- Hetero Diels-Alder reactions of 1-acetylamino- and 1-dimethylamino-1- azadienes with benzoquinones
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Treatment of bromobenzoquinone with 2 equiv. of a 1-dimethylamino-1- azadiene afforded mixtures of the corresponding 1,8-diaza-9,10-anthraquinone and 1,5-diaza-9,10-anthraquinone. Double hetero Diels-Alder reactions between 1-dimethylamino-1-azadienes and
- Pérez, José María,López-Alvarado, Pilar,Avenda?o, Carmen,Menéndez, J. Carlos
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Read Online
- Synthesis of bromo-conduritol-B and bromo-conduritol-C as glycosidase inhibitors
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For the synthesis of bromo-conduritol-B skeleton, bromo-1,4-benzoquinone was subjected to bromination followed by the reduction of the carbonyl groups with NaBH4. Substitution of bromides bonded to sp3-hybridized carbon atoms with AgOAc gave the bromo-conduritol-B tetraacetate in high yield. For the construction of bromo-conduritol-C skeleton, 2,2-dimethyl-3a,7a-dihydro-1,3-benzodioxole was used as the starting material. Photooxygenation of the diene unit gave an unsaturated bicyclic endoperoxide. Bromine was incorporated into the molecule by the addition of bromine to the double bond. Opening of the peroxide linkage followed by HBr elimination and reduction of the carbonyl group provided the conduritol-C structure in good yield. Bromo-conduritol-B exhibited strong enzyme-specific inhibition against α-glycosidase.
- Cantekin, Seda,Baran, Arif,Caliskan, Rasit,Balci, Metin
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Read Online
- Oxidative Dearomatization of Phenols and Polycyclic Aromatics with Hydrogen Peroxide Triggered by Heterogeneous Sulfonic Acids
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We report herein a method for the oxidative dearomatization of phenols and bare polycyclic arenes into the corresponding quinoid derivatives using hydrogen peroxide. The reaction is catalyzed by sulfonic acids and best results were achieved using heterogenized species. The best results using phenols were achieved using a hybrid material, namely a perfluorinated polymer functionalized with sulfonic acid groups supported on silica. The dearomatization of polycyclic aromatic hydrocarbons performed better using the polymeric acid catalyst. These methods operate under mild conditions, using mild and benign oxidants and thus minimizing the formation of waste.
- Pancrazzi, Francesco,Maestri, Giovanni,Maggi, Raimondo,Viscardi, Rosanna
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supporting information
p. 5407 - 5414
(2021/10/25)
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- Strategies towards potent trypanocidal drugs: Application of Rh-catalyzed [2?+?2?+?2] cycloadditions, sulfonyl phthalide annulation and nitroalkene reactions for the synthesis of substituted quinones and their evaluation against Trypanosoma cruzi
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Rhodium-catalyzed [2 + 2 + 2] cycloadditions, sulfonyl phthalide annulations and nitroalkene reactions have been employed for the synthesis of 56 quinone-based compounds. These were evaluated against Trypanosoma cruzi, the parasite that causes Chagas disease. The reactions described here are part of a program that aims to utilize modern, versatile and efficient synthetic methods for the one or two step preparation of trypanocidal compounds. We have identified 9 compounds with potent activity against the parasite; 3 of these were 30-fold more potent than benznidazole (Bz), a drug used for the treatment of Chagas disease. This article provides a comprehensive outline of reactions involving over 120 compounds aimed at the discovery of new quinone-based frameworks with activity against T. cruzi.
- Wood, James M.,Satam, Nishikant S.,Almeida, Renata G.,Cristani, Vinicius S.,de Lima, Dênis P.,Dantas-Pereira, Luiza,Salom?o, Kelly,Menna-Barreto, Rubem F.S.,Namboothiri, Irishi N.N.,Bower, John F.,da Silva Júnior, Eufranio N.
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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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- Unusual Chemistry in an Uncatalyzed Bromate-Aniline Oscillator: Ring-Contraction Oxidation of Aniline with Pulsative CO2 Production
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The bromate-aniline oscillatory reaction was discovered 4 decades ago, but neither the detailed mechanism nor the key products or intermediates of the reaction were described. We report herein a detailed study of this reaction, which yielded new insights. We found that oscillatory oxidation of aniline by acidic bromate proceeds, to a significant extent, via a novel reaction pathway with the periodic release of carbon dioxide. Several products were isolated, and their structures, not described so far, were justified on the basis of MS and NMR. One of the main products of the reaction associated with the CO2 release route can be assigned to 2,2-dibromo-5-(phenylimino)cyclopent-3-en-1-one. A number of known compounds produced in the studied reaction, including unexpected brominated 1-phenylpyrroles and 1-phenylmaleimides, were identified by comparison with standards. A mechanism is suggested to explain the appearance of the detected compounds, based on coupling of the anilino radical with the produced 1,4-benzoquinone. We assume that the radical adduct reacts with bromine to form a cyclopropanone intermediate that undergoes a Favorskii-type rearrangement. Further oxidation and bromination steps including decarboxylation lead to the found brominated phenyliminocyclopentenones. The detected derivatives of 1-phenylpyrrole could be produced by a one-electron oxidation of a proposed intermediate 2-phenylamino-5-bromocyclopenta-1,3-dien-1-ol followed by β-scission with the abstraction of carbon monoxide. Such a mechanism is known from the combustion chemistry of cyclopentadiene. The proposed mechanism of this reaction provides a framework for understanding the observed oscillatory kinetics.
- Valent, Ivan,Pribus, Marek,Novák, Filip,Plánková, Sylvia,Bla?ko, Jaroslav,Kubinec, Róbert,Almássy, Ambroz,Filo, Juraj,Sigmundová, Ivica,Sebechlebská, Táňa,Lawson, Thuy Bich,Noszticzius, Zoltán
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p. 9669 - 9681
(2019/11/14)
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- Rhodium-catalyzed C-H bond activation for the synthesis of quinonoid compounds: Significant Anti-Trypanosoma cruzi activities and electrochemical studies of functionalized quinones
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Thirty four halogen and selenium-containing quinones, synthesized by rhodium-catalyzed C-H bond activation and palladium-catalyzed cross-coupling reactions, were evaluated against bloodstream trypomastigotes of T.?cruzi. We have identified fifteen compounds with IC50/24?h values of less than 2?μM. Electrochemical studies on A-ring functionalized naphthoquinones were also performed aiming to correlate redox properties with trypanocidal activity. For instance, (E)-5-styryl-1,4-naphthoquinone 59 and 5,8-diiodo-1,4-naphthoquinone 3, which are around fifty fold more active than the standard drug benznidazole, are potential derivatives for further investigation. These compounds represent powerful new agents useful in Chagas disease therapy.
- Jardim, Guilherme A.M.,Silva, Thaissa L.,Goulart, Marilia O.F.,de Simone, Carlos A.,Barbosa, Juliana M.C.,Salom?o, Kelly,de Castro, Solange L.,Bower, John F.,da Silva Júnior, Eufranio N.
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p. 406 - 419
(2017/05/19)
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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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- Rh-Catalyzed Reactions of 1,4-Benzoquinones with Electrophiles: C-H Iodination, Bromination, and Phenylselenation
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Under Rh-catalyzed conditions, typically electrophilic 1,4-benzoquinones exhibit nucleophilic reactivity, such that exposure to appropriate electrophiles generates products of C-H iodination, bromination, and phenylselenation. This provides a mild and general method for direct halofunctionalization, and the first method that can achieve direct C-H phenylselenation of this compound class. The scope and limitations of the new protocols are outlined, and representative derivatizations are highlighted.
- Jardim, Guilherme A. M.,Bower, John F.,Da Silva Júnior, Eufranio N.
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supporting information
p. 4454 - 4457
(2016/09/28)
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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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- 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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- 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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- BENZOFURAN-4,5-DIONES AS SELECTIVE PEPTIDE DEFORMYLASE INHIBITORS
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The instant invention provides novel benzofuran-4,5-diones and pharmaceutical compositions thereof useful for inhibiting PDF and for treating proliferative and infectious diseases. Compounds may be selective for eukaryotic (e.g., human) PDF or prokaryotic PDF
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Page/Page column 111; 112
(2010/11/18)
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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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- Silica-gel-supported ceric ammonium nitrate (CAN): A simple and efficient solid-supported reagent for oxidation of oxygenated aromatic compounds to quinones
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A silica-gel-supported heterogeneous ceric ammonium nitrate (CAN) reagent has been developed for oxidizing oxygenated aromatics to quinones in nonaqueous media. The advantages of this procedure include excellent yields, mild reaction conditions, nonaqueous media, short reaction times, and easy product isolation. Copyright Taylor & Francis Group, LLC.
- Ali, Mohammed Hashmat,Niedbalski, Melinda,Bohnert, Gary,Bryant, Daniel
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p. 1751 - 1759
(2007/10/03)
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- Oxidation of Aromatic Amines to Quinones by Iodic Acid under Microwave Irradiation in the Presence of Montmorillonite K10 and Silica Gel
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A variety of aromatic amines are oxidized to their corresponding quinones in excellent yields by supported iodic acid under microwave irradiation and solvent free conditions.
- Hashemi, Mohammed M.,Akhbari, Maryam
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p. 1561 - 1563
(2007/10/03)
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- Cobalt and Manganese Salts of p-Aminobenzoic Acid Supported on Silica Gel: A Versatile Catalyst for Oxidation by Molecular Oxygen
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A 1:1 molar ratio of the cobalt and manganese salts of p-amino benzoic acid supported on silica gel is an effective catalyst for the oxidation of various organic compounds in reasonable yields using molecular oxygen. The catalyst can be reused several times.
- Hashemi, Mohammed M.,Ahmadibeni, Yusef
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p. 411 - 418
(2007/10/03)
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- Ultrasonically activated oxidation of hydroquinones to quinones catalysed by ceric ammonium nitrate doped on metal exchanged K-10 clay
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We have accomplished the oxidation of hydroquinones to quinones in quantitative yields using catalytic quantity of ceric ammonium nitrate doped on various metal-exchanged K-10 clay, as a mild and efficient reagent, by ultrasonic activation. The exchanged cations examined were Fe3+, Cu2+, Ce4+ and K-10 clay itself. The best results were obtained using Fe3+-Mont. K-10 clay.
- Singh, Vasundhara,Sapehiyia, Varinder,Kad, Goverdhan L.
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p. 198 - 200
(2007/10/03)
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- Bromination by means of sodium monobromoisocyanurate (SMBI)
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A variety of aromatic compounds with both activating and deactivating substituents were brominated with sodium monobromoisocyanurate (SMBI) 1, diethyl ether, diethyl ether-methanesulfonic acid, trifluoroacetic acid, or sulfuric acid were employed as solvents. Thus nitrobenzene was conveniently brominated in sulfuric acid, benzene was readily monobrominated in diethyl ether-methanesulfonic acid, and phenol was selectively brominated at the ortho position under mild conditions in refluxing diethyl ether. With substituents that are easily protonated, trifluoroacetic acid may be employed as solvent in the reaction with 1, in contrast NBS was ineffective in trifluoroacetic acid. This renders 1 a superior reagent relative to NBS. In addition to aromatics, alkenes, ketones and esters were also brominated with 1. Diethyl malonate was brominated with 1 and then subjected to a Bingel reaction with NaH to afford the desired methanofullerene in reasonable yield.
- Okada, Yukihiro,Yokozawa, Masanori,Akiba, Miwa,Oishi, Kazuhiko,O-Kawa, Kyoji,Akeboshi, Tomohiro,Kawamura, Yasuo,Inokuma, Seiichi,Nakamura, Yosuke,Nishimura, Jun
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p. 2506 - 2511
(2007/10/03)
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- Synthesis of coumaran-5-OLS - New model compounds for bioantioxidants
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Based on a Heck type reaction a new access to coumaran-5-ols has been developed. The reaction, its analytical and synthetical features as well as the nature of some by-products are discussed.
- Sch?del, Uta,Habicher, Wolf D.
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p. 1049 - 1055
(2007/10/03)
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- Photoinduced electron transfer between acenaphthylene and 1,4-benzoquinones. Formation of dimers of acenaphthylene and 1 : 1-adducts and effect of excitation mode on reactivity of the charge-transfer complexes
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Photochemical reactions of acenaphthylene (ACN) with 1,4-benzoquinones (BQs) of varying reduction potentials in solution have been investigated in order to determine final products and quantum yields of the reactions and to get an insight into the factors
- Haga, Naoki,Takayanagi, Hiroaki,Tokumaru, Katsumi
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p. 734 - 745
(2007/10/03)
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- Electrocyclic ring closure of the enols of vinyl quinones. A 2H-chromene synthesis
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equation presented Thermolysis of enolizable vinyl quinones in polar, aprotic media provides 2H-chromenes. Experimental evidence supports a two-step mechanism in which enolization is followed by a thermal 6π-electrocyclic reaction of an intermediate quinone methide. Application of this method led to the total synthesis of the reputed structure of an Ageratum juvenile hormone. When enolizable vinyl quinones are the products of Stille coupling, the chromene annulation product is obtained directly.
- Parker, Kathlyn A.,Mindt, Thomas L.
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p. 3875 - 3878
(2007/10/03)
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- Oxidation of Hydroquinones and Hydroquinone Monomethyl Ethers to Quinones with tert-Butyl Hydroperoxide and Catalytic Amounts of Ceric Ammonium Nitrate (CAN)
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Mono- and bicyclic hydroquinones and hydroquinone monomethyl ethers 1, 2 are oxidized in 82-91% yield to the corresponding quinones using only 2 mol% of ceric ammonium nitrate (CAN) and 2.5 equivalents of tert-butyl hydroperoxide.
- Krohn, Karsten,Vitz, Juergen
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p. 825 - 827
(2007/10/03)
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- Aerobic oxidation of hydroquinones to quinones catalyzed by VO(acac)2
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In the presence of a catalytic amount of VO(acac)2, oxidation of hydroquinone and its derivatives with molecular oxygen at room temperature gave the corresponding quinones in moderate to high yields.
- Hwang, Der-Ren,Chu, Chang-Ying,Wang, Sheng-Kai,Uang, Biing-Jiun
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- Oxidation of Phenols to Quinones by Oxygen Catalysed by a Mixture of Cobalt and Manganese Salts of p-Aminobenzoic Acid Supported on Silica Gel
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A mixture of cobalt and manganese salts of p-aminobenzoic acid supported on silica gel catalyses the oxidation of phenols to the corresponding quinones in the presence of oxygen.
- Hashemi, Mohammed M.,Beni, Yousef Ahmadi
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p. 138 - 139
(2007/10/03)
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- Microwave induced selective bromination of 1,4-quinones and coumarins
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Microwave irradiation accelerates the bromination of 1,4-quinones and coumarins with (i) bromide adsorbed on neutral alumina in 'dry media' and (ii) with iodine monobromide on acetic acid as compared to the reactions run at room temperature. Bromination takes place selectively at active quinonoid position in 1,4-quinones and at α,β-double bond in coumarins.
- Bansal, Vandana,Kanodia, Saraswati,Thapliyal, Prakash C.,Khanna, Rajinder N.
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p. 887 - 892
(2007/10/03)
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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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- 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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- Solid state redox chemistry of hydroquinones and quinones
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Solid state ceric ammonium nitrate (CAN) oxidation of hydroquinones to the corresponding quinones, gives best results when operating with ultrasonic irradiation. Nitrogen dioxide plays a key role in these 'solid-solid' oxidations. The oxidation of hydroquinones to quinones can also be achieved in a unique 'solid-solid-solid' reaction, i.e., by using a limited amount of CAN in the presence of a full equivalent of a solid cooxidant such as KBrO3. Reduction of quinones with sodium dithionite in the solid state gives rise to the corresponding highly colored quinhydrones and, eventually, to hydroquinones.
- Morey,Saa
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p. 105 - 112
(2007/10/02)
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- Synthesis of Mercapturic Acid Derivatives of Putative Toxic Metabolites of Bromobenzene
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The synthesis and characterization of nine isomerically defined S-arylmercapturic acids of interest in connection with the metabolism of the model hepatotoxin bromobenzene is described.Included are three S-(bromophenyl)-, two S-(bromohydroxyphenyl)-, and three S-(bromodihydroxyphenyl)mercapturic acids of defined substitution pattern.In addition, several related compounds with two or no bromine atoms are described.These syntheses depend on two basic methods, 1,4-addition of various arene thiols to acetamidoacrylic acid or the 1,4-addition of N-acetyl-L-cysteine to various benzoquinone derivatives.In addition, we describe a method for efficient conversion of the mercapturic acids to thioanisole derivatives, regioisomers of which can be separed and detected at low levels by capillary gas-liquid chromatography.
- Hanzlik, Robert P.,Weller, Paul E.,Desai, Jayant,Zheng, Jiang,Hall, Larry R.,Slaughter, Donald E.
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p. 2736 - 2742
(2007/10/02)
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- Acid- and Base-Dependent Hydrolysis of N-(Sulfonatooxy)-3-bromoacetanilide: Involvement of N-(3-Bromophenyl)hydroxylamine-O-sulfonate
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N-(Sulfonatooxy)-3-bromoacetanilide (1e) undergoes hydrolysis at 80 deg C in the range pH 1.0-8.0 by acid- and base-dependent processes and by an uncatalyzed path.The uncatalyzed reaction exhibits the same characteristics as the uncatalyzed N-O bond-cleavage reactions of the more reactive N-(sulfonatooxy)acetanilides.The pH-dependent pathways involve the hydrolysis of 1e to form N-(3-bromophenyl)hydroxylamine-O-sulfonate (2).This material cannot be directly detected under the conditions of this study, but its existence can be inferred from product study and trapping data.Although 2 undergoes decomposition entirely by heterolytic N-O bond cleavage to yield nitrenium ion intermediate 14, a less reactive analogue of 2, N-(3-bromophenyl)-O-pivaloylhydroxylamine (4), apparently undergoes competitive homolytic and heterolytic N-O bond cleavage to yield both the arylamino radical 17 and the nitrenium ion 14.Both 2 and 4 serve as models for certain suspected carcinogenic metabolites of polycyclic aromatic amines and amides.
- Novak, Michael,Rovin, Lise H.,Pelecanou, Maria,Mulero, Julio J.,Lagerman, Robert K.
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p. 2002 - 2010
(2007/10/02)
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- OXIDATION OF AROMATIC AMINES WITH CHROMYL CHLORIDE - I OXYDATION OF AROMATIC PRIMARY AMINES
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The oxidation of aromatic primary amines with chromyl chloride in carbon tetrachloride or chloroform, results in the formation of intermediate solid adducts (Etard adducts) which, on hydrolysis, give azobenzenes(1), 1,4-benzoquinones(2), anilino-1,4-benzoquinones(3), 1,4-benzoquinone anils(4) and anilino-1,4-benzoquinone anils(5) in yields which depend on the position, nature and degree of substitution of the ring.
- Nallaiah, C.,Strickson, J. A.
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p. 4083 - 4088
(2007/10/02)
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- REACTION OF HYDROGEN BROMIDE WITH N-(p-TOLYL)- AND N-(p-TOLYLSULFONYL)-1,4-BENZOQUINONE MONOIMINES
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In the reaction of hydrogen bromide with N-(p-tolyl)-1,4-benzoquinone monoimines bromination of the p-tolyl fragment takes place as well as nucleophilic addition.Bromination is fully suppressed by the addition of resorcinol to the reaction mass.In the case of N-(p-tolylsulfonyl)-1,4-benzoquinone monoimine the products from the entry of two bromine atoms at the ortho position to the oxygen atom are formed sucessively.
- Toropin, N. V.,Burmistrov, K. S.,Burmistrov, S. I.,Zaichenko, N. L.
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p. 894 - 899
(2007/10/02)
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- Mechanism of the Oxidation of NADH by Quinones. Energetics of One-Electron and Hydride Routes
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The kinetics of NADH oxidation by 7 o-benzoquinones and 14 p-benzoquinones were studied by using buffered aqueous solutions and UV/vis spectroscopy.For each quinone the rate law was first order in NADH and first order in quinone.The rate constants varied from 0.0745 to 9220 M-1s-1.Variation of the pH from 6 to 8 gave no change in rate.The use of 4-D and 4,4-D2NADH revealed kinetic isotope effects.The dideutero data gave kH/kD in the range 1.6-3.1 for p-quinones and 4.2 for 3,5-di-tert-butyl-o-quinone.When p-quinones were used, the log k was a linear function of Eo for the quinone/hydroquinone monoanion (Q/QH(1-)) couple with a slope of 16.9 V-1. o-Quinones reacted about 100 times more rapidly, but the same linear relationship with a slope of 16.4 V-1 was observed.Comparisons to data for one-electron-transfer reactions indicate that such mechanisms are not involved.A hydride-transfer mechanism accommodates all the data, and rate-limiting hydrogen atom transfer followed by electron transfer cannot be ruled out.
- Carlson, Brian W.,Miller, Larry L.
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p. 479 - 485
(2007/10/02)
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- The Kinetics and Mechanisms of Additions to Olefinic Substances. Part 16. Addition of Halogens to 1,4-Benzoquinone and to 1,4-Naphthoquinone, and Dehydrohalogenation of the Resulting Adducts
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The products of acid catalysed halogenation of 1,4-benzoquinone and 1,4-naphthoquinone in acetic acid have been investigated under conditions which could lead to the formation of dichloride, dibromide, and bromochloride.The variation in ratio of bromochloride to dibromide with relative availability of bromine and chlorine as electrophile and nucleophile suggests that the first entering halogen atom is attached nucleophilically as the result of '1,4'- (rather than then '1,2'-) addition, and that the second halogen atom is then attached electrophilically.Acetate ion does not compete effectively with chloride ion in the nucleophilic stage of the reaction; and chlorine acetate does not add, even with sulphuric acid as catalyst, to 1,4-benzoquinone.The mechanistic significance of these results is discussed.The kinetics and products of solvolytic eliminations from the dihalides derived from 1,4-benzoquinone have been studied in 95percent ethanol; the effects of structure on the rate make it probable that the reactions lie towards the E1cB end of the spectrum of elimination mechanisms.
- Atkinson, Romily C.,Mare, Peter B. D. de la,Larsen, David S.
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p. 271 - 280
(2007/10/02)
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