- 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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- Photochemical nitration by tetranitromethane. Part XXVII. Adduct formation in the photochemical reaction of 4-methylanisole. Solvent and temperature effects on the regiochemistry of reaction of the radical cation of 4-methylanisole
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The photolysis of the charge-transfer complex of 4-methylanisole and tetranitroroethane in dichloromethane gives four isomcnc nitro-triniromethyl adducts, including the epimeric 1-methoxy-4-methyl-3-nitro-6-trinitromethylcyclohexa-1,4-dienes 3 and 4 and the epimeric 1-methoxy-4-methyl-6-nitro-3-trinitromethylcyclohexa-1,4-dienes 5 and 6, 4-methyl-2-trinitromethylanisole 1, 4-methyl-2-nitroanisole 2, nitrophenols 7 and 9, and 4-methyl-4-nitrocyclohexa-2,5-dienone 8. Similar reaction in acetonitrile also gives these products, with the exception of two of the adducts (3 and 4). The effect of reaction temperature on the yields of the various products indicates that they are formed either by attack of trinrtromethanide ion on the radical cation of 4-methylanisole vicinal to the methoxy group at C2 (1, 3 and 4), or by attack of trinitromethanide ipso to the methoxy group (2, 5, 6 and 8). By conducting the photolysis in dichloromethane with trifluoroacetic acid present, the trinitromethanide pathway is eliminated, and the products formed are derived from reaction between 4-methylanisole and or its radical cation and NO2. The effects of added salts Bu4N+ClO4- (TBAP) or Bu4N+C(NO2)3- (TBAT) to reactions on dichloromethane are seen as the consequences of changes in the polarity of the solvent and not to competition between ion-pair and radical-pair collapse during the reactions. By analogy with adducts 3 and 4, two adducts 16 and 17 derived from similar photolysis reactions of 4-chloroanisole are shown to be the epimeric 4-chloro-1-methoxy-3-nitro-6-trinitromethyleyclohexa-1,4-dienes It and 17 rather than nitrit(or hydroxy)-trinitromethyl adducts. The X-ray crystal Structure of 1-methoxy-4-methyl-r-3-nitro-c-6-trinitromethylcyclohexa-1,4-. diene 3 is reported. Acta Chemica Scandinavica 1996.
- Butts, Craig P.,Eberson, Lennart,Hartshorn, Michael P.,Robinson, Ward T.
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p. 122 - 131
(2007/10/03)
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- The Mechanism of Nitration of Phenol and 4-Methylphenol by Nitrogen Dioxide in Solution
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The quantitative formation of nitrophenols from phenol by reaction with nitrogen dioxide in solution involves stages, the first being the abstraction of a hydrogen atom from the hydroxyl group by NO2. and the second the reaction of the phenoxy radical formed with NO2.The first stage is ratelimiting at high .>.In the case of 4-methylphenol a similar mechanism leads to both 4-methyl-4-nitrocyclohexa-2,5-dien-1-one and 4-methyl-6-nitrocyclohexa-2,4-dien-1-one intermediates and at high .> the apparent rate of the reaction can become the conversion of the latter intermediate into 4-methyl-2-nitrophenol.
- Coombes, Robert G.,Diggle, Andrew W.,Kempsell, Stewart P.
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p. 6373 - 6376
(2007/10/02)
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- (15)N Nuclear Polarisation in Nitration and Related Reactions. Part 6. A Comparison of (15)N and (13)C CIDNP Effects in the Nitration of Phenols
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In the nitration of 4-methylphenol in acetic anhydride, the products from nitration at the 2-position and ipso-attack at the 4-position show strong emission signals in the (15)N NMR spectrum during reaction.In the same reaction, the (13)C NMR spectrum shows emission and enhanced absorption signals for the substrate and both products.The nitration of 2-methyl-6-nitrophenol under similar conditions shows similar (15)N nuclear polarisation and similar (13)C nuclear polarisation in the substrate but the polarisation in the product is complicated by the fast rearrangement of the ipso-intermediate.The pattern of nulear polarisation in these substrates identifies the phenoxy radical as one component of the radical pair generating the polarisation and accords with the accepted mechanism for nitrous acid catalysed nitration.
- Ridd, John H.,Trevellick, Susan,Sandall, John P. B.
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p. 573 - 578
(2007/10/02)
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- Formation of 4-Halo-4-nitrocyclohexa-2,5-dienones on Nitration of p-Halophenols and p-Halophenyl Acetates.
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Nitration of p-chloro-, p-fluoro-, and p-bromo-phenol or the corresponding p-halophenyl acetates at -40 deg C and below gives the 4-halo-4-nitrocyclohexa-2,5-dienones in addition to the 4-halo-2-nitrophenols.The dienones isomerize to the nitrophenols at temperatures between -40 deg C and 0 deg C.Nitration of 4-chloro-2-methylphenol or its acetate gives both 4-chloro-2-methyl-4-nitrocyclohexa-2,5-dienone and 4-chloro-6-methyl-6-nitrocyclohexa-2,4-dienone. 4-Chloro-3-methylphenol and its acetate give 4-chloro-3-methyl-4-nitrocyclohexa-2,5-dienone.
- Clewley, Robin G.,Cross, Gordon G.,Fischer, Alfred,Henderson, George N.
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p. 1299 - 1310
(2007/10/02)
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- The Nitration of 4-Methylphenol, 3,4-Dimethylphenol and 3,4,5-Trimethylphenol with Nitrogen Dioxide
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Reaction of 4-methylphenol (1a) with excess nitrogen dioxide in either benzene or dichloromethane gives the 4-nitro dienone (2a) and the 2,6-dinitrophenol (5).Similar reactions of 3,4-dimethylphenol (1b) yields the 4-nitro dienone (2b), the 2,6-dinitrophe
- Hartshorn, Michael P.,Judd, Maurice C.,Vannoort, Richard W.,Wright, Graeme J.
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p. 689 - 697
(2007/10/02)
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- FORMATION OF DIENONES ON THE REACTION OF CRESOLS, XYLENOLS, AND 2-NAPHTHOL WITH NITROGEN DIOXIDE: OBSERVATION OF KETO TAUTOMERS OF NITROPHENOLS
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Reaction of o- and p-cresol, the xylenols, and 2-naphthol with nitrogen dioxide gives nitrocyclohexadienones and nitrophenols.Secondary nitrodienones, the keto tautomers of the nitrophenols, have been observed in several cases and are intermediates in the formation of the nitrophenols.
- Fischer, Alfred,Mathivanan, N.
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p. 1869 - 1872
(2007/10/02)
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- Formation of 4-Nitrocyclohexa-2,5-dienols by Addition of Organolithium Reagents to 4-Alkyl-4-nitrocyclohexa-2,5-dienones
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Addition of methyllithium to 4-alkyl-4-nitrocyclohexa-2,5-dienones 1a-d (alkyl = Me, Et, i-Pr, t-Bu), to 2,6-dichloro- and 2,6-dibromo-4-methyl-4-nitrocyclohexa-2,5-dienone, and to 4a-nitro-2-oxo-2,4a,5,6,7,8-hexahydronaphthalene gives the corresponding dienols 2a-d, 4e and 4f, and 7g, generally as a pair of diastereomers.Addition of methyl lithioacetate to the same substrates gives dienols 8a-d, 5e and 5f, and 7h.Addition of substituted methyllithiums (XCH2Li, X = CN, CONH2, CONMe2, COMe, SMe, SPh, SOMe, SO2Me, SiMe3, PSMePh, PSPh2), 2-lithio-1,3-dithiane, or lithium phenylacetylide to 1a gives the dienols 9i-u.
- Fischer, Alfred,Sankararaman, S.
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p. 4464 - 4468
(2007/10/02)
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- ipso Nitration. XXVIII. Nitration of 4-substituted toluenes: 1,2 adducts
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Nitration of 4-acetamido, 4-chloro, and 4-methoxy-toluene in acetic anhydride gives in each case a cis 1,2 nitronium acetate adduct in adition to the nitro substitution product(s).Nitration of 4-fluorotoluene gives a pair of diastereomeric 1,4 nitronium acetate adducts and the cis 1,2 adduct.
- Fisher, Alfred,Fyles, Deborah L.,Henderson, George, N.,Mahasay, Sumit Ray
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p. 1764 - 1770
(2007/10/02)
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- ipso-Nitration: Formation of Nitronium Acetate Adducts in the Nitration of p-Acetamido-, p-Halogeno-, and p-Methoxy-toluenes, and α-p-Tolyloxyisobutyric acid
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Low-temperature nitration of the title compounds in acetic anhydride gives 1,2-nitronium acetate adducts, except p-fluorotoluene which gives both 1,2 and 1,4 adducts and α-p-tolyloxyisobutyric acid which gives a spiro adduct.
- Fischer, Alfred,Fyles, Deborah L.,Henderson, George N.
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p. 513 - 514
(2007/10/02)
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