- Reactions of peroxynitrite with N,N-dimethyl-p-toluidine and 1,4-naphthoquinone. Evidence for heterolytic cleavage of a nitrogen-oxygen bond in peroxynitrous acid
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Peroxynitrite (ONOO-) has been found to react with the title amine 1 and quinone 5 to form N-nitrosoamine 2 and 2,3-epoxide 6, respectively, in accord with the in situ generation of the nitrosonium and hydroperoxide ions as the respective reactive species.
- Nonoyama, Nobuaki,Hisatome, Kaori,Shoda, Chizuru,Suzuki, Hitomi
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Read Online
- Bioactivity profiles of cytoprotective short-chain quinones
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Short-chain quinones (SCQs) have been investigated as potential therapeutic candidates against mitochondrial dysfunction, which was largely thought to be associated with the reversible redox characteristics of their active quinone core. We recently reported a library of SCQs, some of which showed potent cytoprotective activity against the mitochondrial complex I inhibitor rotenone in the human hepatocarcinoma cell line HepG2. To better characterize the cytoprotection of SCQs at a molecular level, a bioactivity profile for 103 SCQs with different compound chemistries was generated that included metabolism related markers, redox activity, expression of cytoprotective proteins and oxidative damage. Of all the tested endpoints, a positive correlation with cytoprotection by SCQs in the presence of rotenone was only observed for the NAD(P)H:quinone oxidoreductase 1 (NQO1)-dependent reduction of SCQs, which also correlated with an acute rescue of ATP levels. The results of this study suggest an unexpected mode of action for SCQs that appears to involve a modification of NQO1-dependent signaling rather than a protective effect by the reduced quinone itself. This finding presents a new selection strategy to identify and develop the most promising compounds towards their clinical use.
- Chear, Sueanne,Feng, Zikai,Gueven, Nuri,Hemasa, Ayman L.,Nadikudi, Monila,Smith, Jason A.,Woolley, Krystel L.
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supporting information
(2021/05/31)
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- Pyrenediones as versatile photocatalysts for oxygenation reactions with: In situ generation of hydrogen peroxide under visible light
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Pyrenediones (PYDs) are efficient photocatalysts for three oxygenation reactions: Epoxidation of electron deficient olefins, oxidative hydroxylation of organoborons, and oxidation of sulfides via in situ generation of H2O2 under visible light irradiation, using oxygen as a terminal oxidant and IPA as a solvent and a hydrogen donor.
- Zhang, Yuannian,Yang, Xin,Tang, Haidi,Liang, Dong,Wu, Jie,Huang, Dejian
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supporting information
p. 22 - 27
(2020/01/13)
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- Ligand-based design, synthesis and biochemical evaluation of potent and selective inhibitors of Schistosoma mansoni dihydroorotate dehydrogenase
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Schistosomiasis ranks second only to malaria as the most common parasitic disease worldwide. 700 million people are at risk and 240 million are already infected. Praziquantel is the anthelmintic of choice but decreasing efficacy has already been documented. In this work, we exploited the inhibition of Schistosoma mansoni dihydroorotate dehydrogenase (SmDHODH) as a strategy to develop new therapeutics to fight schistosomiasis. A series of quinones (atovaquone derivatives and precursors) was evaluated regarding potency and selectivity against both SmDHODH and human DHODH. The best compound identified is 17 (2-hydroxy-3-isopentylnaphthalene-1,4-dione) with IC50 = 23 ± 4 nM and selectivity index of 30.83. Some of the new compounds are useful pharmacological tools and represent new lead structures for further optimization.
- Calil, Felipe A.,David, Juliana S.,Chiappetta, Estela R.C.,Fumagalli, Fernando,Mello, Rodrigo B.,Leite, Franco H.A.,Castilho, Marcelo S.,Emery, Flavio S.,Nonato, M.Cristina
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p. 357 - 366
(2019/02/19)
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- Method for preparing epoxide by one-pot olefin aerobic epoxidation
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The invention relates to a method for preparing an epoxide by one-pot olefin aerobic epoxidation, and belongs to the technical field of organic synthesis. An olefin, an alkyl aromatic compound and analkali are added into a solvent, or an olefin, an alkyl aromatic compound and an alkali are directly mixed; the temperature is raised to 70-160 DEG C in an air or oxygen atmosphere; reacting is carried out for 1-48 hours; and the olefin is directly oxidized into the corresponding epoxide in the presence of the alkyl aromatic compound, the alkali and air (or oxygen), wherein the yield is up to 99%.In the reaction process, the generated alkyl peroxide is generated in situ and consumed in situ, so that the concentration of the alkyl peroxide is kept at a lower level; and generated alkyl peroxy free radicals can also react with the olefin to further generate the peroxide, and efficiency is improved. The method has the advantages of simple operation, mild conditions, low raw material cost andno need of special complex equipment, and has a good industrial application prospect.
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Paragraph 0060-0061
(2020/01/03)
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- Synthesis, anti-proliferative activity evaluation and 3D-QSAR study of naphthoquinone derivatives as potential anti-colorectal cancer agents
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Colorectal cancer (CRC) is a disease with high incidence and mortality, constituting the fourth most common cause of death from cancer worldwide. Naphthoquinones are attractive compounds due to their biological and structural properties. In this work, 36 naphthoquinone derivatives were synthesized and their activity evaluated against HT-29 cells. Overall, high to moderate anti-proliferative activity was observed in most members of the series, with 15 compounds classified as active (1.73 50 2 = 0.99 and q2 = 0.625). This model allowed proposing five new compounds with two-fold higher theoretical anti-proliferative activity, which would be worthwhile to synthesize and evaluate. Further investigations will be needed to determine the mechanism involved in the effect of most active compounds which are potential candidates for new anticancer agents.
- Acu?a, Julio,Piermattey, Jhoan,Caro, Daneiva,Bannwitz, Sven,Barrios, Luis,López, Jairo,Ocampo, Yanet,Vivas-Reyes, Ricardo,Aristizábal, Fabio,Gaitán, Ricardo,Müller, Klaus,Franco, Luis
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- Significant effect of 5,10,15,20-meso-tetraarylporphyrinatoiron(III) chloride/triflate and acidic/neutral/basic imidazolium ionic liquids in catalytic oxidation of phenols
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The influence of acidic, neutral and basic ionic liquids and their binary mixture with dichloromethane on the reactivity of iron(III)porphyrins was investigated during oxidation of phenols with hydrogen peroxide catalysed by 5,10,15,20-tetraarylporphyrinatoiron(III) chloride and 5,10,15,20-tetraarylporphyrinatoiron(III) triflate. The generation of different intermediates of iron(III) porphyrin in different ILs was studied through viscosity, density, UV–Vis and 1H NMR spectroscopy. The heterolytic cleavage efficiency of (TAP)FeIII-OOH and formation of quinone using iron(III)porphyrin (TAP)FeIIICl with Cl atom as an axial ligand, is influenced by the structure of imidazolium moiety and the counteranion following the order [(CH2)4SO3HMIm]CF3COO > [Hmim]CF3COO > [bmim]TFA ?? negligible amount in [bmim]CF3SO3, [Hmim]CF3SO3, [bmim]BF4, [bmim]PF6 and [bmim]Cl. On the other hand, the heterolytic cleavage efficiency of (TAP)FeIII-OOH with iron(III)porphyrin (TAP)FeIIICF3SO3 with triflate as an axial ligand, was found in the following order [(CH2)4SO3HMIm]CF3SO3 > [Hmim]CF3SO3 > [(CH2)4SO3HMIm]CF3COO > [Hmim]CF3COO > [bmim] CF3COO > [bmim]PF6 ≈ [bmim]BF4 ≈ [bmim]CF3SO3, while epoxidation and polymerization were mainly observed in basic and neutral ILs. The reactive intermediates formed by the reaction of monooxygen donors with (TAP)FeIIICl varied with ILs, as (TAP)+?FeIV = O intermediate was dominated in acidic ILs, while (TAP)FeIV = O was formed in neutral ILs and (TAP)FeIII-OO– was formed in basic ILs.
- Ahmad, Sohail,Gautam, Renu,Singhal, Anchal,Chauhan
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p. 292 - 303
(2018/04/10)
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- Concentrated Aqueous Sodium Tosylate as Green Medium for Alkene Oxidation and Nucleophilic Substitution Reactions
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A hydrotropic solution of highly concentrated sodium tosylate (NaOTs) can be used as a recyclable medium for the environmentally benign oxidation of conjugated alkenes with H2O2. Both uncatalyzed and metal-catalyzed reactions provided the corresponding oxidation products in higher yields than in pure water or many common organic solvents.
- Sela, Tal,Lin, Xiaoxi,Vigalok, Arkadi
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p. 11609 - 11612
(2017/11/10)
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- Tetrabutylammonium Iodide Catalyzed Epoxidation of Naphthoquinone Derivatives with tert -Butyl Hydroperoxide as an Oxidant
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An efficient and environmentally benign procedure has been developed for the epoxidation of naphthoquinone derivatives by using tetrabutylammonium iodide as a catalyst and tert -butyl hydroperoxide as an oxidant in the presence of silicon dioxide. This protocol, which provides a facile base-free methodology for the synthesis of some new naphthoquinone-based epoxides, features mild reaction conditions, high yields, remarkably short reaction time, and broad substrate scope.
- Ai, Bai-Ru,Chen, Xu-Ling,Dong, Yu,Tang, Lei,Wang, Ji-Yu
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p. 4017 - 4024
(2017/08/29)
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- Ru-Catalyzed Asymmetric Hydrogenative/Transfer Hydrogenative Desymmetrization of Meso-Epoxy Diketones
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Via a strategy of asymmetric reductive desymmetrization, chiral cis-epoxy naphthoquinols with multiple contiguous stereocenters and functional groups were synthesized with excellent enantioselectivities (96-99% ee) and diastereoselectivities (8/1-15/1). A combined asymmetric hydrogenation/transfer hydrogenation mechanism was proposed based on experimental results.
- Hong, Yuping,Chen, Jianzhong,Zhang, Zhenfeng,Liu, Yangang,Zhang, Wanbin
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supporting information
p. 2640 - 2643
(2016/06/15)
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- Unprecedented role of hydronaphthoquinone tautomers in biosynthesis
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Quinones and hydroquinones are among the most common cellular cofactors, redox mediators, and natural products. Here, we report on the reduction of 2-hydroxynaphthoquinones to the stable 1,4-diketo tautomeric form of hydronaphthoquinones and their further reduction by fungal tetrahydroxynaphthalene reductase. The very high diastereomeric and enantiomeric excess, together with the high yield of cis-3,4-dihydroxy-1-tetralone, exclude an intermediary hydronaphthoquinone. Labeling experiments with NADPH and NADPD corroborated the formation of an unexpected 1,4-diketo tautomeric form of 2-hydroxyhydronaphthoquinone as a stable intermediate. Similar 1,4-diketo tautomers of hydronaphthoquinones were established as products of the NADPH-dependent enzymatic reduction of other 1,4-naphthoquinones, and as substrates for different members of the superfamily of short-chain dehydrogenases. We propose an essential role of hydroquinone diketo tautomers in biosynthesis and detoxification processes.
- Husain, Syed Masood,Schaetzle, Michael A.,Luedeke, Steffen,Mueller, Michael
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supporting information
p. 9806 - 9811,6
(2015/02/02)
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- Efficient generation of hydrogen peroxide by aerobic photooxidation of 2-propanol using anthraquinone-2-carboxylic acid and one-pot epoxidation of α,β-unsaturated ketones
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We developed an efficient method for the generation of hydrogen peroxide by aerobic photooxidation of 2-propanol using anthraquinone-2-carboxylic acid and molecular oxygen in air and visible light from fluorescent lamps. One-pot epoxidation of α,β-unsaturated ketones using the generated hydrogen peroxide is also reported.
- Cui, Lei,Furuhashi, Sohei,Tachikawa, Yuma,Tada, Norihiro,Miura, Tsuyoshi,Itoh, Akichika
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p. 162 - 165
(2013/02/21)
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- In vivo antimalarial activity of novel 2-hydroxy-3-anilino-1,4- naphthoquinones obtained by epoxide ring-opening reaction
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1,4-Naphthoquinone derivatives are known to have relevant activities against several parasites. Among the treatment options for malaria, atovaquone, a 1,4-naphthoquinone derivative, is widely applied in the treatment and prophylaxis of such disease. Based on the structure simplification of atovaquone, we designed and synthesized four novel naphthoquinoidal derivatives. The compounds were obtained by the underexplored epoxide-opening reaction of 1,4-naphthoquinone using aniline derivatives as nucleophiles. The antiplasmodial activity of the synthesized compounds was performed in vivo using Peter's 4 days suppression test. Significant parasitemia reduction and increased survival were observed for some of the compounds.
- Rezende, Lucas Cunha Dias De,Fumagalli, Fernando,Bortolin, Marraiana Schiavon,Oliveira, Marianne Garcia De,Paula, Murilo Helder De,Andrade-Neto, Valter Ferreira De,Emery, Flavio Da Silva
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p. 4583 - 4586
(2013/08/23)
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- Facile epoxidation of α,β-unsaturated ketones with cyclohexylidenebishydroperoxide
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Cyclohexylidenebishydroperoxide was successfully used as the oxygen source for the oxidation of α,β-unsaturated ketones for the first time. The corresponding epoxides were obtained in excellent yields under the Weitz-Scheffer reaction conditions.
- Jakka, Kavitha,Liu, Jinyun,Zhao, Cong-Gui
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p. 1395 - 1398
(2007/10/03)
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- Highly efficient epoxidation of electron-deficient olefins with tetrabutylammonium peroxydisulfate
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The epoxidation of α,β-unsaturated carbonyl compounds such as enones and enals was efficiently achieved with tetrabutylammonium peroxydisulfate in the presence of equimolar amounts of hydrogen peroxide and NaOH in acetonitrile or methanol at 25 °C in excellent yields. Base-sensitive substrate such as cinnamaldehyde could be successfully epoxidized in short reaction time under mild reaction conditions.
- Yang, Seung Gak,Hwang, Je Pil,Park, Min Young,Lee, Kieseung,Kim, Yong Hae
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p. 5184 - 5188
(2008/02/01)
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- Dichlororuthenium(IV) complex of meso-Tetrakis(2,6-dichlorophenyl) porphyrin: Active and robust catalyst for highly selective oxidation of arenes, Unsaturated steroids, and electron-deficient alkenes by using 2,6-dichloropyridine N-oxide
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[RuIV(2,6-Cl2tpp)Cl2], prepared in 90% yield from the reaction of [RuVI(2,6-Cl2tpp)O2] with Me3SiCl and structurally characterized by X-ray crystallography, is markedly superior to [RuIv(tmp)Cl2], [RuIV(ttp)Cl2], and [RuII(por)(CO)] (por = 2,6-Cl2tpp, F20-tpp, F28-tpp) as a catalyst for alkene epoxidation with 2,6-Cl2pyNO (2,6Cl2tpp = meso-tetrakis(2,6-dichlorophenyl)porphyrinato dianion; tmp = meso-tetramesitylporphyrinato dianion; ttp = meso-tetrakis(p-tolyl)porphyrinato dianion; F20-tpp = meso-tetrakis(pentafluorophenyl)porphyrinato dianion; F28-tpp = 2,3,7,8,12,13,17,18-octafluoro-5,10,15,20- tetrakis(pentafluorophenyl)-porphyrinato dianion). The "[Ru IV(2,6-Cl2tpp)Cl2] + 2,6-Cl 2pyNO" protocol oxidized, under acid-free conditions, a wide variety of hydrocarbons including 1) cycloalkenes, conjugated enynes, electron-deficient alkenes (to afford epoxides), 2) arenes (to afford quinones), and 3) Δ5-unsaturated steroids, Δ4-3- ketosteroids, and estratetraene derivatives (to afford epoxide/ketone derivatives of steroids) in up to 99% product yield within several hours with up to 100% substrate conversion and excellent regio- or diastereoselectivity. Catalyst [RuIv(2,6-Cl2tpp)Cl2] is remarkably active and robust toward the above oxidation reactions, and turnover numbers of up to 6.4 × 103, 2.0 × 104, and 1.6 × 104 were obtained for the oxidation of α,β-unsaturated ketones, arenes, and Δ5-unsaturated steroids, respectively.
- Zhang, Jun-Long,Che, Chi-Ming
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p. 3899 - 3914
(2007/10/03)
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- Enzymatic desymmetrization/resolution of epoxydiols derived from 1,4-naphthoquinone, 5-hydroxy-1,4-naphthoquinone and 5,8-dihydroxy-1,4- naphthoquinone
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The enzymatic desymmetrization/resolution of epoxydiols generated from the basic epoxidation and reduction of 1,4-naphthoquoinone, 5-hydroxy-1,4- naphthoquinone and 5,8-dihydroxy-1,4-naphthoquinone is described. 2,3-Epoxy-1α,2α,3α,4 α-tetrahydronaphthalene-1,4-diol and 5,8-diallyloxy-2,3-epoxy- 1α,2α,3α,4 α-tetrahydronaphthalene-1,4-diol were desymmetrized in the presence of isopropenyl acetate using Burholderia cepacia lipase and Candida antartica lipase B, respectively. An enzymatic resolution of 8-benzyloxy-2,3-epoxy-1α,2α,3 α,4α-tetrahydronaphthalene-1,4-diol using B. cepacia lipase in isopropenyl acetate is also described.
- Betts, Russell L.,Murphy, Sean T.,Johnson, Carl R.
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p. 2853 - 2860
(2007/10/03)
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- Epoxidation of quinones with urea hydrogen peroxide
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Quinones reacted with urea-hydrogen peroxide complex in the presence of a base at room temperature, to give the corresponding quinone epoxides in 22-92% yields. The advantages of this new quinone epoxidation procedure are the requirement of organic solvent media, a easily handled solid reagent and a simple workup procedure.
- Valderrama, Jaime A.,Gonzalez, M. Florencia,Torres, Cristian
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p. 2343 - 2348
(2007/10/03)
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- Efficient electrophilic and nucleophilic epoxidations utilizing a sulfonylperoxy radical and peroxysulfate species
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Reaction of superoxide anion radical (O2-. with o-nitrobenzenesulfonyl chloride yields a o-nitrobenzenesulfonyl peroxy radical with strong oxidizing ability, which is capable of oxidizing aryl methylene moieties to aryl ketones and relatively electron-rich alkenes regioselectively to epoxides. The oxidizing species is tentatively attributed to the o-nitrobenzenesulfonyl peroxy radical of structure 1. Tetrabutylammonium peroxydisulfate (TBA)2S2O8, 2) was prepared by the reaction of tetrabutylammonium hydrogen sulfate with potassium peroxydisulfate. The epoxidation of enals and enones, such as α,β-unsaturated aldehydes or ketones, was efficiently achieved with 2 in the presence of hydrogen peroxide and base in acetonitrile or in methanol at 25°C. A base-sensitive substrate, such as cinnamaldehyde, could be successfully epoxidized under mild reaction conditions and in short reaction time.
- Park, Min Young,Yang, Seung Gak,Kim, Yong Hae
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p. 431 - 436
(2007/10/03)
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- Highly efficient epoxidation of α,β-unsaturated ketones by hydrogen peroxide with a base hydrotalcite catalyst prepared from metal oxides
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The base hydrotalcite, prepared from MgO and Al2O3, acted as a highly efficient catalyst for the epoxidation of α,β-unsaturated ketones using aqueous hydrogen peroxide as an oxidant. This heterogeneous epoxidation has the advantages of a high efficiency of H2O2 utilization without organic solvents, a simple workup procedure, and reusability of the hydrotalcite catalyst.
- Honma, Takayuki,Nakajo, Michiko,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
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p. 6229 - 6232
(2007/10/03)
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- The reaction of peroxynitrite with organic molecules bearing a biologically important functionality. The multiplicity of reaction modes as exemplified by hydroxylation, nitration, nitrosation, dealkylation, oxygenation, and oxidative dimerization and cleavage
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The reactions of peroxynitrite with a variety of organic molecules which include a biologically important functionality have been examined to construct a simple model for the peroxynitrite-induced in vivo transformations as well as a chemical probe for the active species involved therein. Phenols were found to undergo hydroxylation, nitration, oxidative dimerization, and oxidation to cyclohexadienones and quinones. The ring nitration of catechol was confirmed for the first time in the in vitro reaction of peroxynitrite. Dealkylation and N-oxide formation were the major reaction modes observed for N,N-dimethyl-p-toluidine. 1,2-Phenylenediamine gave benzotriazole in high yield. The electron-deficient C-C double bond in 1,4-naphthoquinone underwent epoxidation, while the electron-rich C-C double bond in α-methylstyrene suffered oxidative cleavage to acetophenone. The activated double bond in trans-stilbene underwent oxidative cleavage and epoxidation in parallel to give benzaldehyde and trans-stilbene oxide as the major products. The triple bond in diphenylacetylene was simply oxygenated to form benzil, together with trace amounts of ring nitration products. 1-Phenylethanol, imidazole, 2′-deoxyadenosine, and 2′-deoxyguanosine were all quite slow to react, while uracil and cytosine were almost inert to peroxynitrite. The reaction modes exhibited by peroxynitrite are too widespread and complicated to explain the whole mechanistic pathway in terms of a single active species. All reaction modes observed for the peroxynitrite to date could be classified into five categories according to their types: i) electron transfer type, ii) O-electrophilic type, iii) N-electrophilic type, iv) O-nucleophilic type, and v) radical type. Some of these may compete under certain conditions. The active species involved in each of these types of reactions are as follows: i) NO+, NO2, and OH, ii) ONOOH, iii) ONOOH and NO+, iv) OOH- and ONOO-, and v) NO2 and OH.
- Nonoyama, Nobuaki,Oshima, Hiroshi,Shoda, Chizuru,Suzuki, Hitomi
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p. 2385 - 2395
(2007/10/03)
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- Epoxidation of α,β-Unsaturated Ketones Using Hydrogen Peroxide in the Presence of Basic Hydrotalcite Catalysts
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The basic layered hydrotalcites have been used as catalysts for the epoxidation of α,β-unsaturated ketones in heterogeneous reaction media using hydrogen peroxide as an oxidant. A wide variety of α,β-unsaturated ketones were oxidized to the corresponding epoxyketones in excellent yields under mild reaction conditions. For example, 2-cyclohexen-1-one gave 2,3-epoxycyclohexanone in 91% yield at 40°C for 5 h with high efficiency in hydrogen peroxide. The catalytic activity of the hydrotalcites increased as the basicity of their surfaces increased. In the case of the epoxidation of less reactive substrates, adding a cationic surfactant such as n-dodecyltrimethylammonium bromide (DTMAB) to the above oxidation system accelerated the epoxidation reaction. These hydrotalcite catalysts were easily separated from the reaction mixture and were reusable.
- Yamaguchi, Kazuya,Mori, Kohsuke,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
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p. 6897 - 6903
(2007/10/03)
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- A new catalytic and enantioselective desymmetrization of symmetrical methylidene cycloalkene oxides
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(equation presented) Chiral copper complexes of C2-symmetrical phosphoroamidites were found to be highly effective catalysts for both kinetic resolution and novel desymmetrization reactions of new methylidene epoxycycloalkanes.
- Bertozzi, Fabio,Crotti, Paolo,Macchia, Franco,Pineschi, Mauro,Arnold, Alexander,Feringa, Ben L.
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p. 933 - 936
(2007/10/03)
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- Inverse phase transfer catalysis. III.- Optimization of the epoxidation reaction of α,β-unsaturated ketones by hydrogen peroxide
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The epoxidation of chalcone using hydrogen peroxide in the presence of a base in a two-phase medium system following the so-called Inverse Phase Transfer Catalysis (IPTC) process was investigated. Careful examination of various parameters including surfactant concentration, pH, H2O2 decomposition side-reactions and epoxide ring-opening, allowed us to determine optimal experimental conditions.
- Boyer, Bernard,Hambardzoumian, Araik,Roque, Jean-Pierre,Beylerian, Norair
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p. 6147 - 6152
(2007/10/03)
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- Novel cyclic ketones for catalytic oxidation reactions
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In our effort to search for C2 symmetric and conformationally rigid chiral ketones as catalysts for asymmetric epoxidation, a series of cyclic ketones 4-10 were prepared from the corresponding diacids. Compared with acyclic ketones for epoxidation of trans-stilbene, those 9-, 10-, and 11- membered-ring cyclic ketones were found to have much higher catalytic activities, which were attributed to steric effects, electronic effects, and ring strains. By using the homogeneous acetonitrile-water solvent system, unfunctionalized olefins with various substitution patterns (with 5 mol % of ketone 9) and strongly electron-deficient olefins (with a 1:1 ketone 9:substrate ratio) were epoxidized with Oxone as terminal oxidant in 75-96% yield at room temperature and neutral pH. In addition, oxidation of alcohols (with 20 mol % of ketone 9) was carried out successfully with good isolated yields of aldehydes or ketones (75-88%).
- Yang, Dan,Yip, Yiu-Chung,Tang, Man-Wai,Wong, Man-Kin,Cheung, Kung-Kai
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p. 9888 - 9894
(2007/10/03)
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- Practical epoxidation of α,β-unsaturated ketones with tetra-n-butylammonium peroxydisulfate
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α,β-Unsaturated ketones reacted with tetra-n-butylammonium peroxydisulfate in the presence of hydrogen peroxide and base in acetonitrile at 25 °C to give the corresponding epoxides in excellent yields.
- Kim, Yong Hae,Hwang, Je Pil,Yang, Seung Gak
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p. 3009 - 3012
(2007/10/03)
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- Reaction of naphthalene and its derivatives with hydroxyl radicals in the gas phase
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Naphthalene is the most abundant polycyclic aromatic hydrocarbon (PAH) found in urban air. It is reactive in the atmosphere under ambient conditions, its chief reaction partner being the hydroxyl radical, OH·. In this work, the reactions of OH· with naphthalene, 1- and 2-naphthol, and 1- and 2-nitronaphthalene were studied in a 9.4 m3 smog chamber. Relative rates of reaction accorded well with previous studies and allowed estimates to be made of the atmospheric lifetimes of these compounds. Numerous oxidation products were identified, and mechanisms proposed for their formation were based on the further transformation of benzocyclohexadienyl radicals formed by addition of OH· to naphthalene. The naphthols and nitronaphthalenes were deduced not to be on the major reaction pathway to the more oxidized products. Because of the high reactivity of PAH in air, we suggest that priority be given to identifying and quantitating their reaction products, some of which may be relatively persistent air toxics. Naphthalene is the most abundant polycyclic aromatic hydrocarbon (PAH) found in urban air. It is reactive in the atmosphere under ambient conditions, its chief reaction partner being the hydroxyl radical, OH·. In this work, the reactions of OH· with naphthalene, 1- and 2-naphthol, and 1- and 2-nitronaphthalene were studied in a 9.4 m3 smog chamber. Relative rates of reaction accorded well with previous studies and allowed estimates to be made of the atmospheric lifetimes of these compounds. Numerous oxidation products were identified, and mechanisms proposed for their formation were based on the further transformation of benzocyclohexadienyl radicals formed by addition of OH· to naphthalene. The naphthols and nitronaphthalenes were deduced not to be on the major reaction pathway to the more oxidized products. Because of the high reactivity of PAH in air, we suggest that priority be given to identifying and quantitating their reaction products, some of which may be relatively persistent air toxics.
- Bunce, Nigel J.,Liu, Lina,Zhu, Jiang,Lane, Douglas A.
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p. 2252 - 2259
(2007/10/03)
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- Epoxidation of α,β-unsaturated ketones with sodium perborate
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α,β-Unsaturated ketones are rapidly converted to epoxyketones at room temperature in aqueous sodium perborate in the presence of a phase transfer catalyst. Organic solvents can be used to modify the rate of epoxidation.
- Straub, Thomas S.
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p. 663 - 664
(2007/10/02)
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- Competitive epoxidation and quinone formation in the dimethyldioxirane oxidation of diazoquinones as ambident nucleophiles
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In addition to the expected dimethyldioxirane (DMD) oxidation of diazoquinones 1 to their quinones 2, the corresponding epoxy quinones 3 are formed directly and not as secondary overoxidation products of the quinones 2 since the latter are persistent towards DMD under these conditions; this novel oxidation is rationalized in terms of the ambident nucleophilic nature of the diazoquinones and corroborated by MO (AMI) calculations.
- Adam, Waldemar,Hadjiarapoglou, Lazaros,Mielke, Karsten,Treiber, Alexander
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p. 5625 - 5628
(2007/10/02)
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- Thermochemical investigation of the oxygenation of vitamin K
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Discovery of a new oxygenation reaction of naphthohydroquinone anions makes possible a determination of the heat of reaction (ΔHox) of oxygen with the potassium salt derived from deprotonation of the hydroquinone form of vitamin K. From that value (-33.52 ± 0.60 kcal/mol), the heat of deprotonation of vitamin KH2 (-30.03 ± 1.20 kcal/mol), and the heat of deprotonation of water (-6.05 ± 0.3 kcal/mol), the enthalpy change for converting vitamin KH2 to vitamin K oxide is established to be -57.5 kcal/mol, in reasonable agreement with our previous estimate of -62.4 kcal/mol for the oxygenation of the parent naphthohydroquinone. Indeed, in similar fashion the heat of oxygenation of the parent naphthohydroquinone was determined to be -58.47 kcal/mol, and this permits the assignment of a heat of formation to naphthoquinone epoxide of ΔHf° = -47.6 kcal/mol. Heats of oxygenation and deprotonation of a variety of related phenols and naphthols provide perspective on cation and substitution effects. These data provide strong support for the base strength amplification mechanism for the biological action of vitamin K proposed by two of us (P.D. and S.W.H.).
- Flowers II, Robert A.,Naganathan, Sriram,Dowd, Paul,Arnett, Edward M.,Ham, Seung Wook
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p. 9409 - 9416
(2007/10/02)
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