- 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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- CoPd Nanoalloys with Metal–Organic Framework as Template for Both N-Doped Carbon and Cobalt Precursor: Efficient and Robust Catalysts for Hydrogenation Reactions
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In this work, a series of metal–organic framework (MOF)-derived CoPd nanoalloys have been prepared. The nanocatalysts exhibited excellent activities in the hydrogenation of nitroarenes and alkenes in green solvent (ethanol/water) under mild conditions (H2 balloon, room temperature). Using ZIF-67 as template for both carbon matrix and cobalt precursor coating with a mesoporous SiO2 layer, the catalyst CoPd/NC@SiO2 was smoothly constructed. Catalytic results revealed a synergistic effect between Co and Pd components in the hydrogenation process due to the enhanced electron density. The mesoporous SiO2 shell effectively prevented the sintering of hollow carbon and metal NPs at high temperature, furnishing the well-dispersed nanoalloy catalysts and better catalytic performance. Moreover, the catalyst was durable and showed negligible activity decay in recycling and scale-up experiments, providing a mild and highly efficient way to access amines and arenes.
- Zhu, Jie,Xu, Deng,Ding, Lu-jia,Wang, Peng-cheng
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p. 2707 - 2716
(2021/01/21)
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- Chemoselective Hydrogenation of Olefins Using a Nanostructured Nickel Catalyst
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The selective hydrogenation of functionalized olefins is of great importance in the chemical and pharmaceutical industry. Here, we report on a nanostructured nickel catalyst that enables the selective hydrogenation of purely aliphatic and functionalized olefins under mild conditions. The earth-abundant metal catalyst allows the selective hydrogenation of sterically protected olefins and further tolerates functional groups such as carbonyls, esters, ethers and nitriles. The characterization of our catalyst revealed the formation of surface oxidized metallic nickel nanoparticles stabilized by a N-doped carbon layer on the active carbon support.
- Klarner, Mara,Bieger, Sandra,Drechsler, Markus,Kempe, Rhett
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supporting information
p. 2157 - 2161
(2021/05/21)
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- Hydrogen-Catalyzed Acid Transformation for the Hydration of Alkenes and Epoxy Alkanes over Co-N Frustrated Lewis Pair Surfaces
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Hydrogen (H2) is widely used as a reductant for many hydrogenation reactions; however, it has not been recognized as a catalyst for the acid transformation of active sites on solid surface. Here, we report the H2-promoted hydration of alkenes (such as styrenes and cyclic alkenes) and epoxy alkanes over single-atom Co-dispersed nitrogen-doped carbon (Co-NC) via a transformation mechanism of acid-base sites. Specifically, the specific catalytic activity and selectivity of Co-NC are superior to those of classical solid acids (acidic zeolites and resins) per micromole of acid, whereas the hydration catalysis does not take place under a nitrogen atmosphere. Detailed investigations indicate that H2 can be heterolyzed on the Co-N bond to form Hδ-Co-N-Hδ+ and then be converted into OHδ-Co-N-Hδ+ accompanied by H2 generation via a H2O-mediated path, which significantly reduces the activation energy for hydration reactions. This work not only provides a novel catalytic method for hydration reactions but also removes the conceptual barriers between hydrogenation and acid catalysis.
- Deng, Qiang,Deng, Shuguang,Gao, Ruijie,Li, Xiang,Tsang, Shik Chi Edman,Wang, Jun,Zeng, Zheling,Zou, Ji-Jun
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p. 21294 - 21301
(2021/12/17)
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- Novel CoNi-metal-organic framework crystal-derived CoNi?C: Synthesis and effective cascade catalysis
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Evaluating the catalytic influence of metal sites on derivates obtained from the calcination of metal-organic frameworks (MOFs) is very important for the rational construction of novel MOFs. Based on this catalytic functional guidance, two new Co-MOF and CoNi-MOF crystals were designed and synthesized, and further pyrolyzed to obtain corresponding porous carbon-based catalysts. Interestingly, the derivates exhibited better catalytic performance toward the tandem reaction of dehydrogenation of NH3BH3 and subsequent hydrogenation reduction of nitro/olefin compounds than those of the CoNi-ZIF (a star MOF)-derived CoNi?carbon and most metal catalysts. Significantly, the CoNi?C maintained excellent activity, even after 30 cycles, demonstrating its great longevity and durability, which are especially important for the practical application of metal catalysts in industrial catalysis.
- Chen, Yu-Zhen,Li, Chenchen,Sun, Jia-Lu,Wang, Guo-Ming,Wang, Lin,Zhang, Jian-Wei
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supporting information
p. 10567 - 10573
(2020/09/18)
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- Murahashi Cross-Coupling at ?78 °C: A One-Pot Procedure for Sequential C?C/C?C, C?C/C?N, and C?C/C?S Cross-Coupling of Bromo-Chloro-Arenes
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The coupling of organolithium reagents, including strongly hindered examples, at cryogenic temperatures (as low as ?78 °C) has been achieved with high-reactivity Pd-NHC catalysts. A temperature-dependent chemoselectivity trigger has been developed for the selective coupling of aryl bromides in the presence of chlorides. Building on this, a one-pot, sequential coupling strategy is presented for the rapid construction of advanced building blocks. Importantly, one-shot addition of alkyllithium compounds to Pd cross-coupling reactions has been achieved, eliminating the need for slow addition by syringe pump.
- Sinha, Narayan,Heijnen, Dorus,Feringa, Ben L.,Organ, Michael G.
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supporting information
p. 9180 - 9184
(2019/07/04)
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- MICROCAPSULES AND PROCESSES FOR THEIR PREPARATION
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The present invention provides microcapsules encapsulating hydrophilic or hydrophobic active agents in an inorganic shell, processes for their preparation and compositions comprising them.
- -
-
Page/Page column 43-45
(2019/06/11)
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- Reevaluation of the Palladium/Carbon-Catalyzed Decarbonylation of Aliphatic Aldehydes
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An improved method for the decarbonylation of aliphatic aldehydes by using a commercially available Pd/C catalyst is described. The reaction conditions are suitable for linear, cyclic, or sterically demanding substrates, as they afford the corresponding alkanes in yields of up to 99%. In addition, this Pd/C-catalyzed method exhibits good functional-group tolerance. A comparison of previously reported methods with the present one showed that the reaction conditions play a crucial role in the outcome of the reaction. The method can also be applied in a two-step reaction sequence for the synthesis of industrially important compounds.
- Ajda?i?, Vladimir,Nikoli?, Andrea,Kerner, Michael,Wipf, Peter,Opsenica, Igor M.
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supporting information
p. 1781 - 1785
(2018/08/12)
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- A Co2B Mediated NaBH4 Reduction Protocol Applicable to a Selection of Functional Groups in Organic Synthesis
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A high-yielding and high-rate reduction method that operates with alkenes, alkynes, azides, nitriles, and nitroarenes was developed and optimized. The method makes use of sodium borohydride reduction of CoSO4 under release of hydrogen along with the formation of Co2B as a nanoparticle material. The produced Co2B activates the various functional groups for hydride reduction. The protocol was proven to operate with an assortment of functional groups to provide good to excellent yields. Furthermore, the reduction method was successfully adapted, implemented, and developed for a continuous flow approach using the multi-jet oscillating disk (MJOD) flow reactor platform at atmospheric pressure.
- Lundevall, Frida Johanne,Elumalai, Vijayaragavan,Drageset, Audun,Totland, Christian,Bj?rsvik, Hans-René
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supporting information
p. 3416 - 3425
(2018/07/29)
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- Phosphine-free cobalt pincer complex catalyzed: Z -selective semi-hydrogenation of unbiased alkynes
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Herein, we report a novel, molecularly defined NNN-type cobalt pincer complex catalyzed transfer semi-hydrogenation of unbiased alkynes to Z-selective alkenes. This unified process is highly stereo- and chemo-selective and exhibits a broad scope as well as wide functional group tolerance. Ammonia-borane (AB), a bench-stable substrate with high gravimetric hydrogen capacity, was used as a safe and practical transfer hydrogenating source.
- Landge, Vinod G.,Pitchaimani, Jayaraman,Midya, Siba P.,Subaramanian, Murugan,Madhu, Vedichi,Balaraman, Ekambaram
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p. 428 - 433
(2018/02/07)
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- Rhodium(i) diphenylphosphine complexes supported on porous organic polymers as efficient and recyclable catalysts for alkene hydrogenation
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This paper describes the synthesis and characterization of porous polymeric materials as a support for rhodium(i) cationic coordination compounds and their use as heterogeneous catalysts for alkene hydrogenation. The synthetic strategy was the insertion of a vinyl-moiety in a bis(2-chloroethyl)amine precursor to provide highly porous resins with an enriched modifiable surface. The precursors synthesized were N,N-bis(2-chloroethyl)prop-2-en-1-amine (Alk-POL) and N,N-bis(2-chloroethyl)acrylamide (Acy-POL). The resins were obtained through suspension polymerization of methyl acrylate and divinylbenzene as a co-polymer and cross-linker, respectively. The resin surfaces were functionalized with diphenylphosphine groups followed by Rh(i) metal deposition using [Rh(COD)2]BF4 (COD = 1,5-cyclooctadiene) as the catalyst precursor. The Rh-catalysts were characterized by different physicochemical techniques and assessed for their catalytic performances in the heterogeneous hydrogenation of styrene and its derivatives. It was found that the catalytic activities and selectivity of the heterogenized rhodium complex (Rh-Alk-POL and Rh-Acy-POL) in the hydrogenation reactions were comparable to its homogeneous analogue. Analysis of the spent homogeneous resin Rh-Alk-POL catalyst after the first reaction cycle showed the presence of metallic Rh nanoparticles arising from the reduction of the Rh complex. Extensive recycling and Rh leaching studies were carried out for the Rh-Acy-POL catalyst. Both the activity and selectivity could be maintained for at least seven reaction runs and without metal leaching during the reaction cycles. We have also studied the liquid-phase hydrogenation reaction of various styrene m-substituted derivatives. The Rh-Acy-POL catalyst exhibits excellent catalytic activity for hydrogenation of the substrates and only vinyl-group hydrogenation was detected. Finally, the presence of electron-donating/-withdrawing substituents at the meta-position resulted in different rates of vinyl group hydrogenation. This effect was quantified in terms of the Hammett relationship, in which the catalyst displayed a linear correlation between the Hammett substituent constant (σmeta) and the hydrogenation rate.
- Campos, Cristian H.,Belmar, Julio B.,Jeria, Solange E.,Urbano, Bruno F.,Torres, Cecilia C.,Alderete, Joel B.
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p. 3398 - 3407
(2017/01/24)
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- Cu(II)/Cu(0)@UiO-66-NH2: Base metal@MOFs as heterogeneous catalysts for olefin oxidation and reduction
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Two copper-loaded MOF materials, namely Cu(ii)@Ui-O-66-NH2 (1) and Cu(0)@UiO-66-NH2 (2), are reported. They can, respectively, serve as highly efficient heterogeneous catalysts for olefin oxidation and hydrogenation under mild conditions. Complete styrene hydrogenation occurs in 15 min at ambient temperature with quantitative yield.
- Wang, Jian-Cheng,Hu, Yu-Hong,Chen, Gong-Jun,Dong, Yu-Bin
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p. 13116 - 13119
(2016/11/09)
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- Rhenium-mediated dehydrogenative silylation and highly regioselective hydrosilylation of nitrile substituted olefins
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The rhenium (I) complex [Re(CH3CN)3Br 2(NO)] catalyzes the homogeneous hydrosilylation of a variety of substituted acrylonitriles, which were converted into the corresponding silyl-substituted alkanes with high regioselectivity of up to 94%. The products were analyzed by 1H NMR and GC-MS. A rhenium specific mechanism is proposed for the hydrosilylation of olefins.
- Dong, Hailin,Jiang, Yanfeng,Berke, Heinz
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- Ligand-metal cooperating PC(sp3)P pincer complexes as catalysts in olefin hydroformylation
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Ligand-metal cooperation: A new ligand-metal cooperating catalyst for the hydroformylation of olefins is described (see scheme). The mechanism of the H2 activation and C-H bond formation of the catalyst involves an intramolecular cooperation between the structurally remote functionality and the metal center and proceeds without change of the oxidation state of the metal.
- Musa, Sanaa,Filippov, Oleg A.,Belkova, Natalia V.,Shubina, Elena S.,Silantyev, Gleb A.,Ackermann, Lutz,Gelman, Dmitri
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supporting information
p. 16906 - 16909
(2014/01/06)
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- Highly efficient iron(0) nanoparticle-catalyzed hydrogenation in water in flow
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Highly efficient catalytic hydrogenations are achieved by using amphiphilic polymer-stabilized Fe(0) nanoparticle (Fe NP) catalysts in ethanol or water in a flow reactor. Alkenes, alkynes, aromatic imines and aldehydes were hydrogenated nearly quantitatively in most cases. Aliphatic amines and aldehydes, ketone, ester, arene, nitro, and aryl halide functionalities are not affected, which provides an interesting chemoselectivity. The Fe NPs used in this system are stabilized and protected by an amphiphilic polymer resin, providing a unique system that combines long-term stability and high activity. The NPs were characterized by TEM of microtomed resin, which established that iron remains in the zero-valent form despite exposure to water and oxygen. The amphiphilic resin-supported Fe(0) nanoparticles in water and in flow provide a novel, robust, cheap and environmentally benign catalyst system for chemoselective hydrogenations.
- Hudson, Reuben,Hamasaka, Go,Osako, Takao,Yamada, Yoichi M. A.,Li, Chao-Jun,Uozumi, Yasuhiro,Moores, Audrey
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p. 2141 - 2148
(2013/09/24)
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- The use of ultrasmall iron(0) nanoparticles as catalysts for the selective hydrogenation of unsaturated C-C bonds
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The performance of well-defined ultrasmall iron(0) nanoparticles (NPs) as catalysts for the selective hydrogenation of unsaturated C-C and CX bonds is reported. Monodisperse iron nanoparticles of about 2 nm size are synthesized by the decomposition of {Fe(N[Si(CH3)3]2) 2}2 under dihydrogen. They are found to be active for the hydrogenation of various alkenes and alkynes under mild conditions and weakly active for CO bond hydrogenation.
- Kelsen, Vinciane,Wendt, Bianca,Werkmeister, Svenja,Junge, Kathrin,Beller, Matthias,Chaudret, Bruno
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p. 3416 - 3418
(2013/05/22)
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- Unexpected chemoselective debromination and reduction of 1,1-dibromo-1-alkenes mediated by samarium metal in methanol
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An unexpected samarium metal mediated chemoselective debromination and reduction of 1,1-dibromo-1-alkenes in methanol has been developed, which generates vinyl monobromides, alkenes, and alkanes respectively with appropriate molar ratio of samarium to 1,1-dibromo-1-alkene.
- Wang, Lei,Li, Pinhua,Xie, Yuanyuan,Ding, Yanbin
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p. 1137 - 1140
(2007/10/03)
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- Direct Formation of (Haloaryl)copper Nucleophiles from Haloiodobenzenes and Active Copper
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(o-Halophenyl)-, (m-halophenyl)-, and (p-halophenyl)copper reagents have been formed in moderate to high yields at room temperature from active copper and the corresponding haloiodobenzenes.These reagents have been cross-coupled with a variety of alkyl and acyl halides to produce the respective haloarenes and haloaryl ketones.Remarkably, (o-fluorophenyl)- and (o-chlorophenyl)copper are produced in good yields by this procedure without undergoing elimination to form benzyne making this approach a convenient method for generating o-halophenyl nucleophiles.
- Ebert, Greg W.,Pfennig, Deborah R.,Suchan, Scott D.,Donovan, Thomas A.,Aouad, Emmanuel,et al.
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p. 2361 - 2364
(2007/10/02)
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- Facile Hydrodehalogenation with H2 and Pd/C Catalyst under Multiphase Conditions. 2. Selectivity and Kinetics
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Hydrodehalogenation of polyhalogenated aromatics with Pd/C catalyst carried out in the presence of a quaternary onium salt follows zero-order kinetics in the substrate and first-order kinetics in the Pd/C catalyst; the related rate constants were determined for o-, m- and p-bromotoluenes, o-, m- and p-chloroalkylbenzenes (methyl, ethyl, and propyl derivatives), and other aryl halides.Reaction rates, depending on the aromatic to be reduced, may be strongly enhanced by the presence of quaternary onium salts: the isomeric chloroethylbenzenes were reduced 50 times faster when operating in the presence of Aliquat 336 (1).Also the hindered 2-chloro-m-xylene easily yielded m-xylene.The cocatalyst onium salts operate by being adsorbed on the Pd/C surface, as shown when kinetic constants are reported by varying the onium salt amount: classical Langmuir adsorption isotherms are observed.The presence of the onium salt may also influence selectivity in the reduction of isomeric aryl halides: when 1 is present, p-dichlorobenzene reacts in diethyl ether at 20 deg C, 5-fold slower than the ortho isomer; whereas the reduction rates of the two compounds are almost the same in its absence.
- Marques, Carlos Alberto,Selva, Maurizio,Tundo, Pietro
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p. 3830 - 3837
(2007/10/02)
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- Versatility of Zeolites as Catalysts for Ring or Side-Chain Aromatic Chlorinations by Sulfuryl Chloride
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Zeolites catalyze chlorination of aromatics by sulfuryl chloride SO2Cl2.It is possible by an appropriate choice of the catalyst to effect at will, with very high selectivity, either the ring or the side-chain chlorination.Zeolite ZF520 is the choice catalyst for the former, because of its high Broensted acidity.Zeolite NaX (13X) is a fine catalyst for the latter, free-radical chlorination; the reaction is best effected in the presence of a light source; the catalyst can be reused many times with no loss in activity.Both reaction modes, the ionic (ring chlorination)and the radical (side-chain substitution), are likely to occur outside of the channel network in the microporous solid.The effects of various experimental factors - such as the nature of the solvent, the reaction time and temperature, the Broensted acidity of the solid support, the presence of radical inhibitors, and the quantity of catalysts - were investigated.The procedures resulting from this study are very easy to implement in practice and are quite effective.
- Delaude, Lionel,Laszlo, Pierre
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p. 5260 - 5269
(2007/10/02)
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- Alkylation of Arenes with Ethylene over H-ZSM-5 and Modernite-H Catalysis
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Attempts were made to alkylate acetophenone, benzene, benzonitrile, bromobenzene, chlorobenzene, ethylbenzene, fluorobenzene, iodobenzene, methoxybenzene, nitrobenzene, toluene and α,α,α-trifluorotoluene with ethylene over H-ZSM-5 and mordenite-H catalysts at 400 and 250 deg C, respectively.Over H-ZSM-5 benzene, bromobenzene, chlorobenzene, ethylbenzene and toluene gave monoethylarenes as the major product (95-100percent) with the para product as the dominant isomer (87-95percent).Over mordenite-H benzene, bromobenzene, chlorobenzene and toluene reacted.The monoethylarenes were again the major product (85-95percent) but the isomer distributions were close to the thermodynamically controlled ones due to isomerization of the initially formed products.Over H-ZSM-5 the results indicated the reaction to be of a Friedel-Crafts type.It was proposed that the product composition was determined by the chemical reaction, not by the rate of diffusion of the products.
- Akervold, Idar,Bakke, Jan M.,Steinsvik, Eirik
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p. 437 - 444
(2007/10/02)
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- EFFECT OF SOLVENT VISCOSITY ON THE REACTION OF STYRENES WITH HCo(CO)4 AND CO
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Changing the solvent from octane to Nujol in the reaction of styrenes with HCo(CO)4 and CO only slightly decreases the overall rates but significantly enhances carbonylation at the expense of hydrogenatioon.This effect provides further support for the view that a geminate radical pair is an intermediate in the reaction.
- Ungvary, Ferenc,Marko, Laszlo
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p. 411 - 414
(2007/10/02)
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- Low-Resolution Microwave Studies of Substituted Ethyl- and Isopropylbenzenes
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A single conformation exists in ethylbenzenes with the ethyl C-C bond lying in a plane orthogonal to the benzene ring.This conclusion results from the observation that asymmetrically substituted ethylbenzenes each display only a single band series in low-resolution microwave (LRMW) spectra whereas any other conformation of the ethylphenyl fragment would result in two spectroscopically distinguishable species.LRMW spectra of isopropylbenzene derivatives display three spectroscopically distinguishable band series, two of which correspond to the conformation with the methine C-H bond eclipsed with the benzene ring and syn or anti with respect to an unsymmetrical phenyl substituent.The third series is much more intense, has a B + C value which is the average of the syn and anti forms, and is consistent with the superposition of spectra of torsionally excited species.
- True, Nancy S.,Farag, Maya, S.,Bohn, Robert K.,MacGregor, Malcolm A.,Radhakrishnan, J.
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p. 4622 - 4627
(2007/10/02)
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- Alkyltrifluoromethanesulphonates as alkylating reagents for aromatic compounds
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Methyl and ethyl trifluoromethanesulphonates (' triflates '), prepared by conventional routes involving either trifluoromethanesulphonic acid (' triflic acid ') or its anhydride, contain traces of triflic acid as an impurity, which catalyse their alkylation reactions with aromatic compounds. Pure methyl triflate, obtained from reaction between CH3l and CFS03Ag, does not alkylate p-cymene after several hours at 100 °C. Pure ethyl triflate, prepared by a similar method, is thermally less stable under these conditions, and alkylation takes place only after long induction periods during which some breakdown to triflic acid occurs. With aromatic substrates such as p-cymene or mesitylene the onset of alkylation is followed rapidly by the formation of isomerisation and disproportionation products. Benzyl triflate, prepared from PhCH2Br and CF3SO3Ag, alkylates p-cymene even at room temperature. The strong Lewis acids SbF5 and AlCl3 similarly catalyse alkylation reactions of methyl and ethyl triflates, but BF3, FeCl3, and SnCl4 are much less effective.
- Booth, Brian L.,Haszeldine, Robert N.,Laali, Khosrow
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p. 2887 - 2893
(2007/10/02)
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