- Size effect of gold nanoparticles supported on carbon nanotube as catalysts in selected organic reactions
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Carbon nanotube-supported gold nanoparticles of different sizes (diameter of 3 or 20 nm) were evaluated as catalysts in four selected organic transformations. The nanohybrids were shown to efficiently catalyze the investigated reactions, regardless of the size of the supported gold nanoparticles. However, some differences were observed as regards turnover frequency values although size effect turned out to be less significant when only gold surface atoms were considered.
- Jawale, Dhanaji V.,Gravel, Edmond,Geertsen, Valérie,Li, Haiyan,Shah, Nimesh,Kumar, Rahul,John, Jubi,Namboothiri, Irishi N.N.,Doris, Eric
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- Tert -butylhydroquinone as a spectroscopic probe for the superoxide radical scavenging activity assay of biological samples
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As a more convenient and less costly alternative to electron spin resonance (ESR) and nonspecific nitroblue tetrazolium (NBT) and cytochrome c assays of superoxide radical (SR, O2?-) detection, a novel probe, tert-butylhydroquinone (TBHQ), is introduced for SR nonenzymatically generated in the phenazine methosulfate-β-nicotinamide adenine dinucleotide (PMS-NADH) system. SR attacks both TBHQ and SR scavengers incubated in solution for 30 min where scavengers compete with TBHQ for the O2 ?- produced. TBHQ, but not its O2?- oxidation product, tert-butyl-1,4-benzoquinone (TBBQ), is responsive to the CUPRAC (cupric reducing antioxidant capacity) spectrophotometric assay. The CUPRAC absorbance of the ethyl acetate extract of the incubation solution arising from the reduction of Cu(II)-neocuproine reagent by the remaining TBHQ was higher in the presence of O2?- scavengers (due to less conversion to TBBQ), the difference being correlated to the SR scavenging activity (SRSA) of the analytes. With the use of this reaction, a kinetic approach was adopted to assess the SRSA of amino acids, vitamins, and plasma and thiol antioxidants. This assay, applicable to small-molecule antioxidants and tissue homogenates, proved to be efficient for cysteine, uric acid, and bilirubin, for which the widely used NBT test is nonresponsive. Thus, conventional problems of NBT assay arising from formazan insolubility and direct reduction of NBT by tested scavengers were overcome.
- Bekdeser, Burcu,Oezyuerek, Mustafa,Gueclue, Kubilay,Apak, Resat
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- Simple homopolymer-incarcerated gold nanoclusters prepared by self-assembled encapsulation with aluminum reagents as crosslinkers: Catalysts for aerobic oxidation reactions
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Simple homopolymer-incarcerated gold nanocluster catalysts were developed using a self-assembled encapsulation strategy. In this method, Red-Al acting as a reductant also played the role of an inter-crosslinker via the formation of tetraalkoxyaluminate with the hydroxy groups in a homopolymer. Gold nanoclusters could be immobilized at high loadings without aggregation, and high catalytic activities were observed in several aerobic oxidation reactions.
- Yasukawa, Tomohiro,Miyamura, Hiroyuki,Kobayashi, Shu
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- Some kinetic properties of deoxytyrosinase
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Passing a nitrogen stream over a preparation of oxy-tyrosinase (Eox) gives rise to the relaxed deoxy-tyrosinase form (EdR), which, under anaerobic conditions, slowly transforms into tense deoxy-tyrosinase (EdT). In the presence of oxygen, regeneration of the form Eox from EdR is rapid but from EdT it is a slow process. However, when two substrates (oxygen/o-diphenol or oxygen/monophenol) are simultaneously added, both the EdR and EdT forms rapidly revert to the active Eox form, pointing to a synergistic effect of both substrates. However, the activity obtained in the case of EdT is less than that of the native enzyme and of the enzyme that can be generated rapidly by pre-incubation with oxygen of the EdR recently formed by passage of the nitrogen stream, or that generated slowly by pre-incubating the EdT form with oxygen. Although the Vmax of the forms EdR and EdT are very similar, the Michaelis constant of the latter is higher. The kinetic properties of EdR are similar to those of the native enzyme. The behaviour of the monophenols is similar to that of the o-diphenols, although, while the latter inactivate the enzyme under anaerobic conditions, the former protect it from inactivation. The pH affects the transition from EdR to EdT, which is more rapid at pH 6.5, at which value the kinetic properties of the native enzyme and of EdT are similar and the oxygenation step in which EdT regenerates Eox is more rapid. At pH values other than 6.5, the transition of EdR to EdT takes place slowly. From a study of the effect of pH on the transition of EdR to EdT and of the re-oxygenation of EdT to Eox, the possible existence of two apparent pKas, with approximate values of 6.0 and 6.8, may be surmised. At high pH, the enzyme contains two acid/base groups carrying negative charges, which repel (pH > 6.8) or two positive charges (at pH 6.0), which also repel, while at ~pH 6.5 one positive and one negative group exists, which prevents the separation of the two copper atoms.
- Munoz-Munoz,Garcia-Molina,Garcia-Ruiz,Varon,Tudela,Garcia-Canovas,Rodriguez-Lopez
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- Aerobic Oxidation of Dihydroxyarenes Substrates Catalyzed by Polymer-Supported RuII-Pheox/Silica-Gel: A Beneficial Route for Purification of Industrial Water
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A broad class of dihydroxyarenes were easily oxidized by aerobic oxygen to quinone products in excellent yields under the catalytic effect of polymer-supported RuII-Pheox/silica-gel catalyst. By using this combined catalyst, hydroquinone and catechol derivatives with electron-donating groups were easily oxidized by molecular oxygen to quinone products in 90% to >99% yield, while in the case of electron-withdrawing group, only 70% was obtained. The biologically useful 1,4-Naphthoqinone products were obtained in 83% to 90%. The catalyst was easily obtained and reused many times without a significant decrease in reactivity. Interestingly, a sample of industrial water contaminated with phenolic compounds was subjected to aerobic oxidation by using this catalyst, and the resultant quinones were detected within one day and the catalyst was removed and reused several times with different contami-nating samples with the same efficiency. Other catalytic oxidations by using this promising catalyst were investigated.
- Abu-Elfotoh, Abdel-Moneim
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supporting information
p. 236 - 243
(2022/04/09)
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- Polyoxometalate-based supramolecular porous frameworks with dual-active centers towards highly efficient synthesis of functionalized: P -benzoquinones
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Selective oxidation of substituted phenols is an ideal method for preparing functionalized p-benzoquinones (p-BQs), which serve as versatile raw materials for the synthesis of a variety of biologically active compounds. Herein, two new polyoxometalate-based supramolecular porous frameworks, K3(H2O)4[Cu(tza)2(H2O)]2[Cu(Htza)2(H2O)2][BW12O40]·6H2O (1) and H3K3(H2O)3[Cu(Htza)2(H2O)]3[SiW12O44]·14H2O (2) (Htza = tetrazol-1-ylacetic acid), were synthesized and structurally characterized by elemental analysis, infrared spectroscopy, thermal analysis, UV-vis diffuse reflectance spectroscopy, and single-crystal X-ray and powder diffraction. The single-crystal X-ray diffraction analysis indicates that both compounds possess unique petal-like twelve-nucleated Cu-organic units composed of triangular and hexagonal metal-organic loops. In 1, the Cu-organic units are isolated and [BW12O40]5- polyoxoanions are sandwiched between staggered adjacent triangular channels in the structure. However in 2, the Cu-organic units extend into a two-dimensional layered structure, and the [SiW12O44]12- polyoxoanions occupy the larger hexagonal channels in the stacked structure. Both compounds as heterogeneous catalysts can catalyze the selective oxidation of substituted phenols to high value-added p-BQs under mild conditions (60 °C) with TBHP as the oxidant, particularly in the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethyl-p-benzoquinone (TMBQ, key intermediate in vitamin E production). Within 8-10 min, the yield of TMBQ is close to 100%, and oxidant utilization efficiency is up to 94.2% for 1 and 90.9% for 2. The turnover frequencies of 1 and 2 are as high as 5000 and 4000 h-1, respectively. No obvious decrease in the yield of TMBQ was observed after five cycles, which indicates the excellent sustainability of both compounds. Our study of the catalytic mechanism suggests that there is a two-site synergetic effect: (i) the copper ion acts as the catalytic site of the homolytic radical pathway; and (ii) the polyoxoanion acts as the active center of the heterolytic oxygen atom transfer pathway. This journal is
- An, Haiyan,Chang, Shenzhen,Chen, Yanhong,Huang, Yaohui,Luo, Huiyun,Zhu, Qingshan
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p. 8591 - 8603
(2021/11/17)
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- Benzoquinone Cocatalyst Contributions to DAF/Pd(OAc)2-Catalyzed Aerobic Allylic Acetoxylation in the Absence and Presence of a Co(salophen) Cocatalyst
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Palladium(II)-catalyzed allylic acetoxylation has been the focus of extensive development and investigation. Methods that use molecular oxygen (O2) as the terminal oxidant typically benefit from the use of benzoquinone (BQ) and a transition-metal (TM) cocatalyst, such as Co(salophen), to support oxidation of Pd0 during catalytic turnover. We previously showed that Pd(OAc)2 and 4,5-diazafluoren-9-one (DAF) as an ancillary ligand catalyze allylic oxidation with O2 in the absence of cocatalysts. Herein, we show that BQ enhances DAF/Pd(OAc)2 catalytic activity, nearly matching the performance of reactions that include both BQ and Co(salophen). These observations are complemented by mechanistic studies of DAF/Pd(OAc)2 catalyst systems under three different oxidation conditions: (1) O2 alone, (2) O2 with cocatalytic BQ, and (3) O2 with cocatalytic BQ and Co(salophen). The beneficial effect of BQ in the absence of Co(salophen) is traced to the synergistic roles of O2 and BQ, both of which are capable of oxidizing Pd0 to PdII. The reaction of O2 generates H2O2 as a byproduct, which can oxidize hydroquinone to quinone in the presence of PdII. NMR spectroscopic studies, however, show that hydroquinone is the predominant redox state of the quinone cocatalyst in the absence of Co(salophen), while inclusion of Co(salophen) maintains oxidized quinone throughout the reaction, resulting in better reaction performance.
- Kozack, Caitlin V.,Tereniak, Stephen J.,Jaworski, Jonathan N.,Li, Bao,Bruns, David L.,Knapp, Spring M. M.,Landis, Clark R.,Stahl, Shannon S.
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p. 6363 - 6370
(2021/05/29)
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- Tert-butylhydroquinone preparation method
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The invention relates to the technical field of organic synthesis, and relates to a tert-butylhydroquinone preparation method, which comprises: 1) sequentially adding 2-tert-butylphenol, a transitionmetal copper (I) cooperation compound and a solvent to a high pressure reaction kettle, introducing oxygen to achieve a specified pressure, heating and stirring to a specified temperature, and carrying out a reaction for 0.5-3 h; 2) after the reaction is finished, evaporating out the solvent, washing the residual solid with a solvent, and carrying out steam stripping to obtain 2-tert-butyl p-benzoquinone; 3) sequentially adding the 2-tert-butyl p-benzoquinone obtained in the step 1), a catalyst and a solvent into a high-pressure reaction kettle, introducing hydrogen to a specified pressure after gas exchange is completed, heating and stirring to a specified temperature, and carrying out a reaction for 0.5-3 hours; and 4) after the reaction is finished, evaporating out the solvent, and rectifying to obtain the tert-butylhydroquinone product. According to the invention, the method has the advantages of high product yield, convenient operation, cheap raw materials, economy and reliability, and is suitable for large-scale production.
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Paragraph 0025-0031
(2020/04/02)
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- Oxidative radical coupling of hydroquinones and thiols using chromic acid: One-pot synthesis of quinonyl alkyl/aryl thioethers
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An efficient, simple and practical protocol for one-pot sequential oxidative radical C-H/S-H cross-coupling of thiols with hydroquinones (HQs) and oxidation leading to the formation of quinonyl alkyl/aryl thioethers using H2CrO4was developed. This cross-coupling of thiyl and aryl radicals offers mono thioethers in good to moderate yield and works well with a wide variety of thiols. Similarly, this method works well for coupling of 2-amino thiophenol and HQs to form phenothiazine-3-ones5a-c. C-S bond formationviathioether synthesis was observed using a chromium reagent for the first time. Theoretical studies on the pharmacokinetic properties of compounds5a-crevealed that due to drug-like properties, compound5bstrongly binds with Alzheimer's disease (AD) associated AChE target sites.
- Adarsh Krishna, T. P.,Chinnasamy, Suresh,Ilangovan, Andivelu,Pandaram, Sakthivel
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p. 19454 - 19462
(2020/06/04)
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- Can Donor Ligands Make Pd(OAc)2a Stronger Oxidant? Access to Elusive Palladium(II) Reduction Potentials and Effects of Ancillary Ligands via Palladium(II)/Hydroquinone Redox Equilibria
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Palladium(II)-catalyzed oxidation reactions represent an important class of methods for selective modification and functionalization of organic molecules. This field has benefitted greatly from the discovery of ancillary ligands that expand the scope, reactivity, and selectivity in these reactions; however, ancillary ligands also commonly poison these reactions. The different influences of ligands in these reactions remain poorly understood. For example, over the 60-year history of this field, the PdII/0 redox potentials for catalytically relevant Pd complexes have never been determined. Here, we report the unexpected discovery of (L)PdII(OAc)2-mediated oxidation of hydroquinones, the microscopic reverse of quinone-mediated oxidation of Pd0 commonly employed in PdII-catalyzed oxidation reactions. Analysis of redox equilibria arising from the reaction of (L)Pd(OAc)2 and hydroquinones (L = bathocuproine, 4,5-diazafluoren-9-one), generating reduced (L)Pd species and benzoquinones, provides the basis for determination of (L)PdII(OAc)2 reduction potentials. Experimental results are complemented by density functional theory calculations to show how a series of nitrogen-based ligands modulate the (L)PdII(OAc)2 reduction potential, thereby tuning the ability of PdII to serve as an effective oxidant of organic molecules in catalytic reactions.
- Bruns, David L.,Musaev, Djamaladdin G.,Stahl, Shannon S.
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supporting information
p. 19678 - 19688
(2020/12/18)
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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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- Activated Carbon-Promoted Dehydrogenation of Hydroquinones to Benzoquinones, Naphthoquinones, and Anthraquinones under Molecular Oxygen Atmosphere
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We found that the activated carbon-molecular oxygen system promotes the conversion of hydroquinones to benzoquinones, naphthoquinones, and anthraquinones, which are often found in natural products and pharmaceuticals. In particular, the one-pot synthesis of naphthoquinones and anthraquinones involving a Diels-Alder reaction is a useful protocol for this purpose.
- Kim, Sanghun,Matsubara, Ryosuke,Hayashi, Masahiko
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p. 2997 - 3003
(2019/03/08)
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- The impact of an isoreticular expansion strategy on the performance of iodine catalysts supported in multivariate zirconium and aluminum metal-organic frameworks
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Iodine functionalized variants of DUT-5 (Al) and UiO-67 (Zr) were prepared as expanded-pore analogues of MIL-53 (Al) and UiO-67 (Zr). They were prepared using a combination of multivariate and isorecticular expansion strategies. Multivariate MOFs with a 25% iodine-containing linker was chosen to achieve an ideal balance between a high density of catalytic sites and sufficient space for efficient diffusion. Changes to the oxidation potential of the catalyst as a result of the pore-expansion strategy led to a decrease in activity with electron rich substrates. On the other hand, these larger frameworks proved to be more efficient catalysts for substrates with higher oxidation potentials. Recyclability tests for these larger MOFs showed sustained catalytic activity over multiple recycles.
- Tahmouresilerd, Babak,Moody, Michael,Agogo, Louis,Cozzolino, Anthony F.
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supporting information
p. 6445 - 6454
(2019/05/24)
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- Alkylamino and aralkylamino derivatives of avarone and its mimetic as selective agents against non-small cell lung cancer cells, their antibacterial and antifungal potential
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In this paper, the synthesis of fourteen alkylamino and arylamino derivatives of sesquiterpene quinone avarone and its model compound tert-but-ylquinone is described. Branched, cyclic, allylic and benzylic alkylamino/arylamino groups were introduced into the quinone moiety. For all the obtained derivatives, their biological activity and redox properties were studied. The cytotoxic activity of the synthesized derivatives towards multidrug resistant (MDR) human non-small cell lung carcinoma NCI-H460/R cells, their sensitive counterpart NCI-H460 and human normal keratinocytes (HaCaT) was investigated. The antimicrobial activity towards Gram-positive and Gram-negative bacteria, and fungal cultures was determined. Some of the synthesized derivatives showed selectivity for cancer cells, including MDR cells. Regarding their cell death induction potential, the most promising compounds were allylamino derivatives, preferentially triggering apoptosis, with high selectivity for cancer cells, including MDR cells. Several compounds showed promising antimicrobial activity, comparable to those of commercial antibiotic and antimycotic agents.
- Jeremi?, Marko,Dini?, Jelena,Pe?i?, Milica,Stepanovi?, Marija,Novakovi?, Irena,?egan, Dejan,Sladi?, Du?an
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p. 1193 - 1207
(2019/01/03)
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- Quinone C-H Alkylations via Oxidative Radical Processes
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A brief survey of radical additions to quinones is reported. Carboxylic acids, aldehydes, and unprotected amino acids are compared as alkyl radical precursors for the mono- or bis- C-H alkylation of several quinones. Two methods for radical initiation are discussed comparing inorganic persulfates and Selectfluor as stoichiometric oxidants. Kinetic analysis reveals dramatic differences in the rate of radical initiation depending on the identity of the radical precursor and oxidant. Synthetic strategies for efficiently producing alkyl-quinones are discussed in the context of selecting optimum radical precursors and initiators depending on quinone identity and functional groups present.
- Hamsath, Akil,Galloway, Jordan D.,Baxter, Ryan D.
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p. 2915 - 2923
(2018/06/12)
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- Hydroquinone-Based Biarylic Polyphenols as Redox Organocatalysts for Dioxygen Reduction: Dramatic Effect of Orcinol Substituent on the Catalytic Activity
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A series of 18 new biaryls has been synthesized and investigated with regard to their organocatalytic efficiency. They consist of a hydroquinone core linked to a phenol or a resorcinol moiety. It is shown that the resorcinol moiety substituted on its meta position has a strong impact on the catalytic activities of these compounds towards the reduction of dioxygen by diethylhydroxylamine (DEHA) in aqueous medium. While the derivative consisting of the two cores spaced by three methylene units is completely inactive, substitution on the hydroquinone part leads to tremendously active catalysts, especially the biaryl consisting of methoxyhydroquinone-orcinol. Two mechanisms are proposed to explain the dramatic efficiency of the novel hydroquinone-based biarylic polyphenols for the catalytic reduction of dioxygen, both considering the influence of the orcinol moiety on the semiquinone anion intermediate. As a first hypothesis, this substituent could promote its direct reduction by DEHA to regenerate the hydroquinone, which will react again to regenerate the semiquinone. On the other hand, an intramolecular hydrogen bond could enhance the reactivity of the semiquinone anion toward dioxygen by an addition–elimination mechanism. In this case, the elimination would provide the corresponding quinone but, since the reduction of the quinones by DEHA is much slower than the observed kinetics, a reduction by DEHA prior to the elimination has to be considered to generate the semiquinone anion instead of the quinone. (Figure presented.).
- Lebeuf, Rapha?l,Nardello-Rataj, Véronique,Aubry, Jean-Marie
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supporting information
p. 268 - 278
(2017/02/05)
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- Highly Selective and Efficient Ring Hydroxylation of Alkylbenzenes with Hydrogen Peroxide and an Osmium(VI) Nitrido Catalyst
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The OsVI nitrido complex, OsVI(N)(quin)2(OTs) (1, quin=2-quinaldinate, OTs=tosylate), is a highly selective and efficient catalyst for the ring hydroxylation of alkylbenzenes with H2O2 at room temperature. Oxidation of various alkylbenzenes occurs with ring/chain oxidation ratios ranging from 96.7/3.3 to 99.9/0.1, and total product yields from 93 % to 98 %. Moreover, turnover numbers up to 6360, 5670, and 3880 can be achieved for the oxidation of p-xylene, ethylbenzene, and mesitylene, respectively. Density functional theory calculations suggest that the active intermediate is an OsVIII nitrido oxo species.
- Kwong, Hoi-Ki,Lo, Po-Kam,Yiu, Shek-Man,Hirao, Hajime,Lau, Kai-Chung,Lau, Tai-Chu
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p. 12260 - 12263
(2017/09/06)
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- Catalytic asymmetric [2+2] cycloaddition between quinones and fulvenes and a subsequent stereoselective isomerization to 2,3-dihydrobenzofurans
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The catalytic enantioselective [2+2] cycloaddition between quinones and fulvenes was achieved, for the first time, by the use of a chiral copper(ii) complex catalyst. The transformation afforded a series of enantiomerically enriched [6,4,5]-tricyclic cyclobutane derivatives in good yields with excellent regio- and stereoselectivities. Furthermore, the [2+2] adducts could be easily converted into formal [3+2] adducts efficiently and stereoselectively.
- Zheng, Haifeng,Xu, Chaoran,Wang, Yan,Kang, Tengfei,Liu, Xiaohua,Lin, Lili,Feng, Xiaoming
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supporting information
p. 6585 - 6588
(2017/07/10)
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- Process for producing hydroquinone and derivates
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The present disclosure relates to an improved, environmentally friendly, process for producing compounds such as hydroquinone (benzene-1,4-diol) and its derivatives. The process can be carried out at ambient temperature and pressure using a recyclable copper catalyst and recyclable intermediate materials. The process generally entails reacting an aromatic compound such as benzene with hydrogen peroxide in the present of a pure elemental copper catalyst or a copper (I) salt catalyst to form oxidation product such as benzoquinone, and reducing the compound to hydroquinone or a hydroquinone derivative.
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Page/Page column 7
(2017/08/01)
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- Silver-Catalyzed Minisci Reactions Using Selectfluor as a Mild Oxidant
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A new method for silver-catalyzed Minisci reactions using Selectfluor as a mild oxidant is reported. Heteroarenes and quinones both participate in radical C-H alkylation and arylation from a variety of carboxylic and boronic acid radical precursors. Several oxidatively sensitive and highly reactive radical species are successful, providing structures that are challenging to access by other means.
- Galloway, Jordan D.,Mai, Duy N.,Baxter, Ryan D.
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supporting information
p. 5772 - 5775
(2017/11/10)
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- Treatment of o-tert-Butyl phenol micro-polluted water with electro-oxidation and microporous aeration: Method development, performance evaluation and mechanism study
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This study investigated the treatment of organic micro-pollutants in drinking water using a combination of electro-oxidation and microporous aeration (EOMA) technique. Results indicated that microporous aeration enhanced the turbulence of reaction solution and improved the efficiency of organic contaminant removal two-fold versus electro-oxidation alone. o-tert-Butyl phenol (OTBP) was used as a representative pollutant. 1600 mL OTBP solution contained 160 mg sodium sulfate and 2 mL 30 % hydrogen peroxide. When the current density was 5 mA cm-2, 1 and 2 mg L-1 o-tert-butyl phenol was removed up to 98.0 and 75.1 %, respectively. The major intermediate products included trimethylacetic acid, succinic acid and other acid. These have much less toxicity than o-tert-butyl phenol. After 30 min, the organics were mineralized completely. Electro-oxidation and microporous aeration was applied to actual source water that was contaminated by complicated organics. No toxicity was shown to algae growth after 15 min of treatment and total organic carbon was removed completely after 30 min.
- Chen
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p. 450 - 454
(2016/01/20)
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- Substituent effects in the oxidation of 2-alkyl-1,4-dialkoxybenzenes with ceric ammonium nitrate
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Increased steric size of alkyl groups and the presence of coordinating atoms on alkoxy groups have both been found to contribute to decreasing yields of diquinones upon reaction of 2-alkyl-1,4-dialkoxybenzenes with CAN. The overall hydrophilicity of the substrates does not appear to be a significant factor in determining the diquinone yield for these reactions.
- Love, Brian E.,Simmons, Alexander L.
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p. 5712 - 5715
(2016/11/29)
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- Functional models of nonheme diiron enzymes: Kinetic and computational evidence for the formation of oxoiron(IV) species from peroxo-diiron(III) complexes, and their reactIVity towards phenols and H2O2
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The reactivity of the previously reported peroxo adducts [Fe2(μ-O2)(L1)4(CH3CN)2]2+, and [Fe2(μ-O2)(L2)4(CH3CN)2]2+, (L1 = 2-(2′-pyridyl)benzimidazole and L2 = 2-(2′-pyridyl)-N-methylbenzimidazole) towards H2O2 as catalase mimics, and towards various phenols as functional RNR-R2 mimics, is described. Kinetic, mechanistic and computational studies gave direct evidence for the involvement of the (μ-1,2-peroxo)diiron(iii) intermediate in the O-H activation process via formation of low-spin oxoiron(iv) species.
- Szávuly, Miklós István,Surducan, Mihai,Nagy, Emoke,Surányi, Mátyás,Speier, Gábor,Silaghi-Dumitrescu, Radu,Kaizer, József
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supporting information
p. 14709 - 14718
(2016/10/03)
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- A dinuclear iron(II) complex bearing multidentate pyridinyl ligand: Synthesis, characterization and its catalysis on the hydroxylation of aromatic compounds
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A dinuclear iron(II) complex Fe2L2(μ2-Cl)2Cl2 (L = N,N-bis(pyridin-2-ylmethyl)prop-2-yn-1-amine) was prepared and fully characterized by UV–Vis spectroscopy, elemental analysis, electrochemical analysis and X-ray single crystal diffraction analysis. The catalytic activity of the complex was assessed for the hydroxylation of aromatic compounds by using aqueous H2O2 as an oxidant in acetonitrile. The catalytic system was applicable in a wide range of substrates including aromatic compounds with both electron-donating and electron-withdrawing substituents and showed moderate to good catalytic activity and selectivity in the oxidation reactions. Particularly, in the case of benzene the selectivity of phenol achieve to 74% with the reaction conversion of 24.8%.
- Gu, Erxing,Zhong, Wei,Ma, Hongxia,Xu, Beibei,Wang, Hailong,Liu, Xiaoming
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p. 159 - 165
(2018/03/29)
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- A Facile and Selective Procedure for Oxidation of Hydroquinones using Silica Gel Supported Catalytic Cerium(IV) Ammonium Nitrate
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A new procedure for oxidation of hydroquinones to quinones using a silica gel supported cerium(IV) ammonium nitrate-NaBrO3 reagent has been developed. This simple, easy to prepare and use, heterogeneous reagent is highly selective towards oxidation of 1,4-dihydroxybenzenes and produces high yields of quinones. Waste generated by using this procedure is minimal.
- Ali, Mohammed Hashmat,Welker, Andrea,York, Crystal
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p. 3207 - 3211
(2015/10/19)
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- Effects of reaction conditions on quinone/diquinone product ratios in the oxidation of 1,4-dimethoxybenzene derivatives with ceric ammonium nitrate
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Proper choice of reaction conditions allows formation of either the quinone or corresponding diquinone as the major product upon treatment of 2-alkyl-1,4-dimethoxybenzenes with ceric ammonium nitrate.
- Love, Brian E.,Duffy, Brian C.,Simmons, Alexander L.
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supporting information
p. 1994 - 1997
(2014/04/03)
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- Aerobic oxidation of phenols and related compounds using carbon nanotube-gold nanohybrid catalysts
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Gold nanoparticles supported on carbon nanotubes were investigated as catalysts in the aerobic oxidation of various substrates (phenols, hydroquinones, catechols, aminophenols, and thiols). The nanohybrid system compares favorably with other supported noble metal catalysts in terms of overall efficacy as it operates at room temperature, under air atmosphere (no external oxidant needed), and can readily be recycled. Coming up for air: Gold nanoparticles supported on carbon nanotubes were investigated as efficient catalysts in the catalytic aerobic oxidation of phenol-type compounds.
- Jawale, Dhanaji V.,Gravel, Edmond,Geertsen, Valerie,Li, Haiyan,Shah, Nimesh,Namboothiri, Irishi N. N.,Doris, Eric
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p. 719 - 723
(2014/03/21)
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- Quinones synthesis via hydrogen peroxide oxidation of dihydroxy arenes catalyzed by homogeneous and macroporous-polymer-supported ruthenium catalysts
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Ruthenium(II)/dimethyl phenyloxazoline (Ru(II)/dm-Pheox) complex 2a and its macroporous-polymeric-catalyst 4 were found to be very rapid and efficient catalysts in the hydrogen peroxide oxidation of 1,2- and 1,4-dihydroxy arenes. Most of the quinone products were delivered in 99% yield. The polymeric-catalyst 4 could be reused at least five times.
- Abu-Elfotoh, Abdel-Moneim,Tsuzuki, Kazuyuki,Nguyen, Tram Bao,Chanthamath, Soda,Shibatomi, Kazutaka,Iwasa, Seiji
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p. 8612 - 8617
(2013/09/12)
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- O2 activation and external substrate oxidation capability of a Co(ii)-semiquinonato complex
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The synthesis, characterization and catalytic oxidizing activity of a cobalt(ii)-semiquinonato complex with hydrotris(3,5-dimethyl-1-pyrazolyl)borate (=TpMe2) have been investigated. The cobalt(ii)-semiquinonato complex can be synthesized by two alternative routes; (i) dehydrative condensation of a cobalt(ii)-hydroxo complex with 3,5-di-tert-butylcatechol and following O 2 oxidation, or (ii) one-electron oxidation of catechol by a dinuclear cobalt(iii)-bis(μ-oxo) complex. The synthesized cobalt(ii)-semiquinonato complex can bind O2 at low temperatures and catalyzes the oxidation of ortho- and para-hydroquinones to the corresponding benzoquinones concomitant with the generation of hydrogen peroxide. The resulting H2O2 is utilized as an oxidant for the epoxidation of allyl alcohol catalyzed by peroxotungstate. Aerobic oxidation of benzyl alcohol to the corresponding aldehyde is also promoted by the cobalt(ii)-semiquinonato complex.
- Ikeda, Atsushi,Hoshino, Kazuya,Komatsuzaki, Hidehito,Satoh, Minoru,Nakazawa, Jun,Hikichi, Shiro
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p. 2377 - 2383
(2013/09/24)
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- μ-oxo-bridged hypervalent iodine(III) compound as an extreme oxidant for aqueous oxidations
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We have found that in aqueous oxidations the -oxo-bridged hypervalent iodine trifluoroacetate reagent 1 {[(PhI(OCOCF]} is generally more reactive than the corresponding monomeric reagent, especially toward phenolic substrates. -Oxo-bridged 1 in aqueous media thus provided dearomatized quinones 3 in excellent yields in most cases compared to conventional phenyliodine(III) diacetate and bis(trifluoroacetate), as a result of the rapid oxidation of both phenols and naphthols 2. Furthermore, the oxidation reactions proceeded even in water using water-soluble -oxo oxidant 1, which has promise for -oxo-bridged reagent 1 to become the favored reagent over hydrophobic phenyliodine(III) diacetate and bis(trifluoroacetate). Georg Thieme Verlag Stuttgart New York.
- Dohi, Toshifumi,Nakae, Tomofumi,Takenaga, Naoko,Uchiyama, Teruyoshi,Fukushima, Kei-Ichiro,Fujioka, Hiromichi,Kita, Yasuyuki
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experimental part
p. 1183 - 1189
(2012/05/19)
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- Supported sulfonic acids: Metal-free catalysts for the oxidation of hydroquinones to benzoquinones with hydrogen peroxide
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Some silica- and polystyrene-supported sulfonic acids, prepared by tethering or sol-gel techniques, were employed as metal-free heterogeneous catalysts in the oxidation of hydroquinones to the corresponding 1,4-benzoquinones, carried out with 30% aqueous hydrogen peroxide. The activity of these catalysts was tested in the model oxidation of methylhydroquinone under batch conditions: high yield and selectivity at room temperature and under environmentally friendly conditions can be achieved in the presence of SiO 2-(CH2)3-SO3H. The heterogeneous catalyst, that can be easily recovered by simply filtration, can be used for at least three cycles affording the same good results (~80% yield, ~91% selectivity).
- Maggi, Raimondo,Piscopo, Calogero G.,Sartori, Giovanni,Storaro, Loretta,Moretti, Elisa
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experimental part
p. 146 - 152
(2012/02/04)
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- IBS-catalyzed regioselective oxidation of phenols to 1,2-quinones with oxone
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We have developed the first example of hypervalent iodine(V)-catalyzed regioselective oxidation of phenols to o-quinones. Various phenols could be oxidized to the corresponding o-quinones in good to excellent yields using catalytic amounts of sodium salts of 2-iodobenzenesulfonic acids (pre-IBSes) and stoichiometric amounts of Oxone as a co-oxidant under mild conditions. The reaction rate of IBS-catalyzed oxidation under nonaqueous conditions was further accelerated in the presence of an inorganic base such as potassium carbonate (K2CO3), a phase transfer catalyst such as tetrabutylammonium hydrogen sulfate (nBu4NHSO4), and a dehydrating agent such as anhydrous sodium sulfate (Na2SO4).
- Uyanik, Muhammet,Mutsuga, Tatsuya,Ishihara, Kazuaki
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experimental part
p. 8604 - 8616
(2012/10/07)
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- An efficient catalytic oxidation of p-alkoxypenols to p-quinones using tetrabutylammonium bromide and oxone
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A catalytic oxidation of p-alkoxyphenols was developed using tetrabutylammonium bromide (TBAB) and Oxone. The reaction of p-alkoxyphenol (1) with a catalytic amount of TBAB in the presence of Oxone as a cooxidant in acetonitrile-water (2 : 1) gave the corresponding p-quinone (2) in excellent yield without special treatment.
- Yakura, Takayuki,Ozono, Ayaka,Morimoto, Kohei
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experimental part
p. 132 - 134
(2011/02/26)
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- Nitration of phenolic compounds and oxidation of hydroquinones using tetrabutylammonium chromate and dichromate under aprotic conditions
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In this work, we have reported a mild, efficient and selective method for the mononitration of phenolic compounds using sodium nitrite in the presence of tetrabutylammonium dichromate (TBAD) and oxidation of hydroquinones to quinones with TBAD in CH2Cl2. Using this method, high yields of nitrophenols and quinones were obtained under neutral aprotic conditions. Tetrabutylammonium chromate (TBAC) can also be used as oxidant at same conditions. Indian Academy of Sciences.
- Pourali, Ali Reza,Goli, Arezou
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scheme or table
p. 63 - 67
(2012/01/13)
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- Activation of the NRF2 Signaling Pathway by Copper-Mediated Redox Cycling of Para- and Ortho-Hydroquinones
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Transcription factor NF-E2 p45-related factor 2 (Nrf2) mediates adaptation to oxidants and electrophiles through up-regulating genes that contain antioxidant response elements (AREs) in their promoters. Using the stably transfected human AREc32 reporter cell line, we found that copper and other transition metals enhanced induction of ARE-driven luciferase by 2-tert-butyl-1,4-hydroquinone (tBHQ) as a result of increased oxidation to 2-tert-butyl-1,4-benzoquinone (tBQ). Following exposure to tBHQ for 30 min, ARE-luciferase activity measured after 24 hr was dependent on the presence of Cu2+. In contrast, tBQ-induced activity was Cu2+-independent. The metal-catalyzed oxidation of tBHQ to tBQ occured rapidly and stoichiometrically. Compounds that share para- or ortho-hydroquinone structures, such as catechol estrogens, dopamine, and l-DOPA, also induced ARE-driven luciferase in a Cu2+-dependent manner. Thus, the oxidation of para- and ortho-hydroquinones to quinones represents the rate-limiting step in the activation of Nrf2.
- Wang, Xiu Jun,Hayes, John D.,Higgins, Larry G.,Wolf, C. Roland,Dinkova-Kostova, Albena T.
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scheme or table
p. 75 - 85
(2010/08/05)
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- Hypervalent iodine oxidation of phenol derivatives using a catalytic amount of 4-iodophenoxyacetic acid and Oxone as a co-oxidant
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Reaction of p-substituted phenols 2 with a catalytic amount of 4-iodophenoxyacetic acid (1) and Oxone as a co-oxidant in tetrahydrofuran (THF) or 1,4-dioxane-water gave the corresponding p-quinols 3 in excellent yields. Reaction of p-dialkoxyarenes 4 in 2,2,2-trifluoroethanol- water gave the corresponding p-quinones 5 in excellent yield without purification. These reactions provide efficient and practical methods for the preparation of p-quinols and p-quinones from p-substituted phenols and p-dialkoxyarenes, respectively. This quinone synthesis was applied to synthesis of blattellaquinone (13), the sex pheromone of the German cockroach Blattella germanica.
- Yakura, Takayuki,Omoto, Masanori,Yamauchi,Tian, Yuan,Ozono, Ayaka
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experimental part
p. 5833 - 5840
(2010/09/11)
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- Catalytic hypervalent iodine oxidation using 4-iodophenoxyacetic acid and oxone: oxidation of p-alkoxyphenols to p-benzoquinones
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A catalytic hypervalent iodine oxidation of p-alkoxyphenols using 4-iodophenoxyacetic acid (1a) and Oxone was developed. Reaction of p-alkoxyphenol (2) with a catalytic amount of 1a in the presence of Oxone as a co-oxidant in 2,2,2-trifluoroethanol-water (1: 2) gave the corresponding p-quinone (3) in excellent yield without special operation. The substituent effect on iodobenzene ring in the oxidation was observed; p-alkoxy is the most effective, with the series following the approximate order p-RO>p-Me, o-MeO, m-MeO>H2H. And remarkable solvent effects were observed.
- Yakura, Takayuki,Tian, Yuan,Yamauchi, Yu,Omoto, Masanori,Konishi, Tatsuya
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experimental part
p. 252 - 256
(2009/10/15)
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- Improved synthesis of diquinones
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Preparation of a series of substituted diquinones is reported. In most examples, inverse order of addition (addition of a dimethoxybenzene derivative to a CAN solution) has been found to produce higher yields of diquinones than the traditional protocol in which the oxidant is added to the arene. Georg Thieme Verlag Stuttgart.
- Love, Brian E.,Bonner-Stewart, Jeffrey,Forrest, Lori A.
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body text
p. 813 - 817
(2009/06/19)
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- Chemoselective oxidation of benzylic alcohols and hydroquinones with bis-(2,4,6-trimethylpyridinium) dichromate (BTMPDC) as an efficient and new oxidizing agent
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A simple, efficient, and chemoselective oxidation of benzylic alcohols to the corresponding aldehydes and ketones and also hydroquinones to the benzoquinones using bis-(2,4,6-trimethylpyridinium) dichromate (BTMPDC) in acetonitrile is described. A good range of primary and secondary benzylic alcohols and a limited range of hydroquinones were selectively oxidized under reflux conditions in reasonable yields.
- Shiri, Lotfi,Ghorbani-Choghamarani, Arash
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experimental part
p. 492 - 498
(2009/09/25)
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- Redox active donor-substituted punicin derivatives
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The redox active plant material punicin from Punica granatum, 2-hydroxy-1-(pyridinium-1-yl)-5-olate, and some derivatives were modified by substitution with 2-oxochromen-4-olate moieties to give donor-substituted molecules which form distinct types of atropisomeric mesomeric betaines and tetrapolar substances. Oxidation to new negatively-charged solvatochromic quinones was achieved on treatment of these betaines with CAN, taking advantage of the stabilizing properties of the electron-donating 2-oxochromen-4-olate partial structure. The quinones can be employed in model redox reactions. Cyclovoltametric studies have been performed.
- Albrecht, Marcel,Schneider, Oliver,Schmidt, Andreas
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experimental part
p. 1445 - 1453
(2009/12/04)
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- Synthesis of 2,5-Diaminoquinones by one-pot copper-catalyzed aerobic oxidation of hydroquinones and addition reaction of amines
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The aerobic oxidation of various hydroquinones was achieved by using copper nanoparticles entrapped in aluminum oxyhydroxide [Cu/ AlO(OH)] at room temperature. Furthermore, 2,5diamino-1,4-benzoquinones were synthesized directly from hydroquinone and amines by a one-pot procedure consisting of the copper-catalyzed aerobic oxidation of hydroquinones and the double addition of amines to the resulting quinones.
- Kim, Sungjin,Kim, Daehwan,Park, Jaiwook
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experimental part
p. 2573 - 2578
(2009/12/29)
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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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- α-Naphthyltriphenylphosphonium peroxodisulfate: A selective and regenerable reagent for oxidation of organic compounds
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Alcohols, hydroquinones, tetrahydropyranyl ethers, trimethylsilyl ethers, oximes, semicarbazones, and phenylhydrazones were efficiently converted to the corresponding carbonyl compounds using α-naphthyltriphenylphosphonium peroxodisulfate (NTPPPODS) in acetonitrile at reflux conditions. This reagent could be regenerated and reused, which represents significant advantages over the known reagents. Copyright Taylor & Francis Group, LLC.
- Lakouraj, Moslem Mansour,Tajbakhsh, Mahmood,Ramzanian-Lehmali, Farhad
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scheme or table
p. 1388 - 1395
(2009/05/07)
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- Ethylenebis(N-methylimidazolium) chlorochromate (EBMICC): A new selective and mild reagent for oxidation of alcohols, hydroquinones and trimethylsilyl ethers
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The ethylenebis(N-methylimidazolium) chlorochromate was prepared by addition of N-methylimidazole to 1,2-dibromoethane to form the corresponding dibromide salt and subsequent treatment of this salt with CrO3 in 6N HCl solution. It is a stable yellow-orange solid which selectively oxidized benzylic and allylic alcohols, hydroquinones and trimethylsilyl ethers in refluxing acetonitrile. Oxidation of alcohols was also examined under solvent-free conditions and showed much better yields of the corresponding carbonyls in a very short reaction time when compared with the conventional method.
- Hosseinzadeh, Rahman,Tajbakhsh, Mahmood,Khaledi, Hamid
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scheme or table
p. 239 - 243
(2009/04/06)
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- Novel reactivity of side-on (disulfido)dicopper complexes supported by bi- and tridentate nitrogen donors: Impact of axial coordination
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(Figure Presented) What a difference a ligand makes: A comparison of the reactivity of the two complexes shown (Cu green, S yellow, N blue, O red, F pink, C gray) has revealed new redox processes previously unseen for copper-sulfur complexes. Furthermore, intriguing supporting-ligand effects on the properties of (disulfido)dicopper cores are uncovered.
- Bar-Nahum, Itsik,York, John T.,Young Jr., Victor G.,Tolman, William B.
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p. 533 - 536
(2008/09/21)
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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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- Catalytic hypervalent iodine oxidation of p-dialkoxybenzenes to p-quinones using 4-iodophenoxyacetic acid and Oxone
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A catalytic hypervalent iodine oxidation of p-dialkoxybenzenes using 4-iodophenoxyacetic acid (1) and 2KHSO5·KHSO 4·K2SO4 (Oxone) was developed. Reaction of p-dialkoxybenzenes (2) with a catalytic amount of 1 in the presence of Oxone as a co-oxidant in 2,2,2-trifluoroethanol-water (1:2) gave the corresponding p-quinones (3) in excellent yields without purification. This procedure was applied to synthesis of blattellaquinone (9), the sex pheromone of the German cockroach, Blattella germanica.
- Yakura, Takayuki,Yamauchi, Yu,Tian, Yuan,Omoto, Masanori
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experimental part
p. 1632 - 1634
(2009/09/28)
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- Oxidative deprotection of trimethylsilyl ethers to the corresponding carbonyl compounds using cetyltrimethylammonium peroxodisulfate
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Cetyltrimethylammonium peroxodisulfate (CTA)2S2O8 was quantitatively prepared and used for the oxidation and deprotection of trimethylsilyl ethers to the corresponding carbonyl compounds in acetonitrile. Selective oxidation of allylic or benzylic trimethylsilyl ethers in the presence of saturated alkyl trimethylsilyl ethers were also achieved. This new reagent is more efficient and has several advantages over similar oxidants in terms of the amount of oxidant, short reaction time, simple work up, and high yield. Copyright Taylor & Francis Group, LLC.
- Tajbakhsh, Mahmoud,Alinezhad, Heshmatollah,Urimi, Azade Geran
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scheme or table
p. 1447 - 1454
(2009/04/10)
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