- Potential for release of pulmonary toxic ketene from vaping pyrolysis of Vitamin E acetate
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A combined analytical, theoretical, and experimental study has shown that the vaping of vitamin E acetate has the potential to produce exceptionally toxic ketene gas, which may be a contributing factor to the upsurge in pulmonary injuries associated with using e-cigarette/ vaping products. Additionally, the pyrolysis of vitamin E acetate also produces carcinogen alkenes and benzene for which the negative long-term medical effects are well recognized. As temperatures reached in vaping devices can be equivalent to a laboratory pyrolysis apparatus, the potential for unexpected chemistries to take place on individual components within a vape mixture is high. Educational programs to inform of the danger are now required, as public perception has grown that vaping is not harmful.
- O'Shea, Donal F.,Wu, Dan
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Read Online
- Photoelectron Transfer between a Magnesium-Free-Base Porphyrin Heterodimer and Duroquinone. Selective Excitation and Time-Resolved EPR Studies
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The photoexcited triplet state of a cofacial heterodimer, , comprised of Mg and H2 porphyrins, and photoinduced electron transfer (ET) between the heterodimer and duroquinone in 1:1 mixture of CH2Cl2/ethanol were studied by selective laser excitation combined with time-resolved CW or with pulsed EPR spectroscopies.ET originates from the photoexcited triplet or triplet radical pair states.Upon photoexcitation of the Mg subunit (580 nm), a noticeable delay time of ca.20 ns in ET is observed, whereas with photoexcitation of the H2 part (620 nm), no delay time in ET is noticed.The dependence of ET upon excitation wavelength is interpreted in terms of the formation and participation of a charge-transfer state that is operative at 205 K.The delay time is attributed to an intradimer ET that produces the triplet radical pair state 3.+-H2.->.Photoexcitation at 620 nm results in ET via the lower-lying triplet of H2 without involvement of the chargetransfer state.
- Levanon, Haim,Regev, Ayelet,Galili, Tamar,Hugerat, Muhamad,Chang, Chi K.,Fajer, Jack
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Read Online
- Pentamethylphenyl (Ph*) and Related Derivatives as Useful Acyl Protecting Groups for Organic Synthesis: A Preliminary Study
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A study of acyl protecting groups derived from the Ph? motif is reported. While initial studies indicated that a variety of functional groups were not compatible with the Br 2-mediated cleavage conditions required to release the Ph? group, strategies involving the use of different reagents or a modification of Ph? itself (Ph*OH) were investigated to solve this problem.
- Cheong, Choon Boon,Frost, James R.,Donohoe, Timothy J.
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p. 1828 - 1832
(2020/10/06)
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- Photocatalytic Hydrogen Evolution from Plastoquinol Analogues as a Potential Functional Model of Photosystem I
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The recent development of a functional model of photosystem II (PSII) has paved a new way to connect the PSII model with a functional model of photosystem I (PSI). However, PSI functional models have yet to be reported. We report herein the first potential functional model of PSI, in which plastoquinol (PQH2) analogues were oxidized to plastoquinone (PQ) analogues, accompanied by hydrogen (H2) evolution. Photoirradiation of a deaerated acetonitrile (MeCN) solution containing hydroquinone derivatives (X-QH2) as a hydrogen source, 9-mesityl-10-methylacridinium ion (Acr+-Mes) as a photoredox catalyst, and a cobalt(III) complex, CoIII(dmgH)2pyCl (dmgH = dimethylglyoximate monoanion; py = pyridine) as a redox catalyst resulted in the evolution of H2 and formation of the corresponding p-benzoquinone derivatives (X-Q) quantitatively. The maximum quantum yield for photocatalytic H2 evolution from tetrachlorohydroquinone (Cl4QH2) with Acr+-Mes and CoIII(dmgH)2pyCl and H2O in deaerated MeCN was determined to be 10%. Photocatalytic H2 evolution is started by electron transfer (ET) from Cl4QH2 to the triplet ET state of Acr+-Mes to produce Cl4QH2?+ and Acr?-Mes with a rate constant of 7.2 × 107 M-1 s-1, followed by ET from Acr?-Mes to CoIII(dmgH)2pyCl to produce [CoII(dmgH)2pyCl]-, accompanied by the regeneration of Acr+-Mes. On the other hand, Cl4QH2?+ is deprotonated to produce Cl4QH?, which transfers either a hydrogen-atom transfer or a proton-coupled electron transfer to [CoII(dmgH)2pyCl]- to produce a cobalt(III) hydride complex, [CoIII(H)(dmgH)2pyCl]-, which reacts with H+ to evolve H2, accompanied by the regeneration of CoIII(dmgH)2pyCl. The formation of [CoII(dmgH)2pyCl]- was detected by electron paramagnetic resonance measurements.
- Fukuzumi, Shunichi,Hong, Young Hyun,Lee, Yong-Min,Nam, Wonwoo
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p. 14838 - 14846
(2020/11/03)
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- Bismuth-catalyzed methylation and alkylation of quinone derivatives with tert-butyl peroxybenzoate as an oxidant
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A bismuth-catalyzed methylation of quinones in the presence of tert-butyl peroxybenzoate (TBPB) was developed via a radical reaction mechanism. Particularly, TBPB was used not only as an efficient oxidant, but also as a green methyl source in such transformation. Moreover, this method could also be efficiently extended to the alkylation of quinones. This reaction tolerated a series of functional groups and prepared a series of derivatives of vitamin K3 and benzoquinone. Notably, antimalarial parvaquone was synthesized by the reaction.
- Yang, Jian,Dong, Yu,He, Shuai,Shi, Zhi-Chuan,Wang, Yu,Wang, Ji-Yu
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- Synthesis and characterization of a novel ruthenium(ii) trisbipyridine complex magnetic nanocomposite for the selective oxidation of phenols
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Anchoring ruthenium(ii) trisbipyridine complex [Ru(Bpy)3]2+ into a magnetic dendritic fibrous silica nanostructure produces an unprecedented strong nanocatalyst, FeNi3/DFNS/[Ru(Bpy)3]2+. Impressive oxidation of phenols to 1,4-benzoquinones catalyzed by FeNi3/DFNS/[Ru(Bpy)3]2+ is obtained in acetonitrile and water solution with molecular dioxygen as oxidant. Exclusively, apparently inert phenols such as phenol itself and mono-alkyl-substituted phenols are impressively oxidized to produce 1,4-benzoquinones through activation of the C-H bond in the position para to the carbon-oxygen bond under mild conditions. In addition, the production of industrially significant quinones that are known intermediates for vitamin combinations is investigated and studied FeNi3/DFNS/[Ru(Bpy)3]2+ magnetic nanoparticles were produced, and their properties were investigated by AFM, FTIR, XRD, TGA, SEM, TEM, and VSM.
- Fei, Zhengxin,Chen, Feng,Zhong, Mingqiang,Qiu, Jianping,Li, Weidong,Sadeghzadeh, Seyed Mohsen
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p. 28078 - 28088
(2019/09/30)
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- Selective activation of C–H bond into C[dbnd]O bond of phenols in para-position via aerobic oxidation
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An efficient method for the oxidation of phenols to 1,4-benzoquinones catalyzed by cuprous(I) chloride was achieved in a solution of acetonitrile and water using molecular dioxygen as an oxidant. Particularly, the inert phenols, such as phenol and mono-alkyl substituted phenols, were effectively oxidized to 1,4-benzoquinones via the selective activation of C–H bond in para-position into C[dbnd]O bond under mild conditions. The catalyst shows high activity for unsubstituted or alkyl substituted phenols, but no effect on substituted phenols with electron-withdrawing groups. This study offers an aerobic method for the selective oxidation of aromatic phenols to 1,4-benzoquinones.
- Yang, Shilei,Xu, Guoqiang,Shi, Song,Xin, Hongchuan,Gao, Jin,An, Zengjian
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p. 105 - 108
(2019/02/25)
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- Selective iron-catalyzed oxidation of phenols and arenes with hydrogen peroxide: Synthesis of vitamin e intermediates and vitamin k3
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(Figure Presented). Pumping iron! Convenient iron-based catalyst systems for the selective oxidation of arenes and phenols with hydrogen peroxide to give 1, 4-quinones have been developed. This selective oxidation reaction takes place under mild conditions (room temperature, alcoholic solvents) with H 2O2 as the terminal oxidant.
- Moeller, Konstanze,Wienhoefer, Gerrit,Schroeder, Kristin,Join, Benoit,Junge, Kathrin,Beller, Matthias
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experimental part
p. 10300 - 10303
(2010/10/21)
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- Polymer incarcerated gold catalyzed aerobic oxidation of hydroquinones and their derivatives
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Polymer-incarcerated gold (PI Au) cluster catalysts mediated aerobic oxidation of hydroquinones and catechols to quinones very efficiently under mild conditions. The characteristic role of water in the reaction system was also observed. Copyright
- Miyamura, Hiroyuki,Shiramizu, Mika,Matsubara, Ryosuke,Kobayashi, Shu
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p. 360 - 361
(2008/09/20)
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- Aerobic oxidation of hydroquinone derivatives catalyzed by polymer-incarcerated platinum catalyst
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(Chemical Equation Presented) It's a lock-in! A remarkably wide substrate scope of hydroquinones are oxidized to quinones in high yields in a platinum-catalyzed process with as low as 0.05 mol% catalyst. The aerobic oxidation is catalyzed by platinum nanoclusters trapped in a styrene-based polymer network (see scheme, PI Pt=polymer-incarcerated nanoclusters). The catalyst could be reused at least 13 times without any loss of catalytic activity.
- Miyamura, Hiroyuki,Shiramizu, Mika,Matsubara, Ryosuke,Kobayashi, Shu
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supporting information; experimental part
p. 8093 - 8095
(2009/04/13)
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- Intramolecular hydroarylation of alkynes catalyzed by platinum or gold: Mechanism and endo selectivity
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The cyclization of differently substituted aryl alkynes with Pt II or AuI catalysts proceeds by endo-dig pathways. When AgI was used to generate reactive cationic AuI catalysts, 2H-chromenes dimerize to form cyclobutane derivatives by a Ag I-catalyzed process. A DFT study on the cycliza-tion mechanism shows a kinetic and thermodynamic preference for 6-endodig versus 5-exo-dig cyclizations in PtII-catalyzed processes. Calculations indicate that although Friedel-Crafts and the cyclopropanation processes via metal cyclopropyl carbenes show very similar activation energies, platinum cyclopropyl carbenes are the stationary points with the lowest energy.
- Nevado, Cristina,Echavarren, Antonio M.
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p. 3155 - 3164
(2007/10/03)
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- Photoreduction of p-Benzoquinones: Effects of Alcohols and Amines on the Intermediates and Reactivities in Solution
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The photochemistry of 1,4-benzoquinone (BQ) and alkyl-, Cl- and related derivatives, e.g. methyl-, 2,6-dimethyl-, chloro-, 2,5-dichloro-1,4-benzoquinone, duroquinone and chloranil, was studied in nonaqueous solvents by UV-vis spectroscopy using nanosecond laser pulses at 308 nm. The reactivity of the triplet state (3Q*) of the quinones with 2-propanol in the absence of water is largest for BQ and depends mainly on the quinone structure, whereas the rate constant of electron transfer from amines, such as triethylamine (TEA) or 1,4-diazabicyclo[2.2.2]octane, is close to the diffusion-controlled limit for BQ and most derivatives. Photoinduced charge separation after electron transfer from amines to 3Q* and the subsequent charge recombination or neutralization are supported by time-resolved conductivity measurements. The half-life of the decay kinetics of the semiquinone radical (.QH/Q.-) depends significantly on the donor and the medium. The photoconversion into the hydroquinones was measured under various conditions, the quantum yield, λirr = 254 nm, increases with increasing 2-propanol and TEA concentrations. The effects of quenching of 3Q*, the .QH/Q.- radicals and the photoconversion are outlined. The mechanisms of photoreduction of quinones in acetonitrile by 2-propanol are compared with those by TEA in benzene and acetonitrile, and the specific properties of substitution are discussed.
- Goerner, Helmut
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p. 440 - 448
(2007/10/03)
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- Facile and efficient sulfenylation method using quinone mono-O,S-acetals under mild conditions
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A novel sulfenylation method induced by aromatization of quinone mono-O,S-acetals is described. These sulfenylation reagents readily react with silyl enolethers or electron rich aromatic compounds to give sulfenylation products under mild conditions. In particular, O,S-acetal 2j, which possesses a pentafluorophenylthio function, is the most effective reagent from the standpoint of the adaptability for various substrates.
- Matsugi,Murata,Gotanda,Nambu,Anilkumar,Matsumoto,Kita
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p. 2434 - 2441
(2007/10/03)
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- Unusual oxidative cleavage of the aryl-ethynyl bonds in (arylethynyl)polymethylbenzenes with iodine in dimethyl sulfoxide
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While heating 1,2,4,5-tetramethyl-3,6-bis(phenylethynyl)benzene, 1,3,5-trimethyl-2,4-bis(phenylethynyl)benzene, and 1,2,4,5-tetramethyl-3-(phenylethynyl)benzene with iodine in DMSO in the absence of oxygen, the triple bonds are oxidized to give the corresponding 1,2-diketones. In the presence of oxygen, the previously unknown competitive oxidative process causes the cleavage of the aryl-ethynyl bonds so that duroquinone and the corresponding 4-hydroxybenzils are formed. This cleavage is produced by oxygen only in the presence of iodine and DMSO. It was shown that the key stage of the process is the formation of intermediate charge-transfer complexes between polymethylbenzene rings and iodine.
- Yusubov,Zholobova,Filimonova,Vasil'eva,Filimonov,Chi, Ki-Whan
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p. 1051 - 1055
(2007/10/03)
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- The dichotomy between nitration of substituted 1,4-dimethoxybenzenes and formation of corresponding 1,4-benzoquinones by using nitric and sulfuric acid
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Various alkyl-substituted p-dimethoxybenzenes (ArH) react readily With nitric acid and sulfuric to form nitroproducts (ARNO2). When the nitric acid is used in excess, the nitro-product react via either nitration to dinitrocompound (Ar(NO2)2) or via oxidative demethylation to nitro-p- quinone (Q). As such, the competition between the nitration, polynitration and oxidative dealkylation is effectively modulated by the added nitric acid and the alkyl-substituted p-dimethoxybenzenes.
- Waterlot,Haskiak,Couturier
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p. 106 - 107
(2007/10/03)
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- NADPH and ferredoxin:NADP+ oxidoreductase-dependent reduction of quinones and their reoxidation
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Molecular oxygen uptake was initiated by adding NADPH (1 mM) to the buffered medium containing 0.6 μM spinach ferredoxin:NADP+ oxidoreductase and 20 μM quinone (plastoquinone-2, decyl-plastoquinone, decyl-ubiquinone, or duroquinone). At pH 7.7 the rate of oxygen uptake was 2- to 12-fold higher during an initial phase (V1) than in a subsequent phase (V2). Except for duroquinone, the initial rate of oxygen consumption was ca. 2.7-fold higher in alkaline than in acidic medium. Ferredoxin was not essential, although it stimulated the reaction investigated. Oxygen uptake was not detectable with plastoquinone-9 or α-tocoquinone. The possible mechanisms of the NADPH and ferredoxin:NADP oxidoreductase dependent reduction of some quinones and their reoxidation are discussed.
- Bojko, Monika,Wieckowski, Stanislaw
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p. 203 - 208
(2007/10/03)
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- Oxidative demethylation of 4-methylphenols to 1,4-benzoquinones with hydrogen peroxide, catalyzed by K10 montmorillonite
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2,4,6-Trimethylphenol and pentamethylphenol react with hydrogen peroxide in the presence of K10 montmorillonite (22°C, CCl4, 2 h) to afford, respectively, 2,6-dimethyl-1,4-benzoquinone and 2,3,5,6-tetramethyl-1,4-benzoquinone. 2,6-Di-tert-butyl-4-methylphenol and 4-methylphenol do not react under the same conditions. The mechanism of this reaction is discussed.
- Bushmelev,Genaev,Shubin
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- Novel ipso-Substitution of p-Sulfinylphenols through the Pummerer-Type Reaction: A Selective and Efficient Synthesis of p-Quinones and Protected p-Dihydroquinones
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The treatment of p-sulfmylphenols 3a-q with trifluoroacetic anhydride caused a Pummerer-type reaction on aromatic rings and concomitant desulfurization to give mixtures of the corresponding p-dihydroquinones 9 and p-quinones 10, which were subsequently oxidized under mild conditions to provide high yields of p-quinones 10. On the other hand, the treatment of p-(phenylsulfinyl)-phenyl ethers 6 with trifluoroacetic anhydride in the presence of styrene caused the direct ipso-substitution of the sulfinyl groups into trifluoroacetoxy groups, giving the protected dihydroquinones 14 in high yields. Both types of reactions were generally completed below room temperature within 1 h and compatible with various functional groups such as the allyl, carbonyl, ester, amide, and silyloxy groups. The preparation of the p-sulfmylphenols 3 and the silyl ethers 6 is also described through p-specific thiocyanation of phenols followed by the Grignard reaction and oxidation.
- Akai, Shuji,Takeda, Yoshifumi,Iio, Kiyosei,Takahashi, Kenji,Fukuda, Nobuhisa,Kita, Yasuyuki
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p. 5526 - 5536
(2007/10/03)
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- Catalytic Activities of CuSO4/Al2O3 in Dehydrogenation of Arenes by Dioxygen
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The oxidation reactions of hydroquinones, 2-naphthols, or 2,6-di-tert-butylphenol efficiently occurred by catalysis with alumina-supported copper(II) sulfate to give the corresponding benzoquinones, 1,1'-bi-2-naphthols, and 4,4'-diphenoquinone, respectively, in good yields.The synthetic potentiality of the catalytic reactions was demonstrated by easy isolation of the final products using only filtration and solvent evaporation as well as by application to large-scale syntheses of the benzoquinones and binaphthols.The catalysis with alumina-supported copper(II) sulfate was also applied to the oxidative intramolecular coupling of 5,5'-diacenaphthene to the corresponding perylene compound.
- Sakamoto, Takaaki,Yonehara, Hisatomo,Pac, Chyongjin
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p. 3194 - 3199
(2007/10/03)
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- Isolation of the quinone mono O,S-acetal intermediates of the aromatic pummerer-type rearrangement of p-sulfinylphenols with 1-ethoxyvinyl esters
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A versatile synthetic building block and evidence for the mechanism of the Pummerer-type rearrangement have been obtained in the form of the acetal intermediate B, isolated in the reaction of p-sulfinylphenols 1 to p-quinones 2 induced by acid anhydrides. Thus, a method is now also available for the efficient preparation of quinone monoacetals under nonoxidative conditions.
- Kita,Takeda,Matsugi,Iio,Gotanda,Murata,Akai
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p. 1529 - 1531
(2007/10/03)
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- Some recent advances in Pummerer-type reactions
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A highly enantiomeric excess in an asymmetric Pummerer-type rearrangement of chiral, non-racemic sulfoxides using O-silylated ketene acetal and the first successful Pummerer-type rearrangement on aromatic rings, are described.
- Kita, Yasuyuki
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p. 145 - 164
(2007/10/03)
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- Hydrogen-bonding and protonation effects in electrochemistry of quinones in aprotic solvents
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Hydrogen-bonding and protonation are fundamental factors controlling potentials and mechanisms in the reduction of quinones. These are studied systematically in benzonitrile, acetonitrile, and dimethylsulfoxide solutions by cyclic voltammetry of a series of quinones of increasing basicity (chloranil to duroquinone in the presence of hydroxylic additives of increasing hydrogen-bonding power (tert-butyl alcohol to hexafluoro-2- propanol) or acidity (trifluoroacetic acid). Electrochemical effects are demonstrated over the complete interaction range, from hydrogen bonding of reduced dianions to protonation of unreduced quinones. With increasing concentrations of additives, three clearly different types of electrochemical behavior are observed for weakly (I), moderately (II) and strongly (III) interacting quinone-additive pairs, as follows: (I) Two well-separated reduction waves, corresponding to formation of quinone mono- and dianions, shift positively, with no loss of reversibility. The second wave is smaller, shifts more strongly, and finally merges with the first. The relative heights of the waves remain constant. (II) The positive shift is accompanied by increasing height of the first peak and broadening and irreversibility of the second wave. (III) One or even two, more positively shifted, new prior waves appear, together with a new anodic wave. In interpreting these phenomena, the role of hydrogen-bonding is clearly distinguished from protonation on the basis of pK(a) values of relevant species, effects of solvent variation, magnitude of potential shifts, and the onset of irreversibility. Type I behavior is attributed to stabilization by hydrogen-bonding of mono- and dianion reduction products; the number of bonds per quinone ion and bonding equilibrium constants are estimated from the shifts in peak potentials with additive concentration. These results are supported by simulating the experimental cyclic voltammograms using these parameters. Type III behavior is assigned to initial hydrogen-bonding or protonation of the quinones. Type II is attributed to a reduction mechanism involving disproportionation of primary radicals, assisted by hydrogenbonding or protonation of the dianion.
- Gupta, Neeraj,Linschitz, Henry
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p. 6384 - 6391
(2007/10/03)
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- An Efficient Synthesis of p-Quinones utilizing a Novel Pummerer-type Rearrangement of p-Sulfinylphenols
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Treatment of the p-sulfinylphenol derivatives 1 and 5 with trifluoroacetic anhydride causes a Pummerer-type rearrangement on aromatic rings and concomitant desulfurization to give 1:1 mixtures of the corresponding p-quinones and p-dihydroquinones, which are subjected to mild oxidation to provide high yields of p-quinones 3 and 7.
- Akai, Shuji,Takeda, Yoshifumi,Iio, Kiyosei,Yoshida, Yutaka,Kita, Yasuyuki
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p. 1013 - 1014
(2007/10/02)
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- Oxidation of Aromatic Compounds. I. Oxidation of Methyl Derivatives of Nitrobenzene and Aniline in the System HSO3F-PbO2
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Low-temperature oxidation of methyl derivatives of nitrobenzene and aniline in the system HSO3F-PbO2 proceeds with intermediate formation of radical cations and results in replacement of hydrogen in one or two methyl groups or yields compounds of the diphenylmethane and biphenyl series.
- Rudenko, A. P.,Korovina, N. S.,Aver'yanov, S. F.
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p. 1077 - 1083
(2007/10/03)
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- Selective nitration versus oxidative dealkylation of hydroquinone ethers with nitrogen dioxide
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Various alkyl-substituted p-dialkoxybenzenes (ArH) react readily with nitrogen dioxide (NO2) in dichloromethane solution via either nitration (ArNO2) or oxidative dealkylation to quinones (Q). Spectral transients indicate that these coupled processes proceed from the dialkoxybenzene radical cation (ArH+) formed as the common reactive intermediate from electron-transfer in the disproportionated precursor [ArH, NO+]NO3-. In fast subsequent steps, ArH+ undergoes homolytic coupling with NO2 (which leads to aromatic nitration) and nucleophilic attack of NO3- (which results in oxidative dealkylation). As such, the competition between nitration and oxidative dealkylation is effectively modulated by solvent polarity and added nitrate.
- Rathore,Bosch,Kochi
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p. 6727 - 6758
(2007/10/02)
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- Novel Catalysis of Hydroquinone Autoxidation with Nitrogen Oxides
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An efficient catalytic method is described for the preparative conversion of hydroquinones to quinones with dioxygen under mild conditions.The use of the gaseous nitrogen oxide (NOx) catalyst allows a simple workup procedure for the isolation of quinones in essentially quantitative yields by merely removing the low-boiling solvent dichloromethane in vacuo.The mechanism of the catalytic autoxidation of hydroquinones is ascribed to the critical role of nitrosonium (NO(+)) in the one-electron oxidation of hydroquinone, followed by the reoxidation of the reduced nitric oxide (NO) with dioxygen.An extensive series of complex interchanges among various NOx species in nitrogen-(V), -(IV), -(III), and -(II) oxidation states, coupled with stepwise oxidation of hydroquinone via a successive series of one-electron/proton transfer, from the critical components of the catalytic cycle.
- Bosch, E.,Rathore, R.,Kochi, J. K.
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p. 2529 - 2536
(2007/10/02)
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- Convenient Preparation of Quinones via the catalytic Autoxidation of Hydroquinones with Nitrogen Oxides
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An efficient, inexpensive, catalytic method for the autoxidation of hydroquinones utilizes the gaseous (NOx) catalyst which allows a simple workup procedure for quinone isolation merely by solvent removal.
- Rathore, Rajendra,Bosch, Eric,Kochi, Jay K.
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p. 1335 - 1338
(2007/10/02)
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- Oxidation of arenes to para-quinones with hydrogen peroxide catalyzed by hexafluoroacetone hydrate
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Various aromatic hydrocarbons were oxidized with aqueous hydrogen peroxide in the presence of hexafluoroacetone hydrate as catalyst to give para-quinones and/or the ring cleavage oxidation products. The regioselective oxidation of 2-methylnaphthalene to 2-methyl-1,4-naphthoquinone (vitamin K3) was studied in detail.
- Adam,Ganeshpure
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p. 280 - 282
(2007/10/02)
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- Dimethyldioxirane oxidation of hydroquinones into quinones and 2,3-dihydroxycyclohexene-1,4-diones
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Dehydrogenation of hydroquinones 1 by dimethyldioxirane affords quinones 2 and oxygen transfer the novel 2,3-dihydroxycyclohexene-1,4-diones 3; an electron transfer mechanism is proposed for these oxidations.
- Adam,Schonberger
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- Choice of Manganese(III) Complexes for the Synthesis of 4,4'-Biphenyldiols and 4,4'-Diphenoquinones
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2,6-Disubstituted phenols are oxidized with tris(2,4-pentanedionato)manganese(III), , in glacial acetic acid to give the corresponding 4,4'-biphenyldiols in high yields, whereas similar reactions using manganase(III) acetate, , instead of quantitatively yield the corresponding 4,4'-diphenoquinones.Cross-coupling reactions of 2,6-di-t-butylphenol and other substituted phenols afford the corresponding cross-coupled 4,4'-biphenyldiols and 4,4'-diphenoquinones together with oxidation products derived from them starting phenols themselves.The advantageous use of and Mn(OAc)3> in the ubiqitous phenol coupling reaction is discussed.
- Nishino, Hiroshi,Nobuyuki, Itoh,Nagashima, Makiko,Kurosawa, Kazu
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p. 620 - 622
(2007/10/02)
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- 1,2-Migration of Perfluoroalkyl Groups in Anionotropic Rearrangement. The Acyloin Rearrangement of 4-Perfluoroalkyl-4-quinols
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Treatment of 4-perfluoroalkyl-4-quinols with a catalytic amount of potassium t-butoxide gave 2-(perfluoroalkyl)hydroquinones or 5-perfluoroalkyl-2-cyclohexene-1,4-diones in good to moderate yields depending upon the substitution pattern of the quinols.Similarly, 2-hydroxy-3-methyl-2-perfluorooctyl-1-propyl-3-pyrrolin-5-one underwent the base-induced rearrangement to afford a perfluoroalkylated succinimide derivative.
- Uno, Hidemitsu,Yayama, Ayumi,Suzuki, Hitomi
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p. 1165 - 1168
(2007/10/02)
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- Oxidation of Methoxy- and/or Methyl-Substituted Benzenes and Naphthalenes to Quinones and Phenols by H2O2 in HCOOH
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The oxidation of a number of arenes (methoxybenzenes, methylbenzenes, and naphthalenes) to quinones and phenols by H2O2 in HCOOH has been examined.Methoxybenzenes were much more easily oxidized to p-benzoquinones than methylbenzenes (e.g., 1,3,5-trimethoxybenzene was oxidized to 2,6-dimethoxy-p-benzoquinone in a 75percent yield and 1,2,4-trimethylbenzene to 2,3,5-trimethyl-p-benzoquinone in a 16percent yield).Electron-withdrawing substituents, such as nitro, cyano, and chloro groups, lowered the conversion of reactants and changed the product selectivity from quinones to phenols.Methoxybenzonitriles were oxidized to corresponding phenols in a moder ate yield (e.g., 2,6-dimethoxybenzonitrile to 3-hydroxy-2,6-dimethoxybenzonitrile in a 39percent yield and a 64percent selectivity).
- Orita, Hideo,Shimizu, Masao,Hayakawa, Takashi,Takehira, Katsuomi
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p. 1652 - 1657
(2007/10/02)
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- Efficient Preparation of Some Biologically Active Substances from Natural and Nonnatural Aromatic Compounds by m-Chloroperbenzoic Acid Oxidation
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Six naturally occurring aromatic terpenoids and six nonnatural aromatic compounds were oxidized by m-chloroperbenzoic acid in chloroform to give 1,2- and 1,4-quinones or hydroxylated products in which vitamin K1, insecticidal, piscicidal, and antifungal compounds were included.The present method is advantageous for obtaining different types of natural or nonnatural aromatic products having biological activity from the starting aromatic compounds in a one-step reaction.
- Asakawa, Yoshinori,Matsuda, Reiko,Tori, Motoo,Sono, Masakazu
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p. 5453 - 5457
(2007/10/02)
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- FUNCTIONAL GROUP OXIDATION USING SODIUM PERBORATE
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Sodium perborate in acetic acid is an effective reagent for the oxidation of anilines to nitroarenes and of sulphides to either sulphoxides or sulphones.It is also an excellent reagent for the oxidative deprotection of ketone dimethylhydrazones.Baeyer-Villiger oxidation of ketones can be carried out with sodium perborate in either trifluoroacetic acid or acetic acid/trifluoroacetic acid mixtures, and hydroquinones and certain highly substituted phenols are smoothly converted into quinones.
- McKillop, Alexander,Tarbin, Jonathan A.
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p. 1753 - 1758
(2007/10/02)
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- REACTION OF 1,2,4-TRIMETHYLBENZENE WITH PERACETIC ACID
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The oxidation of 1,2,4-trimethylbenzene with peracetic acid leads to the formation of trimethylphenols and hydroquinones, which undergo transformations to the corresponding benzoquinones and products from oxidative cleavage of the ring.The controlling stage of the process is the electrophilic hydroxylation of 1,2,4-trimethylbenzene.
- Kharchuk, V. G.,Kolenko, I. P.,Petrov, L. A.,Gus'kova, L. M.
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p. 2071 - 2078
(2007/10/02)
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- The Oxidation of Methylbenzenes and Naphthalenes to Quinones with H2O2 in the Presence of Palladium Catalyst
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Methylbenzenes and naphthalenes were oxidized to quinones with aqueous(60percent) H2O2 in acetic acid in the presence of a 0.24 wtpercent Pd(II)-sulfonated polystyrene type resin.The selectivities to quinones were higher in naphthalenes than in methylbenzenes.Among the naphthalenes used, 2-methylnaphthalene, 2,3-dimethylnaphthalene, and 2,6-dimethylnaphthalene gave 1,4-quinones in good yields (50-64percent).The increase in the reaction temperature increased the selectivity to quinones from 40percent at 20 deg C to 70percent at 70 deg C.
- Yamaguchi, Satoru,Inoue, Masami,Enomoto, Saburo
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p. 2881 - 2884
(2007/10/02)
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- Mechanistic Studies on the Oxidation of Naphthalenes and Methylbenzenes to Quinones with H2O2 in the Presence of Pd(II) Catalysts
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The oxidation of naphthalenes and methylbenzenes to quinones with aqueous 60 percent hydrogen peroxide in the presence of a 0.24 percent Pd(II)-sulfonated polystyrene-type resin catalyst was studied.The presence of electron-donating substituents on carbon-2 of naphthalenes accelerated the oxidation. A reaction path by way of hydroxylated intermediates to the quinones is proposed.By using the MINDO/3 method, quantum chemical indices such as the superdelocalizability for electrophilic species (SEr) and for radical species (SRr), and the net charge (Qr) of naphthalenes, methylbenzenes, and naphthols were calculated.The activity in the above reaction could be explained in terms of both Qr and SEr.The decrease of the selectivity was correlated with side reactions by radical species attacking the sites of largest SRr.Keywords - oxidation; hydrogen peroxide; naphthalene; methylbenzene; palladium catalyst; 1,4-naphthoquinone; sulfonated polystyrene-type resin
- Yamaguchi, Satoru,Shinoda, Hiroyuki,Inoue, Masami,Enomoto, Saburo
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p. 4467 - 4473
(2007/10/02)
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- Catalytic Oxidation of Hydroquinones and Naphthalenediols to 1,4-Quinones with H2O2 in the Presence of Chromium (VI) Oxide-Bistributyltin Oxide and an Application to Vitamin K1 Synthesis
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The oxidation of hydroquinones and naphthalenediols to 1,4-quinones was carried out in the presence of a chromium (VI) compound formed from chromium (VI) oxide and bistributyltin oxide with 30percent aqueous H2O2 in benzene-isopropyl ether at 50 deg C.The catalyst was fixed on charcoal and used for the oxidation of dihydrovitamin K1 in ethyl alcohol.
- Inoue, Masami,Uragaki, Toshitaka,Enomoto, Saburo
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p. 2075 - 2078
(2007/10/02)
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- Kinetics of Electron Transfer from Nitroaromatic Radical Anions in Aqueous solutions. Effects of Temperature and Steric Configuration
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Rate constants for electron transfer from various nitroaromatic radical anions to other nitroaromatic compounds in aqueous solutions have been determined by kinetic spectrophotometric pulse radiolysis.The rate constants were found to increase from ca. 105 to ca. 108 M-1 s-1 upon increase in driving force (ΔE) from 0 to ca. 300mV, while the activation energies decrease from ca. 6 to ca 3 kcal/mol.Nitro compounds with ortho substituents exhibit lower reduction potentials due to rotation of the nitro group away from the ring plane.Anion radicals of such compounds transfer their electrons much more slowly (k down to ca. 106 M-1 s-1) despite the apparent increase in ΔE (to ca. 550 mV).This behavior is rationalized by an increase in solvent reorganization energies around these radical anions caused by localization of the charge.In general, nitroaromatic radical anions donate electrons much more slowly than other radical anions, in reactions with similar driving forces, due to low self-exchange rates for ArNO2/ArNO-..The kinetics show no anomalies in supercooled solutions.
- Meot-Ner, Michael,Neta, P.
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p. 4648 - 4650
(2007/10/02)
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- Regioselective Side-Chain Nitration of Polymethylbenzenes Directed by an Acyl Function and Its Application to the Synthesis of Polysubstituted Phthalic Acid Derivatives
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Nitration of three types of tetramethylacetophenones and pentamethylacetophenone with fuming nitric acid in acetic anhydride was carried out.The product distributions were compared with those estimated from substituent effects.A variety of acylpentamethylbenzenes including pentamethylbenzoic acid were reacted with the nitrating system to give regioselectively 2-(nitromethyl)-3,4,5,6-tetramethylacylbenzenes.The selective nitrations of some benzoic acid derivatives followed by an alkaline treatment have been found to provide the N-hydroxyphthalimide derivatives, which a re readily converted to the phthalic anhydrides and the phthalazines.
- Keumi, Takashi,Morita, Toshio,Teramoto, Koichi,Takahashi, Hisakazu,Yamamoto, Hiroshi,et al.
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p. 3439 - 3446
(2007/10/02)
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- The Nitration of Pentamethylphenol
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Nitration of pentamethylphenol (1) with nitrogen dioxide in benzene gives the four possible 2,5,6-trinitrocyclohex-3-enones (6), (7), (8) and (9), three 4,5,6-trinitrocyclohex-2-enones (10), (11) and , the 2-hydroxy-5,6-dinitrocyclohex-3-enone (14), quinone (17) and the 4-nitro dienone (3).The fuming nitric acid nitration of pentamethylphenol (1) for 90 h gives most of these products, except that 4-nitratomethyl-2,5,6-trinitrocyclohex-3-enones (21), (22), (23) and (24) are isolated.X-ray crystal structures are reported for compounds (6), (7), (8), (10), (11), (14) and (21).
- Hartshorn, Michael P.,Robinson, Ward T.,Vaughan, John,White, Jonathon M.,Whyte, Andrew R.
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p. 1489 - 1502
(2007/10/02)
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- CERIUM CATALYZED PERSULFATE OXIDATION OF POLYCYCLIC AROMATIC HYDROCARBONS TO QUINONES
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A practical synthesis of polycyclic quinones from the parent hydrocarbons is described.The twophase oxidation of hydrocarbons was accomplished by using ammonium persulfate in the catalytic presence of cerium ammonium sulfate, silver nitrate, and sodium dodecyl sulfate.The reaction conditions and scope have been discussed in detail.
- Skarzewski, Jacek
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p. 4997 - 5000
(2007/10/02)
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- TWO-PHASE OXIDATION OF SOME AROMATIC COMPOUNDS WITH CERIUM AMMONIUM NITRATE IN THE PRESENCE OF SURFACTANTS.
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The two-phase oxidations of 3,6-dimethoxydurene and xylenes in cyclohexane solutions with the aqueous solution of cerium ammonium nitrate were carried out in the presence of cationic, nonionic, and anionic surfactants. Both cationic (ammonium salt) and nonionic (Dipodand) surfactants inhibited the reaction. The anionic surfactant (sodium dodecyl sulfate, SDS) catalyzed these oxidations. From the product distribution it was concluded that the catalytic action of SDS is due to the binding of aromatic compounds and the Ce(IV) ions to the surface of the SDS micelles. The micellar oxidant has the high oxidation potential which should allow to oxidize the comparatively nonreactive substrates.
- Skrzewski,Cichacz
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p. 271 - 274
(2007/10/02)
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- Method for preparing benzoquinones
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A method for preparing a benzoquinone represented by the general formula: STR1 where each of R1, R2, R3 and R4 is a hydrogen atom, an alkyl group or an aryl group, which comprises reacting a phenol represented by the general formula: STR2 where R1, R2 R3 and R4 are as defined above, with hydrogen peroxide in the presence of a ruthenium catalyst.
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- RUTHENIUM-CATALYZED OXIDATION OF PHENOLS WITH HYDROGEN PEROXIDE
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RuCl3 catalyzed the oxidation of trimethylphenol with 30percent H2O2 in acidic medium to give the corresponding p-bezoquinone in high yield.
- Ito, Satoru,Aihara, Kazuhisa,Matsumoto, Masakatsu
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p. 5249 - 5252
(2007/10/02)
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