s) strongly increases the yield of the dehydrogenation products on Fe polyoxotungstate, especially in the case of bicyclohexyl and decalin.
- Nekhaev,Borisov,Zaikin,Bagrii
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p. 418 - 422
(2007/10/03)
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- Selective liquid-phase semihydrogenation of functionalized acetylenes and propargylic alcohols with silica-supported bimetallic palladium-copper catalysts
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Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated. Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated.
- Spee,Boersma,Meijer,Slagt,Van Koten,Geus
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p. 1647 - 1656
(2007/10/03)
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- Reactions of tertiary alcohols with palladium(II) tetraaqua complex. Formation of palladium π-allyl complexes
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Transformations of 2-methyl-2-propanol, 2-methyl-2-butanol, 2-methyl-2-pentanol, 1-methyl-1-cyclohexanol, and 1-ethyl-1-cyclohexanol in the presence of tetraaquapalladium(II) ions in perchloric acid madium were studied. It was found that the reactions give rise to palladium(II) π-allyl complexes. The reaction rate increases and the yield of the corresponding π-allyl complex decreases with increasing hydrocarbon chain length. Addition of iron(III) ions to the systems essentially increases the yield of palladium π-allyl complexes. The olefin formed from the corresponding tertiary alcohol participates in the formation of the palladium π-allyl complex. Oxidation of 2-methyl-2-butanol with tetraaquapalladium(II) ions gives the isomeric palladium π-allyl complexes [Pd(η3-(CH3)2CCHCH2)bpy]ClO 4 and [Pd(η3-(CH2C(CH3)CHCH 3))bpy]ClO4, which were isolated using 2,2'-bipyridyl and characterized by 1H and 13C NMR spectroscopy.
- Potekhin,Ryadinskaya,Potekhin
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p. 1169 - 1175
(2007/10/03)
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- Hydrodenitrogenation activities of methyl-substituted indoles
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The HDN reactivities of indole and several methyl-substituted indoles were obtained over a NiMo/Al2O3 catalyst and a CoMo/Al2O3 catalyst using a fixed-bed reactor at 340°C and 31 atm hydrogen pressure. A methyl
- Massoth,Kim
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- Composition of Mixtures of Hydrocarbons after BIRCH-Reduction of Substituted Benzenes and Acid Catalyzed Addition of Alcohols to Alkylsubstituted Cyclohexenes and Carbohexa-1,4-dienes
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10 different benzene hydrocarbons 1, indane, tetraline, anisol and phenol are reduced by sodium in liquid ammonia in the presence of methanol to the BIRCH products 2.The product mixture compositions are determined through capillary GLC.On storage at +6 deg C some rearomatization of the 1,4-cyclohexadienes 2 occurs.Data of the 1H- and 13C-.n.m.r. spectra and also mass spectra of the BIRCH 1,4-dienes 2 are given.For comparison 4-alkoxycyclohexenes 4 and 1-alkoxy-1-methylcyclohexanes 8 are prepared and spectroscopically characterized.Acid-catalyzed addition of alcohols to the 1,4-cyclohexadienes systems is a slow process and gives the 4-alkoxy-4-alkylcyclohex-1-enes (4) only in moderate yields up to 30percent.Most of the products are dimers 5 and also oligomers 6 of the parent hydrocarbons 2.
- Beger, J.,Thomas, B.,Vogel, T.,Kirmse, K.,Lang, R.
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p. 481 - 488
(2007/10/02)
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- Regioselective Hydrogenation of Conjugated Dienes Catalyzed by Hydridopentacyanocobaltate Anion using β-Cyclodextrin as the Phase-Transfer Agent and Lanthanide Halides as Promotors
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β-Cyclodextrin is a useful phase-transfer agent for the hydrogenation of conjugated dienes to monoolefins catalyzed by the in situ generated hydridopentacyanocobaltate anion.This reaction, which usually proceeds by 1,2-addition to the diene, is promoted by cerium or lanthanum chloride.Polyethyleneglycol (PEG-400), with or without added lanthanide, can also used as the phase-transfer agent for the reduction process.
- Lee, Jong-Tae,Alper, Howard
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p. 1854 - 1856
(2007/10/02)
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- Photochemical Dehydrogenation of Alkanes Catalyzed by trans-Carbonylchlorobis(trimethylphosphine)rhodium: Aspects of Selectivity and Mechanism
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The photochemical dehydrogenation of alkanes is catalyzed in solution by trans-Rh(PMe3)2(CO)Cl with high efficiency; quantum yields up to 0.10 and turnover numbers as high as 5000 are achieved with cyclooctane as substrate.The intramolecular regioselectivity of the reaction is investigated with methyl-, ethyl-, and isopropylcyclohexane.In competition experiments, cyclooctane is found to be 17 times as reactive as cyclohexane; under carbon monoxide atmosphere, the selectivity is enhanced to a factor of 130.A kinetic isotope effect, kH/kD=5.3, is found for thedehydrogenation of C6H12/C6D12.Both intra- and intermolecular selectivities are consistent with a pathway involving a reversible C-H oxidative addition followed by a β-hydrogen elimination. trans-Rh(PMe3)2(CO)Cl is demonstrated to be the only significant photoactive species in solution.The dehydrogenation reaction is quenched by carbon monoxide with Stern-Volmer kinetics.On the basis of these results, a mechanism is proposed in which the enrgy needed to drive these thermodynamically unfavorable dehydrogenations is obtained only from Rh-CO bond photolysis.
- Maguire, John A.,Boese, William T.,Goldman, Alan S.
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p. 7088 - 7093
(2007/10/02)
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- KINETICS FOR SIMULTANEOUS HDS, HDN AND HYDROGENATION MODEL REACTIONS ON A Co-Mo/Al2O3 CATALYST
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A kinetic analysis of simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT), hydrodenitrogenation (HDN) of indole (IN) and hydrogenation (HYD) of naphthalene (NAP) is carried out.These compounds represent the major functional groups in heavy petroleum feeds.The goal of these experiments is to simulate the performance of a commercial catalyst with more complex feedstocks.The purposes are to determine the competitive inhibition effects of the various reactants as well as to investigate a microscopic model which can be generalized to more realistic feedstocks.Kinetic data are generated over a CoMo/Al2O3 catalyst in a temperature range of 260-350 deg C and total pressure of 25-81 105 Pa.The partial pressures of hydrogen and the other reactants are varied individually.From the data, a kinetic model is developed based on the competitive chemisorption of reactants, intermediates and products on identical surface sites.The kinetic model developed accounts for rates of appearance of the products and rates of disappearance of DBT, NAP and IN.The results suggest that compounds containing sulfur, nitrogen, aromatics or aliphatics are adsorbed with very different strength.
- Zeuthen, Per,Stolze, Per,Pedersen, Ulla B.
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p. 985 - 996
(2007/10/02)
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- Protium-deuterium exchange of cyclic and acyclic alkanens in dilute acid medium at elevated temperatures
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A modification of the high temperature - dilute acid (HTDA) method for deuterium labelling of aromatic compounds has been applied to the H-D exchange of a number of cyclic and acyclic alkenes.Cyclopentene, cyclohexene, cyclododecene, and tetramethylethylene have been completely exchanged in excellent yield. 1-Methylcyclopentene and 1-methylcyclohexene have also been perdeuterated and cycloheptene and cyclooctene partially labelled but require spinning band distillation or preparative glpc for separation from rearrangement products.A variety of C5-C8 acyclic alkeneshave also been treated under HTDA conditions.
- Werstiuk, Nick Henry,Timmins, George
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p. 530 - 533
(2007/10/02)
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- Deuterium Isotope Effects for Migrating and Nonmigrating Groups in the Solvolysis of Neopentyl-Type Esters
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α- and γ-deuterium rate effects on the solvolysis of (1-methylcyclohexyl)methyl, (1-methylcyclopentyl)methyl, and (1-methylcyclobutyl)methyl sulfonate esters have been measured and the solvolysis products examined by 2H NMR spectroscopy.The results indicate that the products of the solvolysis of all these sulfonate esters are predominantely ((*) 98percent) rearranged.In the solvolysis of (1-methylcyclohexyl)methyl triflate, rearranged products with methyl migration slightly dominate over those with ring expansion.Normal isotope effects, 1.057 in 80E and 1.073 in 97T, are observed for the methyl-d3 compound and an inverse effect, 0,963, is observed in 80E for the methylene-d4 compound.However, in the solvolysis of both (1-methylcyclopentyl)methyl and (1-methylcyclobutyl)methyl sulfonates, the major products are those of ring expansion.In these examples, inverse effects are observed for the methyl-d3-labeled species.The observed isotope effects can be separated into respective values of 0.927, 0.913 for the nonmigrating methyl-d3 group and 1.177, 1.224 for the migrating methyl-d3 group in the solvolysis of (1-methylcyclohexyl)methyl triflate and (1-methylcyclopentyl)methyl brosylate.This explains the relative intramolecular migratory aptitudes of CH3/CD3 of 1.20 - 1.30 and the low γ-d9 isotope effect in the solvolysis of neopentyl sulfonates previously reported and makes them consistent with a mechanism which involves neighboring carbon participation during ionization.
- Shiner, V. J.,Tai, Jimmy J.
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p. 436 - 442
(2007/10/02)
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- Some studies on the solvolysis of 1-chloro-1-alkyl cycloalkanes
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The effect of the bulk of the sidechain on the rate of solvolysis of 1-alkyl cyclopentyl, cyclohexyl, and cycloheptyl chlorides has been studied.With the exception of the t-butyl systems, the ratio of solvolysis rates for the three ring systems falls in a given series.The slower rate of solvolysis in the six-membered ring system may be due to an extra activation energy contribution caused by the conversion of a neutral chair form to the twist boat or half chair conformation, prior to the actual solvolysis.In the case of five- and seven-membered ring systems the formation of an intermediate carbonium ion is sterically favoured (I-strain or eclipsing interaction) consistent with earlier findings.The faster rate of solvolysis of 1-t-butylcycloalkyl chlorides is likely due to a rearrangement reaction where alkyl participation enhances the rate of solvolysis.
- Ranganayakulu, K.,Vasumathi Devi, M.,Balaji Rao, R.,Rajeswari, K.
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p. 1484 - 1489
(2007/10/02)
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- Synthesis of Olefins from α-Chlorocarbonyl Compounds
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Olefins or diolefins with the double bonds in predetermined positions are obtained in moderate to good yields by treatment of α-chlorocarbonyl compounds with Grignard reagents and lithium in a single process.
- Barluenga, Jose,Yus, Miguel,Concellon, Jose M.,Bernad, Pablo
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p. 677 - 692
(2007/10/02)
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