- Intramolecular interactions in ortho-methoxyalkylphenylboronic acids and their catechol esters
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(Graph Presented) Catechol esters of ortho-methoxyalkylphenylboronic acids have been synthesized and characterized by 17O NMR spectroscopy. The results were compared with the data for the parent acids. The influence of intramolecular and intermolecular hydrogen bonds on the properties of the boronic acids has been discussed. The 17O NMR data for the boronic esters proved that there are no O → B interactions in the investigated compounds. This fact is connected with weak Lewis acidity of the parent acids and their low sugars' receptors activity. Crystal structure of ortho -methoxyphenylboronic acid catechol ester was determined.
- Adamczyk-Wozniak, Agnieszka,Borys, Krzysztof M.,Czerwinska, Karolina,Gierczyk, Blazej,Jakubczyk, Michal,Madura, Izabela D.,Sporzynski, Andrzej,Tomecka, Ewelina
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Read Online
- Oxidative 1,2-Difunctionalization of Ethylene via Gold-Catalyzed Oxyarylation
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Under the conditions of oxidative gold catalysis, exposure of ethylene to aryl silanes and alcohols generates products of 1,2-oxyarylation. This provides a rare example of a process that allows catalytic differential 1,2-difunctionalization of this feedstock chemical.
- Harper, Matthew J.,Emmett, Edward J.,Bower, John F.,Russell, Christopher A.
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supporting information
p. 12386 - 12389
(2017/09/22)
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- Photoredox-Assisted Reductive Cross-Coupling: Mechanistic Insight into Catalytic Aryl-Alkyl Cross-Couplings
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Here, we describe a photoredox-assisted catalytic system for the direct reductive coupling of two carbon electrophiles. Recent advances have shown that nickel catalysts are active toward the coupling of sp3-carbon electrophiles and that well-controlled, light-driven coupling systems are possible. Our system, composed of a nickel catalyst, an iridium photosensitizer, and an amine electron donor, is capable of coupling halocarbons with high yields. Spectroscopic studies support a mechanism where under visible light irradiation the Ir photosensitizer in conjunction with triethanolamine are capable of reducing a nickel catalyst and activating the catalyst toward cross-coupling of carbon electrophiles. The synthetic methodology developed here operates at low 1 mol % catalyst and photosensitizer loadings. The catalytic system also operates without reaction additives such as inorganic salts or bases. A general and effective sp2-sp3 cross-coupling scheme has been achieved that exhibits tolerance to a wide array of functional groups.
- Paul, Avishek,Smith, Mark D.,Vannucci, Aaron K.
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p. 1996 - 2003
(2017/02/26)
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- Synthetic method for medical intermediate methyl phenethyl ether of metoprolol
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The invention discloses a synthetic method for a medical intermediate methyl phenethyl ether of metoprolol. The synthetic method includes the following steps that 1.3 mol of phenethyl alcohol (2) and 1.5-1.7 mol of sodium sulfite are added into a reaction vessel provided with a stirrer, a thermometer, a reflux condenser and a dropping funnel, the stirring speed is controlled to be 130-160 rpm, and the temperature of the solution is increased to 80-85 DEG C; 1.3-1.5 mol of methyl-trimethylamine phosphoric acid is dropwise added, and continuous reacting is carried out for 3-4 h after the methyl-trimethylamine phosphoric acid is added; 300 ml of potassium chloride solutions are added, the temperature of the solution is reduced to 3-5 DEG C, the mixture is extracted with cyclohexane 3-5 times, an extracting solution is dehydrated through a dehydrating agent, the cyclohexane is evaporated, reduced pressure distillation is carried out, and the fractions obtained at the temperature of 65-75 DEG C are collected; recrystallization is carried out in propionitrile, and the methyl phenethyl ether (1) is obtained; the mass percent of the potassium chloride solutions ranges from 15% to 20%, and the mass percent of the cyclohexane ranges from 80% to 85%.
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Paragraph 0015; 0016
(2017/03/28)
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- Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation
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The nucleophilic addition of methanol and other alcohols to 1,1-diphenylethylene (1) and styrene (6) into the Markovnikov- and anti-Markovnikov-type products was selectively achieved with 1-(N,N-dimethylamino)pyrene (Py) and 1,7-dicyanoperylene-3,4:9,10-tetracarboxylic acid bisimide (PDI) as photoredox catalysts. The regioselectivity was controlled by the photocatalyst. For the reductive mode towards the Markovnikov-type regioselectivity, Py was applied as photocatalyst and triethylamine as electron shuttle. This approach was also used for intramolecular additions. For the oxidative mode towards the anti-Markovnikov-type regioselectivety, PDI was applied together with Ph-SH as additive. Photocatalytic additions of a variety of alcohols gave the corresponding products in good to excellent yields. The proposed photocatalytic electron transfer mechanism was supported by detection of the PDI radical anion as key intermediate and by comparison of two intramolecular reactions with different electron density. Representative mesoflow reactor experiments allowed to significantly shorten the irradiation times and to use sunlight as "green"light source.
- Weiser, Martin,Hermann, Sergej,Penner, Alexander,Wagenknecht, Hans-Achim
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p. 568 - 575
(2015/06/08)
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- METHOD FOR PRODUCING ETHER COMPOUND
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An object of the present invention is to provide a method for producing an ether compound easily in a small number of steps at lower costs in high yields. The present invention relates to a method in which the ether compound represented by the general formula (1) is produced by reacting the specific carbonyl compound specified in the general formula (2) and the specific dialkoxy compound specified in the general formula (3) with hydrogen in the presence of a hydrogenation catalyst and an acidic substance to perform hydrogenation.
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Paragraph 0141
(2015/01/18)
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- Iron-catalyzed N-alkylation using π-activated ethers as electrophiles
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A new method for the synthesis of diverse N-alkylation compounds was developed via an iron-catalyzed etheric Csp3-O cleavage with the C-N bond formation in the reaction of π-activated ethers with various nitrogen-based nucleophiles. In addition, the mechanism of this reaction was investigated. The Royal Society of Chemistry 2013.
- Fan, Xiaohui,Fu, Lin-An,Li, Na,Lv, Hao,Cui, Xiao-Meng,Qi, Yuan
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supporting information
p. 2147 - 2153
(2013/04/10)
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- Fe-promoted cross coupling of homobenzylic methyl ethers with Grignard reagents via sp3 C-O bond cleavage
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The first iron-catalyzed formal cross coupling of homobenzylic methyl ethers with alkyl Grignard reagents is realized. The reaction is proposed to proceed through a sequence of dehydroalkoxylation to form the vinyl-intermediate, followed by Fe-catalyzed selective carbometalation to form a benzylic Grignard reagent.
- Luo, Shuang,Yu, Da-Gang,Zhu, Ru-Yi,Wang, Xin,Wang, Lei,Shi, Zhang-Jie
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supporting information
p. 7794 - 7796
(2013/09/02)
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- Efficient palladium-catalyzed C-O hydrogenolysis of benzylic alcohols and aromatic ketones with polymethylhydrosiloxane
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A simple method has been developed for the reductive deoxygenation of aromatic ketones and benzylic alcohols in the presence of polymethylhydrosiloxane (PMHS). The reductive deoxygenation of aromatic ketones and benzylic alcohols, including secondary alcohols, to the corresponding methylene hydrocarbons has been achieved in good to excellent yields using palladium chloride (PdCl2) as catalyst and PMHS as hydride source. Such deoxygenations were successfully with aryl alkyl ketones and diaryl ketones, as exemplified by the reductive deoxygenation of acetophenone and benzopheneone, respectively. The corresponding benzylic alcohols and secondary alcohol analogues could also be converted into their respective methylene hydrocarbons by the PdCl2/PMHS system.
- Wang, Hu,Li, Li,Bai, Xing-Feng,Shang, Jun-Yan,Yang, Ke-Fang,Xu, Li-Wen
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supporting information
p. 341 - 347
(2013/05/08)
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- Easy eco-friendly phenonium ion production from phenethyl alcohols in dimethyl carbonate
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An efficient and simple one-pot procedure for selective etherification of 2-aryl-ethylalcohols has been achieved through Amberlyst 15-catalyzed reaction in dimethyl carbonate (DMC). Moreover, the polymer catalyst could be recovered and reused with no effect on its activity. The reaction mechanism involves the formation of phenonium ion which has been demonstrated by a C-C bond forming reaction. Theoretical studies are in agreement with and thus explain experimental results.
- Barontini,Proietti Silvestri,Nardi,Bovicelli,Pari,Gallucci,Spezia,Righi
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supporting information
p. 5004 - 5006
(2013/08/28)
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- Cross-coupling of alkyl halides with aryl or alkyl Grignards catalyzed by dinuclear Ni(ii) complexes containing functionalized tripodal amine-pyrazolyl ligands
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Structurally distinctive dinuclear Ni(ii) complexes with furan or thiophene tethered amine-pyrazolyl tripodal hybrid ligands have been synthesized and crystallographically characterized. All complexes are catalytically active towards cross-coupling of aryl/alkyl Grignard reagents with β-H containing alkyl halides at room temperature in the presence of N,N,N',N'- tetramethylethylenediamine (TMEDA). The catalytic efficacy of the complexes is dependent on the tether substituent at the central amine. Two species, Ni(ii) TMEDA and Mg(ii) TMEDA complexes, have been isolated from the catalytic reaction mixtures under different conditions. Some ligand-stabilized Ni(ii) and Mg(ii) bimetallic species have also been identified in the ESI-MS spectra.
- Xue, Fei,Zhao, Jin,Hor, T. S. Andy
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p. 5150 - 5158
(2013/04/10)
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- Iron-catalyzed hydrosilylation of esters
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The first hydrosilylation of esters catalyzed by a well defined iron complex has been developed. Esters are converted to the corresponding alcohols at 100 °C, under solvent-free conditions and visible light activation. Copyright
- Bezier, David,Venkanna, Gopaladasu T.,Castro, Luis C. Misal,Zheng, Jianxia,Roisnel, Thierry,Sortais, Jean-Baptiste,Darcel, Christophe
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scheme or table
p. 1879 - 1884
(2012/09/22)
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- Spin trapping studies on radical cations of styrene
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The radical cations of styrene (π-type), generated by photosensitized electron-transfer of 1,4-dicyanobenzene (DCB), using 2-methyl-2-nitrosopropane (MNP) as spin trapping agents and nucleophiles as the co-reactant were investigated. The spin-trapped nitr
- Ho, Tong-Ing,Lin, Chiou-Rong,Pan, Kai,Hsu, Chi-Wei
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p. 983 - 986
(2007/10/03)
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- Reduction of carboxylic esters to ethers with triethyl silane in the combined use of titanium tetrachloride and trimethylsilyl trifluoromethanesulfonate
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Aliphatic acyclic and cyclic ethers are prepared on treatment of their corresponding carboxylic esters and lactones with triethylsilane in the presence of titanium tetrachloride and trimethylsilyl trifluoromethanesulfonate.
- Yato,Homma,Ishida
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p. 5353 - 5359
(2007/10/03)
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- Batch microwave reactor
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An apparatus for performing batchwise chemical reactions using microwave energy (10-11-12) includes a vessel (15) within a microwave cavity (13). The vessel has a sealed cover (16), located outside cavity (13), which mounts a cold-finger type heat exchanger (24) for immersion in the vessel's contents (23). Cover (16) also mounts a pressure measuring device (17) and a temperature sensing device (20) for monitoring the vessel's contents during a chemical reaction. A pressure operable safety valve (18) and a sampling facility (19) are also mounted on the cover (16). The vessel also contains a magnetically operated stirrer (22). The reactor apparatus is constructed to withstand high pressures and temperatures that may be developed within the vessel (15). Various uses of the cold-finger (24) to facilitate the conduct or completion of a chemical reaction are described.
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- Calcium metal in liquid ammonia for selective reduction of organic compounds
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Selective reduction of functional groups by use of dissolving calcium metal was performed, and the results are in comparison with those by lithium and sodium metals. Reduction with 2.0-2.2 equiv of calcium led chromone (1) to 4-chromanone (2, 75% yield), coumarin (4) to dihydrocoumarin (5, 76% yield) and 3-(2-hydroxyphenyl)-1-propanol (6, 6% yield), α-tetralone (7) to 1,2,3,4-tetrahydro-1-naphthol (8, 81% yield), and β-methoxystyrene (12) to methyl phenethyl ether (13, 85% yield). Performance of reductions on the same substrates by use of 4.0 equiv of lithium or sodium metal gave over-reduced products. Reduction of indole-3-carboxaldehyde (15) to 3-indolemethanol (16), 1-acetylnaphthalene (17) to 1-acetyl-3,4-dihydronaphthalene (18), and trans-4-phenyl-3-buten-2-one (19) to 4-phenyl-2-butanone (20) were accomplished by use of calcium, lithium, and sodium metals, among which calcium gave the highest yields (80-90%). Being a milder reducing agent than lithium and sodium, calcium metal in liquid ammonia offered a better selectivity.
- Hwu, Jih Ru,Wein,Leu, Yi-Jing
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p. 1493 - 1498
(2007/10/03)
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- Anodic oxidation of 3-phenylpropionic acid
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The electrochemical oxidation of 3-phenylpropionic acid has been performed on platinum, graphite and PtO2/Ti anodes. Two types of products have been obtained, either formed by one-electron oxidation, or by two-electron oxidation. The influence of the anode material, current density and solvent nature on the products distribution has been studied. The electrochemical oxidations of 3-(p-t-butylphenyl)propionic, 3,3-d-3-phenylpropionic and 2,2-d-3-phenylpropionic acids have been studied in order to get information concerning the carbonium-type intermediate in the two-electron oxidation. Unlike the chemical generation, the 2-phenylethyl carbocation formed by two-electron oxidation stabilises, leading mainly to rearranged products. The obtained results are in agreement with the assumption that either phenyl or σC-H bond assists the carbocation formation.
- Ro?ca, Sorin,Ungureanu, Mihaela,Stan, Raluca
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- A New Microwave Reactor for Batchwise Organic Synthesis
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A laboratory-scale microwave batch reactor (MBR) has been developed for organic synthesis or kinetic studies on the 20-100 mL scale, with upper operating limits of 260 deg C and 10 MPa (100 atm).The MBR complements a continuous microwave reactor which was the subject of a previous report from the author's laboratory.Microwave-assisted organic reactions were conducted safely and conveniently in the MBR, for lengthy periods when required, and in volatile organic solvents.The use of water as a solvent for organic reactions was also explored.Examples include oxidation, elimination, esterifications, hydrolysis of a tertiary amide, etherification, isomerization, Hofmann elimination, α-iodination of a carboxylic acid, Claisen rearrangement, aminoreductone formation, and Willgerodt reactions.Advantages of the new MBR include the capability for rapid heating and quenching of reaction mixtures, minimal temperature gradients within the sample, and elimination of wall effects.Safety aspects have been discussed.
- Raner, Kevin D.,Strauss, Christopher R.,Trainor, Robert W.,Thorn, John S.
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p. 2456 - 2460
(2007/10/02)
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- Preparation of zirconium (benzyldiethylammoniomethylphosphonate chloride) and PTC reactions
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Zirconium (benzyldiethylammoniomethylphosphonate chloride)phosphate Zr(HPO4)2-x (O2PCH2N+Et2CH2ph·Cl-)x·H2O, (0.25 x 0.75, ZBEPC-ZP) were prepared for the first time and characterized by IR and elemental analyses. ZBEPC-ZP catalyzed some typical PTC reactions in L/S/L phases were carried out to give good results. ZBEPC-ZP can be easily separated from the reaction mixture and recovered about 70-100%, and can be reused and did not show any change in activity after 10 cycles.
- Fu,Wen
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p. 2435 - 2442
(2007/10/02)
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- Development and Application of a Continuous Microwave Reactor for Organic Synthesis
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A laboratory-scale continuous microwave reactor (CMR) has been developed and used to conduct organic syntheses routinely, rapidly, and safely in a range of solvents, under pressures up to 1400 kPa and at temperatures up to 200 deg C.Advantages and applications of the CMR are discussed, along with the rationale for the design.Reactions carried out with the CMR included nucleophilic substitution, addition, esterification, transesterification, acetalization, amidation, base- and acid-catalyzed hydrolysis, isomerization, decarboxylation, and elimination.Name reactions included the Michael addition, Hofmann degradation, Williamson ether synthesis, and the Mannich, Finkelstein, Baylis-Hillman, and Knoevenagel reactions.
- Cablewski, Teresa,Faux, Alan F.,Strauss, Christopher R.
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p. 3408 - 3412
(2007/10/02)
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- ONE ELECTRON OXIDATION OF BENZYL AND 2-PHENYLETHYL PHENYL ETHERS. THE FATE OF THE INTERMEDIATE RADICAL CATIONS
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The one electron oxidations of benzyl phenyl ether (1), 2-phenylethyl phenyl ether (2) and 2-(4-methoxyphenyl)ethyl phenyl ether (3) promoted (a) by cerium(IV) ammonium nitrate (CAN) in AcOH, (b) electrochemically in AcOH-MeCN/AcOK and (c) photochemically in MeCN, in the presence of 9,10-dicyanoanthracene (DCA), have been investigated.With 1 benzaldehyde forms, under all the reaction conditions, accompanied by products of acetoxylation at the phenoxy ring (conditions a and b) or by phenyl benzoate (condition c).The CAN-promoted and the electochemical oxidation of 2 exclusively lead to substitution at the phenoxy ring, whereas only side-chain attack at the benzylic carbon occurs in all of the reactions of 3, with formation of 4-methoxybenzaldehyde and products of side-chain oxidation.Phenyl 4-methoxybenzoate is also formed (conditions b and c).However, when the electrochemical oxidation is carried out in the absence of AcOK, only a product of intermolecular ring closure forms.These results allow one to draw some interesting conclusion on the competition between the various reaction pathways available to the cation radicals which are the first formed reaction intermediates in these one electron processes.
- Baciocchi, Enrico,Piermattei, Alessandro,Rol, Cesare,Ruzziconi, Renzo,Sebastiani, Giovanni Vittorio
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p. 7049 - 7062
(2007/10/02)
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- Photosensitized (electron transfer) carbon-carbon bond cleavage of radical cations: the 2-phenylethyl ether and acetal systems
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The scope of the photosensitized (electron transfer) carbon-carbon bond cleavage involving radical cations has been defined for 2-phenylethyl ethers and acetals.The thresholds for reactivity of the monophenylethyl and gem-diphenylethyl derivatives are compared.While the radical cation of methyl 2,2-diphenylethyl ether (7) cleaves to give ultimately diphenylmethane (2) and dimethoxymethane (8), the radical cation of methyl 2-phenylethyl ether (9) was stable under these conditions.In contrast to the lack of reactivity of the radical cation of 9, the radical cations of methyl 2-phenyl-2-propyl ether (11), methyl 2-phenylcyclopentyl ether (13), and 2-phenylmethyl-1,3-dioxolane (16) cleave.Cleavage in the monophenylethyl series is limited to formation of a carbocation at least as stable as the secondary α-oxyalkyl or di-α-oxyalkyl.The basis for predicting this type of reactivity of radical cations is defined.The rate of carbon-carbon bond cleavage is increased the oxidation potential of the molecule, by decreasing the carbon-carbon bond strength, and (or) by decreasing the oxidation potential of that fragment that will become the carbocation.The results obtained from the reactions of 2-diphenylmethyl-1,3-dioxolane (14) and 2-phenylmethyl-1,3-dioxolane (16) cast doubt on the published oxidation potential for the 1,3-dioxolan-2-yl radical.Key words: photochemistry, radical cation, electron transfer, bond cleavage, radical.
- Arnold, Donald R.,Lamont, Laurie J.
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p. 2119 - 2127
(2007/10/02)
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- Gas-Phase Acid-Induced Nucleophilic Displacement Reactions. 8. Structural Analysis of Intermediate Ions Formed by the Decomposition of β-Arylethyl Onium Ions
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The existence of the stable unsubstituted ethylenebenzenium ion 3 as a stable gaseous species is inferred as occuring in the reaction pathway induced by the attack of radiolytically formed gaseous acids GA+ (GA+ = D3+, CnH5+ (n = 1,2), and CH3FCH3+) on β-phenyl-Y-ethanes (Y = F, Cl, and OH).Neutral product analysis allows use to define the detailed reaction mechanism and to extend previous conclusions concerning adjacent phenyl group participation in the nucleophilic displacement process, which take place in competition with 1,2-H migration.Occurence of alternative cyclic structures, e.g. 7, in the participation step is ruled out on the grounds of results of specifically designed radiolytic expriments.The mechanistic picture that caracterizes neighboring phenyl-group participation in cationic nucleophilic substitutions occuring in the gas phase presents interesting analogies with related processes occuring under solvolytic conditions and in superacidic media.The results from the present gas-phase radiolytic approach are discussed and contrasted with pertinent mass spectrometric data and theoretical predictions.
- Fornarini, Simonetta,Sparapani, Cinzia,Speranza, Maurizio
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- The Mechanism of Thermal Eliminations. Part 25. Arrhenius Data for Pyrolysis of Isochroman-3-one, Benzyl Methyl Ether, 2-Hydroxyethylbenzene, Phenyl Acetate, and 3,4-Dihydro-2H-pyran
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The thermal decomposition of isochroman-3-one to benzocyclobutene and carbon dioxide, of benzyl methyl ether and 2-hydroxyethylbenzene to toluene and formaldehyde, and of phenyl acetate to phenol and ketene are each first-order unimolecular reactions.The Arrhenius parameters -1, log (A/s-1> are 221.1, 14.305; 231.7, 12.92; 200.5, 11.21; and 221.8, 11.78, respectively.The frequency factors indicate that each reaction involves a cyclic semi-concerted mechanism; for phenyl acetate this is a four-centre process analogous to that involved in the formation of ketene from pyrolysis of either acetic acid, acetyl bromide, or acetamide.The higher log (A/s-1) value for isochroman-3-one is typical of elimination from cyclic compounds, because their ground states are already constrained into the geometry required in the transition state.Chroman-1-one (dihydrocumarin) is very much more stable than isochroman-3-one (and on decomposition gives mainly coumarin and benzofuran, evidently due to the favourable gain in aromacity).Decomposition of 3,4-dihydro-2H-pyran into ethene and propenal takes place according to the rate equation log k=13.556-209.01/19.142 K, the rate coefficients being lower than the literature values which may therefore have been affected by surface catalysis.A 2-methyl group in the pyran produces a ca. 4.5-fold rate acceleration, very similar to that produced in the analogous vinyl ethers.The relationship between the elimination rates for a range of cyclic compounds and their open-chain counterparts is examined and it is found that their reactivities are closely similar.Hydrogen is shown to be transferred as an incipient anion in allyl ether pyrolysis, whereas in most eliminations it is transferred as an incipient cation.
- Taylor, Roger
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p. 183 - 190
(2007/10/02)
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- PHOTOLYSIS OF 2-PHENYLETHYL AND 4-PHENYL-1-BUTYL HALIDES IN ALCOHOLIC SOLVENTS
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Photolysis of 2-phenylethyl bromide in the lower alcohols gave the corresponding carbinols and ethers as the main products.With 2-phenylethyl iodide, the products were almost exclusively of the latter type, while 4-phenyl-1-butyl halides gave n-butylbenzene, 4-phenyl-1-butene and tetralin.It is shown that each of these products may be assigned to an ionic or radical pathway and that both the nature of the sovent and the structure of the substrate affect the course of photolysis.There is a substrate dependent preference for specific reactions along pathways of both the radical and ionic types.The variations in product composition and distribution are rationalized in terms of the relative efficiencies furnished in these pathways for the relaxation of high energy intermediates produced in the initial stages of photolysis.Intervention by the phenyl group is more pronunced in the case of 2-phenylethyl halides than in the case of the higher homologues and more effective in the ionic pathway.
- Bhalerao, V. K.,Nanjundiah, B. S.,Sonawane, H. R.,Nair, P. M.
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p. 1487 - 1496
(2007/10/02)
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- Electrosynthesis of Organic Compounds, VII. Electrochemical Oxidation of Selected Arylalkyl Halides
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Anodic oxidation of selected arylalkyl halides was carried out in methanol containing 0.05 mol.l-1 Ba(ClO4)2, as electrolyte on a platinum anode at + 1.7 V vs SCE.The compounds electrochemically oxidized were benzyl bromide (1), 2-phenylethyl bromide (2), 3-phenylpropyl bromide (3), 4-phenylbutyl chloride (4), 1-methyl-3-phenylpropyl chloride (5) and 1,1-dimethyl-3-phenylpropyl chloride (6).The principal products isolated were the corresponding alkylbenzenes, alkenylbenzenes, dimers, ethers and cyclic products.Mechanisms were suggested.Also, kinetic studies were carried out on carbon-halogen bond cleavage of the compounds investigated (1-6).Current-potential curves were drawn, and discharge oxidation potentials were determined from these.
- Ismail, M. T.,Abdel-Wahab, A. A.,El-Khawaga, A. M.,Mohamed, O. S.,Khalaf, A. A.
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- Oxidation of Alkyl Phenyl Selenides, Tellurides, and Telluroxides with meta-Chloroperbenzoic Acid for a Facile and Novel Transformation of C-Se and C-Te Bonds to C-O Bonds
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In sharp contrast to the well-known selenoxide elimination leading to olefins, the treatment of alkyl phenyl selenides (PhSeR) with an excess of meta-chloroperbenzoic acid (MCPBA; 2-5 equiv. to a selenide) in alcohol at room temperature affords the corresponding dialkyl ethers by the substitution of a phenylselenium (PhSe) moiety with an alkoxy group.A similar reaction proceeds by using alkyl phenyl tellurides (PhTeR) and telluroxides , a facile substitution of PhTe or PhTe(O) moiety by an alkoxy group being observed.Methanol is the most appropriate solvent for these oxidations and alkyl methyl ethers are formed in excellent yields.The reaction is accompanied by phenyl migration when applied to some selenides, tellurides, and telluroxides having a phenyl group at a vicinal position to the PhSe, PhTe, or PhTe(O) moiety.Application to the methoxyselenation and methoxytelluration products of cyclohexene and cycloheptene results in a ring-contraction to afford the dimethyl acetals of cyclopentane- and cyclohexane-carbaldehyde, respectively.In case of an allylic phenyl selenide, a sigmatropic rearrangement giving a rearranged allylic alcohol occurs in much preference to the substitution by the methoxy group.Other oxidizing agents than MCPBA such as NaIO4, H2O2, t-BuOOH, and ozone are generally ineffective under similar conditions.It is proposed that the reaction mainly takes place as follows.Alkyl phenyl selenone, alkyl phenyl tellurone, or the MCPBA addition product to them is formed as a reactive intermediate in which an alkyl C-Se or alkyl C-Te bond fission occurs heterolytically by a nucleophilic attack of alcohol, sometimes accompanied by a 1,2-shift of the β-substituent, i.e., phenyl migration and ring-contraction.
- Uemura, Sakae,Fukuzawa, Shin-ichi
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p. 471 - 480
(2007/10/02)
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- The influence of a base on the methylation of aminoalchols
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A selective methylation towards N and O atoms on aminoalcohols was observed using metal hydride reagents as the base, and the predominant factors for the selectivity were investigated in detail.
- Kashima, Choji,Harada, Kazuo,Omote, Yoshimori
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p. 288 - 290
(2007/10/02)
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- Alcoxymethyltributyletains precurseurs d'alcoxymethyllithiums: application a la synthese de monoethers d'α-glycols et a l'homologation de cetones en aldehydes
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Ethoxymethyltributyltin (obtained from diethoxymethyltributyltin, acetyl chloride and tributyltin hydride) and methoxymethyltributyltin (obtained from chloromethyl-methyl ether and tributylstannylmagnesium chloride) have been transmetallated with butyllithium to give the corresponding alkoxymethyl lithium reagents.This reaction, although usually performed in ether, is possible in a variety of other solvents thus simplifying some of the problems encountered during isolation of the products.The alkoxymethyllithiums obtained react with aldehydes and ketones to give cleanly the corresponding monoprotected α-glycols.Stereochemical trends were observed for hydratropaldehyde and 4-tertiarybutylcyclohexanone, while regiochemical trends were evaluated in the case of cyclohexen-2-one.Syntheis of aldehydes has been achieved in good yields from tertiary monoprotected α-glycols using conventional methods.
- Duchene, Alain,Mouko-Mpegna, David,Quintard, Jean-Paul
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p. 787 - 793
(2007/10/02)
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- Anodic Oxidation of Organoboranes
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Organoboranes are converted into more easily oxidizable borates by reaction with nucleophiles and the alkyl groups are dimerized by anodic oxidation.The oxidation potentials (Ep) of the borates depend strongly on the nature of the complexing nucleophile, for instance Ep = +0.37 V (vs.SCE) with OH- or +1.65 V with tetrahydrofuran.The dimer yields are optimized with trioctylborane (5) by variation of the electrode material and the elctrolyte.At the platinum anode in sodium hydroxide-methanol/tetrahydrofuran yields of 80percent are obtained for acyclic alkyl groups, and lo wer ones for cycloalkyl groups.They exceed those obtained by the Kolbe electrolysis or the oxidation with neutral hydrogen peroxide and they are comparable to those of the AgNO3 oxidation. - The selective preparation of unsymmetrical products from borates with different alkyl groups is not possible, the dimerization proceeds likely via free radicals that couple statistically.Good yields of unsymmetrical coupling products are achieved, when one olefin is used in excess.With choro-, ethoxy-, acetoxy-, and aryl-substituted alkyl groups the dimers are obtained in 21 - 66percent yield, with bromide the yield are lower and with nitriles the dimerization fails.
- Schlegel, Guenter,Schaefer, Hans J.
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p. 1400 - 1423
(2007/10/02)
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- NOVEL OXIDATION OF ALKYL PHENYL TELLURIDES AND TELLUROXIDES WITH meta-CHLOROPERBENZOIC ACID: REPLACEMENT OF TELLURIUM MOIETY BY METHOXY GROUP ACCOMPAINED BY RING CONTRACTION AND PHENYL MIGRATION
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Oxidation of alkyl phenyl tellurides and telluroxides with meta-chloroperbenzoic acid in methanol at room temperature afforded the corresponding alkyl methyl ethers in high yields.The reaction was accompained by phenyl migration and ring-contraction respectively when applied to the compounds having phenyl group next to the tellurium moiety and to the methoxytelluration products of cyclic olefins.
- Uemura, Sakae,Fukuzawa, Shin-ichi
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p. 4347 - 4350
(2007/10/02)
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- Esters of α-Arylalkanoic Acids from 'Masked' α-Halogenoalkyl Aryl Ketones and Silver Salts: Synthetic, Kinetic, and Mechanistic Aspects
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A method for the synthesis of alkyl esters of α-arylalkanoic acids is given based on silver-ion-assisted (AgBF4, AgOSO2CF3, AgSbF6, AgNO3) solvolysis of alkyl acetals of primary and secondary α-halogenoalkyl aryl ketones (Hal = I, Br, Cl) in an alcoholic medium (methanol, ethanol).The reaction is quite selective and alkyl esters are the only reaction products; ethers, which are possible substitution products, are not found.The importance of masking the carbonyl as the acetal is emphasised.The reaction is found to be first-order in AgBF4 and in the primary α-halogeno acetal.A three-point Hammett correlation (ρ = -3.29) between ?+ and the rate constants suggests a large cationic contribution as well as strong aryl participation in the transition state.The role payed by the oxygen of the acetal group in the specificity of the reaction is discussed in comparison with the reactivity of analogous compounds with saturated skeletons and of α-halogenoalkyl aryl ketones.
- Giordano, Claudio,Castaldi, Graziano,Casagrande, Francesco,Belli, Aldo
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p. 2575 - 2582
(2007/10/02)
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- FLUORIDE SALTS ON ALUMINA AS REAGENTS FOR ALKYLATION OF PHENOLS AND ALCOHOLS.
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THE EFFECTIVENESS OF ALKALI METAL FLUORIDES IMPREGNATED ON ALUMINA AS A REAGENT FOR PROMOTING ALKYLATION WAS OPTIMIZED WITH RESPECT TO THE METAL CATION, THE AMOUNT OF IMPREGNATION, AND THE REACTION SOLVENT. POTASSIUM OR CAESIUM FLUORIDE ONALUMINA IN ACETONITRILE OR 1,2-DIMETHOXYETHANE WAS CONCLUDED TO BE THE BEST REACTION SYSTEM FOR GENERAL USE. O-ALKYLATION OF SUBSTITUTED PHENOLS, PRIMARY AND SECONDARY ALCOHOLS, AND A GLYCOL WAS CARRIED OUT MOSTLY IN GOOD YIELDS UNDER MILDCONDITIONS WITH SIMPLE EXPERIMENTAL PROCEDURES.
- ANDO,YAMAWAKI,KAWATE,SUMI,HANAFUSA
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p. 2504 - 2507
(2007/10/02)
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- Mercury-assisted solvolyses of alkyl halides. Simple procedures for the preparation of nitrate esters, acetate esters, alcohols and ethers
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The reactions of a wide variety of alkyl halides with mercury(I) and/or (II) nitrate in 1,2-dimethoxyethane, mercury(II) acetate in acetic acid, aqueous mercury(II) perchlorate, and mercury(II) perchlorate in alcohol solvents have been investigated; as a result, simple high yield procedures for the conversion of alkyl halides into the corresponding nitrate esters, acetate esters, alcohols and ethers have been developed.
- McKillop,Ford
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p. 2467 - 2475
(2007/10/05)
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