- Kinetics and mechanism of benzyl chloride reaction with zinc in dimethylacetamide
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Oxidative dissolution of zinc in the system of benzyl chloride- dimethylacetamide was investigated. The reaction stereochemistry as well as intermediates and reaction products formed were studied. The kinetic and thermodynamic parameters of the process were measured. The process was shown to follow the Langmuir-Hinshelwood mechanism with the formation of benzyl radicals and mono-solvated organozinc compound on the zinc surface. The components of mixture are adsorbed at various sites of the zinc surface, while recombination and the isomerization of the benzyl radicals occurs in solution. Pleiades Publishing, Ltd., 2012.
- Egorov,Matyukhova,Dashkova
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Read Online
- Reaction of benzyl bromide with Mn(0) in dimethylformamide
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The reaction of Mn(0) with benzyl bromide in dimethylformamide was studied.
- Egorov,Matyukhova,Nikishova,Platonov,Proskuryakov
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Read Online
- Deuterium isotope effects on the CH stretching overtone spectrum of toluene-α-d1
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The room-temperature vapor phase overtone spectrum of toluene-α-d1 has been recorded in the CH stretching regions corresponding to ΔυCH = 2-7. The vibrational overtone spectra are recorded by conventional near-infrared spectroscopy a
- Kjaergaard, Henrik G.,Turnbull, David M.,Henry, Bryan R.
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Read Online
- Confirmation of a Large Kinetic Isotop Effect in the Low-Temperature Matrix Reaction of Diphenylcarbene with Toluene
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The reaction of diphenylcarbene with toluene was investigated as a function of temperature.The distribution of products formed in this reaction and the kinetic isotope effects observed (>100 at 77 K) are consistent with a triplet carbene mechanism over a
- Savino, T. G.,Soundararajan, N.,Platz, M. S.
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Read Online
- Preliminary investigations on the catalytic hydrogenation of polycyclic aromatic hydrocarbons via WGSR
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The water-gas shift reaction (WGSR) is a crucial reaction in the direct liquefaction of lignite in a syngas (CO + H2) system. In this study, anthracene was utilized as a polycyclic model compound of lignite, to which hydrogen is donated by the H2/D2 produced from CO and H2O/D2O via the WGSR. The results show that the model compound of the polycyclic aromatic hydrocarbon in coal (anthracene) undergoes partial cracking and polycondensation under non-hydrogen-donor conditions at 400 °C. In addition, WGSR catalyzed by NiO can generate hydrogen for the hydrogenation of anthracene. Comparing the mass spectra of deuterated products with those of conventional hydrogenation products by isotope labeling, the alkyl side chain positions of toluene, 1,4-xylene, methylnaphthalene, 1,1-diphenylethylene, methylanthracene and other compounds are prone to deuteration, enabling speculation of the main hydrogenation route of anthracene, which provides theoretical support for the catalytic hydrogenation in direct liquefaction of lignite in a syngas (CO + H2) system.
- Chen, Dabo,Gu, Jiale,Huang, Sheng,Li, Huan,Wu, Shiyong,Wu, Youqing
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- Method for preparing deuterated compound through decarboxylation and deuteration of carboxylic acid
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The invention relates to a method for preparing a deuterated compound through decarboxylation and deuteration of carboxylic acid. According to the method, a carboxylic acid compound is used as a raw material, hydrogen atoms of carboxylate radicals are exc
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Paragraph 0056; 0058-0059
(2021/06/13)
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- Methane Generation and Reductive Debromination of Benzylic Position by Reconstituted Myoglobin Containing Nickel Tetradehydrocorrin as a Model of Methyl-coenzyme M Reductase
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Methyl-coenzyme M reductase (MCR), which contains the nickel hydrocorphinoid cofactor F430, is responsible for biological methane generation under anaerobic conditions via a reaction mechanism which has not been completely elucidated. In this work, myoglobin reconstituted with an artificial cofactor, nickel(I) tetradehydrocorrin (NiI(TDHC)), is used as a protein-based functional model for MCR. The reconstituted protein, rMb(NiI(TDHC)), is found to react with methyl donors such as methyl p-toluenesulfonate and trimethylsulfonium iodide with methane evolution observed in aqueous media containing dithionite. Moreover, rMb(NiI(TDHC)) is found to convert benzyl bromide derivatives to reductively debrominated products without homocoupling products. The reactivity increases in the order of primary > secondary > tertiary benzylic carbons, indicating steric effects on the reaction of the nickel center with the benzylic carbon in the initial step. In addition, Hammett plots using a series of para-substituted benzyl bromides exhibit enhancement of the reactivity with introduction of electron-withdrawing substituents, as shown by the positive slope against polar substituent constants. These results suggest a nucleophilic SN2-type reaction of the Ni(I) species with the benzylic carbon to provide an organonickel species as an intermediate. The reaction in D2O buffer at pD 7.0 causes a complete isotope shift of the product by +1 mass unit, supporting our proposal that protonation of the organonickel intermediate occurs during product formation. Although the turnover numbers are limited due to inactivation of the cofactor by side reactions, the present findings will contribute to elucidating the reaction mechanism of MCR-catalyzed methane generation from activated methyl sources and dehalogenation.
- Hayashi, Takashi,Miyazaki, Yuta,Oohora, Koji
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supporting information
p. 11995 - 12004
(2020/09/15)
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- Reversible Formation of Alkyl Radicals at [Fe4S4] Clusters and Its Implications for Selectivity in Radical SAM Enzymes
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All kingdoms of life use the transient 5′-deoxyadenosyl radical (5′-dAdoa ) to initiate a wide range of difficult chemical reactions. Because of its high reactivity, the 5′-dAdo?must be generated in a controlled manner to abstract a specific H atom and avoid unproductive reactions. In radical S-Adenosylmethionine (SAM) enzymes, the 5′-dAdo?is formed upon reduction of SAM by an [Fe4S4] cluster. An organometallic precursor featuring an Fe-C bond between the [Fe4S4] cluster and the 5′-dAdo group was recently characterized and shown to be competent for substrate radical generation, presumably via Fe-C bond homolysis. Such reactivity is without precedent for Fe-S clusters. Here, we show that synthetic [Fe4S4]-Alkyl clusters undergo Fe-C bond homolysis when the alkylated Fe site has a suitable coordination number, thereby providing support for the intermediacy of organometallic species in radical SAM enzymes. Addition of pyridine donors to [(IMes)3Fe4S4-R]+ clusters (R = alkyl or benzyl; IMes = 1,3-dimesitylimidazol-2-ylidene) generates Ra , ultimately forming R-R coupled hydrocarbons. This process is facile at room temperature and allows for the generation of highly reactive radicals including primary carbon radicals. Mechanistic studies, including use of the 5-hexenyl radical clock, demonstrate that Fe-C bond homolysis occurs reversibly. Using these experimental insights and kinetic simulations, we evaluate the circumstances in which an organometallic intermediate can direct the 5′-dAdo?toward productive H-Atom abstraction. Our findings demonstrate that reversible homolysis of even weak M-C bonds is a feasible protective mechanism for the 5′-dAdo?that can allow selective X-H bond activation in both radical SAM and adenosylcobalamin enzymes.
- Brown, Alexandra C.,Suess, Daniel L. M.
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supporting information
p. 14240 - 14248
(2020/09/15)
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- Photocatalytic halohydrocarbon dehalogenation conversion method
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The invention provides a photocatalytic halohydrocarbon dehalogenation conversion method which comprises the following steps: adding a photocatalyst quantum dot/rod into a solvent to obtain a solutionA; adding halohydrocarbon and an electronic sacrificial body into the solution A to obtain a solution B; utilizing a light source to irradiate the solution B and catalyzing the solution B to performhalohydrocarbon dehalogenation conversion. According to the photocatalytic halohydrocarbon dehalogenation conversion method disclosed by the invention, a nano quantum dot and a nano quantum rod are applied to dehalogenation conversion reaction of alkyl halide, alkenyl halide and alkyne halide for the first time; the reaction conditions are moderate, visible light is utilized as driving energy, a product is hydrocarbon compound, and the whole process has the advantages of environmental protection, conciseness and high efficiency. In addition, higher hydrocarbon of carbon chain growth can be generated after dehalogenation reaction, so that the method has potential application in preparation of higher hydrocarbon. According to the method disclosed by the invention, halohydrocarbon dehalogenation conversion and deuteration marking processes are jointly performed; hydrocarbon deuteration marking can be finished when a halohydrocarbon dehalogenation process is finished. The invention furtherprovides a method for performing deuteration marking on hydrocarbon.
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Paragraph 0105; 0106
(2019/04/02)
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- C(sp3)-H Bond Arylation and Amidation of Si-Bound Methyl Group via Directing Group Strategy
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Silylmethyl functionalization provides a general and efficient access to diverse organosilanes. The traditional methods for silylmethyl functionalization often involved silylmethylmetals or silylmethylhalides. In recent years, a C-H activation strategy has become one of the most attractive alternatives in organic synthesis. We envisioned that the attachment of a coordinating group at silicon of methylsilanes provides the opportunity to modify the silylmethyl group via directed C-H bond functionalization. However, despite employment of silicon tethers bearing a directing group (DG) for C(sp2)-H functionalization has been well established due to the fact that the silicon tethers are easily installable and removable/modifiable, applying this concept toward C(sp3)-H functionalization remains underdeveloped. Herein, we successfully develop IrIII/RhIII-catalyzed C-H bond arylation/amidation of silyl methyl group by using directing group strategy, which constitutes the most powerful access to benzylsilanes and amino-substituted silanes. Moreover, we demonstrated that the pyridine directing group on silicon atom can be easily removed, and the starting materials can also be efficiently recovered, which are different from those of pyridine-directed C-H functionalization of C-bound methyl group.
- Han, Jie-Lian,Qin, Ying,Zhao, Dongbing
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p. 6020 - 6026
(2019/06/25)
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- Dramatic Synergy in CoPt Nanocatalysts Stabilized by "click" Dendrimers for Evolution of Hydrogen from Hydrolysis of Ammonia Borane
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Hydrolysis of ammonia borane (AB) is a very convenient source of H2, but this reaction needs catalytic activation to become practical under ambient conditions. Here this reaction is catalyzed by bimetallic late transition-metal nanoparticles (N
- Wang, Qi,Fu, Fangyu,Yang, Sha,Martinez Moro, Marta,Ramirez, Maria De Los Angeles,Moya, Sergio,Salmon, Lionel,Ruiz, Jaime,Astruc, Didier
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p. 1110 - 1119
(2019/01/21)
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- Hydrogenation of Benzonitrile over Supported Pd Catalysts: Kinetic and Mechanistic Insight
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The liquid phase hydrogenation of benzonitrile over a 5 wt % Pd/C catalyst using a stirred autoclave is investigated. The reaction conforms to a consecutive reaction sequence: first benzonitrile is hydrogenated to produce benzylamine, which subsequently u
- McAllister, Mairi I.,Boulho, Cédric,Gilpin, Lauren F.,McMillan, Liam,Brennan, Colin,Lennon, David
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p. 977 - 989
(2019/04/25)
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- Method for constructing carbon-hydrogen bond by catalyzing alcohol dehydroxylation with palladium/platinum
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The invention discloses a method for constructing a carbon-hydrogen (deuterium) bond. The method comprises the following step: in the presence of a palladium/platinum catalyst and aryl halide, an alcohol hydroxyl group of an alcohol and hydrogen (deuterium) gas is replaced by hydrogen (deuterium) to construct the carbon-hydrogen (deuterium) bond. According to the method, the palladium/platinum catalyst is used as a catalyst, the green hydrogen (deuterium) gas is used as a hydrogen (deuterium) source, efficient alcohol dehydroxylation is performed at room temperature to construct the carbon-hydrogen (deuterium) bond, and the method is particularly suitable for constructing the carbon-deuterium bond and can be widely applied to synthesis of deuterated drugs.
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Paragraph 0114-0117
(2019/12/25)
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- Probing Substrate Diffusion in Interstitial MOF Chemistry with Kinetic Isotope Effects
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Metal–organic frameworks (MOFs) have garnered substantial interest as platforms for site-isolated catalysis. Efficient diffusion of small-molecule substrates to interstitial lattice-confined catalyst sites is critical to leveraging unique opportunities of
- Wang, Chen-Hao,Das, Anuvab,Gao, Wen-Yang,Powers, David C.
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supporting information
p. 3676 - 3681
(2018/03/06)
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- An Additive-Free, Base-Catalyzed Protodesilylation of Organosilanes
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We report an additive-free, base-catalyzed C-, N-, O-, and S-Si bond cleavage of various organosilanes in mild conditions. The novel catalyst system exhibits high efficiency and good functional group compatibility, providing the corresponding products in good to excellent yields with low catalyst loadings. Overall, this transition-metal-free process may offer a convenient and general alternative to current employing excess bases, strong acids, or metal-catalyzed systems for the protodesilylation of organosilanes.
- Yao, Wubing,Li, Rongrong,Jiang, Huajiang,Han, Deman
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p. 2250 - 2255
(2018/02/23)
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- Homocoupling of iodoarenes and bromoalkanes using photoredox gold catalysis: A light enabled Au(III) reductive elimination
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The formation of homocoupled alkane byproducts have been identified in the reduction of bromoalkanes via photoredox gold catalysis with dimeric Au(I) complexes. This prompted further investigation into the mechanism of formation of these byproducts and the diversity of C-X bonds amenable to this transformation. Examples were found when considering bromoalkanes while a wide variety of iodoarenes underwent this process in good to excellent yields. The light enabled homocoupling of iodoarenes made possible by photoredox gold catalysis is reported.
- Tran, Huy,McCallum, Terry,Morin, Mathieu,Barriault, Louis
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supporting information
p. 4308 - 4311
(2016/09/09)
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- Free radical mechanism investigation of the side-chain alkylation of toluene with methanol on basic zeolites X
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The side-chain alkylation of toluene represents a novel, environmentally friendly, and low cost route for the production of styrene. However, the yield of styrene produced in this way is currently low, and the mechanism responsible for the side-chain alky
- Chen, Huanhui,Li, Xiaoci,Zhao, Guoqing,Gu, Hongbo,Zhu, Zhirong
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p. 1726 - 1732
(2015/10/19)
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- Kinetics and mechanism of the reaction of benzyl bromide with copper in dimethylacetamide in the presence of oxygen
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The reaction of copper metal with benzyl bromide in dimethylacetamide in the presence of oxygen has been studied. Oxidative dissolution of copper follows the single-electron transfer mechanism with formation of benzaldehyde, benzyl alcohols, and copper(II
- Egorov,Matyukhova
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p. 1667 - 1675
(2015/01/09)
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- Nonhydrolytic synthesis of silanols by the hydrogenolysis of benzyloxysilanes
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The hydrogenolysis of benzyloxysilanes was smoothly catalyzed by Pd/C in THF to give corresponding silanols under nonhydrolytic conditions. The reaction proved to be applicable to various benzyloxysilanes giving silanemonools, diol, and triol.
- Igarashi, Masayasu,Matsumoto, Tomohiro,Sato, Kazuhiko,Ando, Wataru,Shimada, Shigeru
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p. 429 - 431
(2014/04/17)
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- Homo- and hetero-oxidative coupling of benzyl anions
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The regioselective benzylic metalation of substituted toluenes using BuLi/KO-t-Bu/TMP(H) (LiNK metalation conditions) with subsequent in situ oxidative C-C coupling has been developed for the facile generation of 1,2-diarylethanes. A range of oxidants can be used for the oxidative coupling step, with 1,2-dibromoethane proving optimal. Heterocouplings can be achieved starting from a mixture of two different toluenes with a bias toward cross coupling achievable by using a 2-fold excess of one toluene starting material. The utility of this approach is illustrated by the synthesis of several biologically active natural products. A distinct advantage is that the synthetic steps typically required to preactivate the coupling substrates are eliminated and no transition metal is required to facilitate the C-C bond formation.
- Blangetti, Marco,Fleming, Patricia,O'Shea, Donal F.
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experimental part
p. 2870 - 2877
(2012/04/23)
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- Kinetics and mechanism of nickel reaction with benzyl bromide in dimethylformamide
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Abstarct: The reaction of nickel with benzyl bromide in DMF has been studied. The reaction intermediates were investigated by different methods and the kinetic and thermodynamic parameters were determined. The reaction of benzyl bromide with nickel was shown to occur on the metal surface by the Langmuir-Hinshelwood scheme, with the formation of benzyl radicals which are recombined and isomerized in solution to form 1,2-diphenylethane and trace amounts of 4.4'-dimethylbiphenyl.
- Egorov,Matyukhova,Kocherova,Novikova,Anisimov
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body text
p. 444 - 452
(2009/06/28)
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- SmI2/H2O/amine promoted reductive cleavage of benzyl-heteroatom bonds: optimization and mechanism
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The SmI2/H2O/pyrrolidine mediated cleavage of benzylic alcohols and benzyl groups was studied and found to be a viable alternative to the Birch reduction yielding the corresponding deoxygenated product in excellent yield. The reaction has been investigated by kinetic methods, and a mechanism involving a pre-complexation of the alcohol to SmI2 followed by an amine mediated electron transfer and subsequent bond cleavage and transfer of a second electron and proton to yield the toluene product has been proposed. The reaction is strongly inhibited at higher concentrations of water, indicating that it proceeds via an inner-sphere electron transfer from samarium(II) to the benzyl group, and excess of water prevents coordination of benzyl alcohol to samarium.
- Ankner, Tobias,Hilmersson, G?ran
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experimental part
p. 10856 - 10862
(2010/02/28)
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- Intermolecular insertion of an N,N-heterocycIic carbene into a nonacidic C-H bond: Kinetics, mechanism and catalysis by (K-HMDS)2 (HMDS = Hexamethyldisilazide)
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The reaction of 2-[13C]-1-ethyl-3-isopropyl-3,4,5,6- tetrahydropyrimidin-1-ium hexafluorophosphate ([13C 1]-1-PF6) with a slight excess (1.03 equiv) of dimeric potassium hexamethyldisilazide ("(K-HMDS)2/su
- Lloyd-Jones, Guy C.,Alder, Roger W.,Owen-Smith, Gareth J. J.
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p. 5361 - 5375
(2008/02/13)
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- Kinetics and mechanism of the reaction of benzyl bromide with copper in hexamethylphosphoramide
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The reaction of copper with benzyl bromides in hexamethylphosphoramide has been studied. The kinetic and thermodynamic parameters of the reaction have been obtained. Hammett plots of log (script k sign/script k sign°) vs the substituent constant σ gave good correlations (ρ = 0.15, S ρ = 0.02, r = 0.954). The structure of the organic group has little effect on the rate of reaction of benzyl bromide with copper. In the absence of atmospheric oxygen, the oxidative dissolution of copper occurred by the mechanism of single-electron transfer with the formation of 1,2-diphenylethane and copper(I) complexes. The stereochemistry and intermediates compound was also investigated. The reaction mechanism is discussed.
- Egorov, Anatoly M.,Matyukhova, Svetlana A.,Anisimov, Alexander V.
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p. 296 - 305
(2007/10/03)
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- Kinetics and mechanism of the reaction of benzyl bromide with titanium in dimethylformamide
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The reaction of titanium with benzyl bromide in dimethylformamide was studied. No reaction occurs in the presence of atmospheric oxygen. Under oxygen-free conditions, the oxidative dissolution of titanium occurs by the mechanism of one-electron transfer with the formation of 1,2-diphenylethane and Ti(IV) complexes. The kinetic and thermodynamic parameters of the process were determined. The reaction mechanism was discussed. 2005 Pleiades Publishing, Inc.
- Egorov,Matyukhova,Uvarova,Anisimov
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p. 1445 - 1451
(2008/02/03)
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- Kinetics and mechanism of reaction of benzyl bromide with copper in dimethylacetamide
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The reaction of copper with various benzyl bromides in dimethylacetamide was studied. In the absence of atmospheric oxygen, oxidative dissolution of copper occurred by the mechanism of single electron transfer with the formation of 1,2-diphenylethane and
- Egorov, Anatoly M.,Matyukhova, Svetlana A.,Anisimov, Alexander V.
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p. 456 - 461
(2007/10/03)
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- Isotope Effects and Hydrogen Exchange Mechanism in Compounds Having Labile Aliphatic C-H Bonds in Basic Liquid Ammonia Solutions
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Specific features of the stepwise hydrogen exchange mechanism and transition state structure in the systems acetophenone-liquid ammonia in the absence of foreign compounds and in the presence of bases and toluene-liquid ammonia in the presence of potassium amide were studied in terms of an approach based primary and secondary kinetic isotope effects of the substrate and the solvent. The mechanisms of reactions involving acetophenone and toluene were compared. In the first case, an elementary act of CH-acid ionization is contributed to a small extent by diffusion-controlled separation of the carbanion and ammonia molecule, hydrogen exchange in toluene is characterized by complete absence of the internal ion pair return effect. The ratio k dNH3/kTNH3 for hydrogen exchange in acetophenone tends to decrease on addition of bases (with simultaneous increase in its rate), which may be explained by formation of an adduct via interaction between the unshared electron pair on the heteroatom in the base molecule and the carbonyl carbon atom. The anomalous temperature dependence of k DNH3/kTNH3 for hydrogen exchange in toluene is interpreted as a result of contribution of side metalation of the C-H bond by potassium amide. The change in the solvent protophilicity due to replacement of the "light" solvent by deuterated one differently affects the kinetics and mechanism of hydrogen exchange in acetophenone and toluene. Measurements of the α-deuterium effect gave information on the mode of angular deformation of C-D bonds in the methyl group of toluene in the hydrogen exchange transition state.
- Tupitsyn,Zatsepina
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p. 358 - 370
(2007/10/03)
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- Inter- and intramolecular experimental and calculated equilibrium isotope effects for (silox)2((t)Bu3SiND)TiR + RH (silox = (t)Bu3SiO): Inferred kinetic isotope effects for RH/D addition to transient (silox)2Ti
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Intermolecular equilibrium isotope effects (EIEs) were measured (26.5 °C) and calculated for (silox)2((t)Bu3SiND)TiR(D) (1-ND-R(D)) + R(H)H ? (silox)2((t)Bu3SiNH)TiR(H) (1-R(H)) + R(D)D: R(H)H/R(D)D = CH4/
- Slaughter, Legrande M.,Wolczanski, Peter T.,Klinckman, Thomas R.,Cundari, Thomas R.
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p. 7953 - 7975
(2007/10/03)
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- Hydrodehalogenation of 1,1-dibromocyclopropanes by Grignard reagents promoted by titanium compounds
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1,1-Dibromocyclopropanes are converted into the corresponding monobromocyclopropanes (as mixtures of stereoisomers where appropriate) by reaction with 1.0-1.3 mol equiv. of ethylmagnesium bromide and 2-10 mol% titanium isopropoxide for 90%). With ethylmagnesium bromide, the reaction occurs very slowly in the absence of catalyst; with methylmagnesium bromide, the reaction does occur in the absence of catalyst, but is only slightly promoted in the presence of titanium isopropoxide. Reactions with a number of other Grignard reagents are also discussed. In the case of phenethylmagnesium bromide, the major product containing the phenethyl-group is ethylbenzene, together with small amounts of styrene and ethyl 4-phenyl-2-butyl ether, a product of trapping of the solvent, ether. In other cases, relatively large amounts of a diether, formally derived by hydrogen ion adjacent to the ether oxygen followed by dimerisation, are isolated. No products were identified incorporating the cyclopropane and either the Grignard alkyl group or the solvent. Labelling studies indicate that the hydrogen introduced into the cyclopropane is not derived from either the α- or β-positions of the Grignard reagent. When the reduction is carried out with phenethylmagnesium bromide in d8-tetrahydrofuran both monobromides contain deuterium.
- Dulayymi, Juma'a R. Al,Baird, Mark S.,Bolesov, Ivan G.,Nizovtsev, Alexey V.,Tverezovsky, Viacheslav V.
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p. 1603 - 1618
(2007/10/03)
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- C-O bond homolysis in a tungsten alkoxide: The mechanism of alcohol deoxygenation by WCl2(PMe3)4 and WH2Cl2(PMe3)4
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Reactions of alcohols with WCl2(PMe3)4 (1) or WH2Cl2(PMe3)4 (2) yield W(O)Cl2(PMe3)3 (3), PMe3, and hydrocarbons. Cyclopropanemethanol is deoxygenated to give 1-butene and a trace of trans-2-butene as the organic products; benzyl alcohol yields toluene and bibenzyl. These products indicate the intermediacy of organic radicals. Benzyl radicals in the reaction of 1 with PhCH2OH can be trapped by added 2 or by 9,10-dihydroanthracene (DHA), leading to increased yields of toluene vs bibenzyl. With WD2Cl2(PMe3)4 (2-d2) or DHA-d12, PhCH2D is formed. The reaction of methanol with 1 proceeds similarly in the presence of DHA, forming 3 and methane. Kinetic studies on the reaction of 1 with benzyl alcohol indicate that the reaction proceeds via alkoxide intermediates. A mechanism involving homolysis of the C-O bond in an alkoxide intermediate is suggested by these results. The thermodynamics of this unusual transformation are discussed.
- Crevier, Thomas J.,Mayer, James M.
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p. 8485 - 8491
(2007/10/03)
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- Reaction of 1,2-Diphenylethane with D2
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The reaction of 1,2-diphenylethane (DPE) with D2 (2000 psi) was studied at 450 deg C.The results of GC/MS and NMR analysis of reaction products and of products from reactions of 1,2-diphenylethane-1,1-d2, 1,2-di(phenyl-d5)ethane, and 1,2,3,4-tetraphenylbutane confirm a mechanistic scheme in which the main process for introduction of D is the reaction of 1,2-diphenylethyl radical with D2.This reaction, though energetically uphill, competes with termination processes because of the high concentration of D2 relative to that of radical species.The reaction generates D atoms which attack aromatic ring positions to give substitution for both H and alkyl substituents.Evidence is provided for D and H atom transfer between aliphatic positions in DPE in the presence of either N2 or H2 and between aromatic positions only when provoked by H2 or D2.Only a small amount of exchange between aromatic and aliphatic positions is observed under any conditions.The attack of D atoms at H-carrying aromatic positions makes H atoms available for transfer to other aromatic positions.The process results in a D2-provoked generation of benzene-d0.Mechanistic alternatives for these and other processes are discussed.
- Guthrie, Robert D.,Shi, Buchang,Rajagopal, Venkatsubramanian,Ramakrishnan, Sreekumar,Davis, Burtron H.
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p. 7426 - 7432
(2007/10/02)
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- Cadmium Chloride-Magnesium-Water: A New System For Reduction of Various Organic Functionalities
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Cadmium chloride-magnesium-THF-water efficiently reduced aldehydes and ketones to their corresponding alcohols, epoxide to mono-alcohol, benzyl halide to toluene, acid chloride to aldehyde and hydrolyzed thioketals to corresponding ketones. Key words: Cadmium chloride-magnesium-THF-H2O, reductions.
- Bordoloi, Manobjyoti
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p. 1681 - 1684
(2007/10/02)
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- Gas-Phase Proton Transfer from Toluenes to Benzyl Anions
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Gas-phase proton-transfer kinetics of PhCH2(1-) + ArCH3 -> ArCH2(1-) + PhCH3 were studied for reactions having ΔH0rxn = 0 to -20 kcal/mol.These reactions are very slow in the absence of thermodynamic driving force; their reaction efficiencies range from 0.004 to 0.7.RRKM theory was applied to obtain energy differences between the proton-transfer transition state and the loose orbiting transition state from reaction efficiencies.Marcus theory provides a general model for a rate-equilibrium relationship with a constant intrinsic energy barrier of 7 kcal/mol forthe degenerate proton transfer from toluene to benzyl anion.The barrier is inferred from an RRKM fit to the energy difference of -5 kcal/mol between the proton-transfer transition state and the energy of the reactants and an estimated -12 kcal/mol for the energy of the collision complex relative to the reactants.In the reaction involving 3-nitrotoluene, electron transfer, which is some 11-12 kcal/mol less favorable than proton transfer, dominates almost exclusively.
- Han, Chau-Chung,Brauman, John I.
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p. 6491 - 6496
(2007/10/02)
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- Primary and Secondary Kinetic Hydrogen Isotope Effects in the Solution and Gas Phase Decomposition of t-Alkoxides
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Primary and secondary kinetic hydrogen isotope effects (k.i.e.s) in the elimination of toluene from the alkoxide of 1,2,3-triphenylpropane-2-ol have been determined and are consistent with rate limiting proton transfer in gas phase reaction and with rate limiting carbon-carbon bond cleavage in reaction in dimethyl sulphoxide (DMSO) solution.
- Ibrahim, Sani,Watt, C. Ian F.,Wilson, John M.,Moore, Colin
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p. 161 - 163
(2007/10/02)
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- Side Chain Hydroxylation of Aromatic Hydrocarbons by Fungi. Part 2. Isotope Effects and Mechanism
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The benzylic hydroxylation of ethylbenzene, p-diethylbenzene, tetralin, indane, and toluene by the fungi Mortierella isabellina, Cunninghamella echinulata, and Helminthosporium species has been investigated by the use of deuterium-labelled substrates.An i
- Holland, Herbert L.,Brown, Frances M.,Munoz, Benito,Ninnis, Ronald W.
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p. 1557 - 1564
(2007/10/02)
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- CH ACIDITY OF SUBSTITUTED CYCLOALKANES. I. KINETIC ACIDITY OF PHENYLCYCLOALKANES
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The kinetic acidities of phenylcycloalkanes were determined in a solution of lithium cyclohexylamide in cyclohexylamine.The obtained values are compared with the analogous values for cycloalkanes and with the heats of hydrogenation of methylenecycloalkanes.The introduction of the phenyl substituent increases the proton mobility of the hydrogen in the cycloalkanes.A relation was established between the kinetic acidity of the phenylcycloalkanes and the strain in the alkane rings of their carbanions.
- Zharova, N. G.,Shapiro, I. O.,Shatenshtein, A. I.
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p. 211 - 214
(2007/10/02)
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- Primary and Secondary Kinetic Deuterium Isotope Effects and Transition-State Structures for Benzylic Chlorination and Bromination of Toluene
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As a chemical model for benzylic hydroxylations effected by cytochrome P-450 enzymes, the chlorination of PhCH3, PhCH2D, PhCHD2, and PhCD3 in a two-phase system of hypochlorite/CH2Cl2 with a phase-transfer catalyst has been investigated.On the basis of th
- Hanzlik, Robert P.,Schaefer, Angela R.,Moon, Joseph B.,Judson, Charles M.
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p. 4926 - 4930
(2007/10/02)
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- Ether cleavage by activated metals II.* Cleavage of allyl and benzyl ethers by activated magnesium
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Activated magnesium (prepared by reduction of magnesium halides with potassium) reacts with allyl and benzyl ethers to give the corresponding allyl or benzyl magnesium compounds.
- Bartmann, Ekkehard
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- Intramolecular Kinetic Deuterium Isotope Effects on Microsomal Hydroxylation and Chemical Chlorination of Toluene-α-d1 and Toluene-α,α-d2
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Deuterated toluenes PhCH2D and PhCHD2 were synthesized and subjected separately to microsomal hydroxylation in vitro.Mass spectral analysis of the resulting benzyl alcohols indicated substatial excess retention of deuterium, a consequence of the combined
- Hanzlik, Robert P.,Hogberg, Kerstin,Moon, Joseph B.,Judson, Charles M.
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p. 7164 - 7167
(2007/10/02)
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- Occurrence of Electron Transfer in the Reduction of Organic Halides by LiAlH4 and AlH3
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A variety of methods have been utilized to detect the occurrence of a single electron transfer pathway in the reduction of alkyl halides by LiAlH4 and AlH3, i.e., (1) product studies of reduction of cyclizable alkyl halides containing the 5-hexenyl group, (2) trapping of intermediate radicals by dicyclohexylphosphine and other trapping agents, (3) direct EPR observation of the trityl radical in the reduction of trityl bromide, and (4) stereochemical studies of the reduction of secondary halides by lithium aluminum deuteride.The extent of electron transfer was found to be a function of the solvent, the substrate, the leaving group, and the hydride reagent.For alkyl iodides, and to a lesser extent bromides, electron transfer was found to be the major reaction pathway; however, no evidence for electron transfer was found for the corresponding chlorides or tosylates.Reduction of (+)-2-octyl iodide by LiAlD4 was found to be much less stereospecific than the corresponding reduction of bromide, chloride, or tosylate, indicating intermediate radical formation in the reduction of the secondary iodide.
- Ashby, E. C.,DePriest, R. N.,Goel, A. B.,Wenderoth, Bernd,Pham, Tung N.
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p. 3545 - 3556
(2007/10/02)
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- Reductive Deamination of Primary Amines
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1-Alkyl-1,2-dihydropyridines thermolyse to complex mixtures, but 1-alkyl-2,3,5,6-tetraphenyl-1,4-dihydropyridines (prepared from the amine and 2,3,5,6-tetraphenylpyrylium salts followed by NaBH4) give alkanes smoothly at ca.200 deg C.Thermolysis of 1-benzyl-2-deuterio-2,4,6-triphenyl-1,2-dihydropyridine gives ω-monodeuteriotoluene (as shown by 2H n.m.r. spectroscopy) indicating a radical mechanism.
- Katritzky, Alan R.,Horvath, Karoly,Plau, Bernard
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p. 2554 - 2560
(2007/10/02)
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