- Efficient and Selective Oxidation of Aromatic Amines to Azoxy Derivatives over Aluminium and Gallium Oxide Catalysts with Nanorod Morphology
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Aluminium oxide and gallium oxide nanorods were identified as highly efficient heterogeneous catalysts for the selective oxidation of aromatic amines to azoxy compounds using hydrogen peroxide as environmentally friendly oxidant. This is the first report of the selective oxidation of aromatic amines to their azoxy derivatives without using transition metal catalysts. Among the tested transition-metal-free oxides, gallium oxide nanorods with small dimensions (9–52 nm length and 3–5 nm width) and fully accessible, high surface area (225 m2 g?1) displayed the best catalytic performance in terms of substrate versatility, activity and azoxybenzene selectivity. Furthermore, the catalyst loading, hydrogen peroxide type (aqueous or anhydrous), and the amount of solvent were tuned to optimise the catalytic performance, which allowed reaching almost full selectivity (98 %) towards azoxybenzene at high aniline conversion (94 %). Reusability tests showed that the gallium oxide nanorod catalyst can be recycled in consecutive runs with complete retention of the original activity and selectivity.
- Singh, Bhawan,Mandelli, Dalmo,Pescarmona, Paolo P.
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p. 593 - 601
(2019/11/13)
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- Low-temperature catalytic oxidation of aniline to azoxybenzene over an Ag/Fe2O3 nanoparticle catalyst using H2O2 as an oxidant
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An in situ modified hydrothermal synthesis of Ag/Fe2O3 nanoparticles (NPs) and studies of their catalytic activity as a simple, eco-friendly and recyclable catalyst for one-pot conversion of aniline to azoxybenzene were performed. The as-synthesized nanostructured material was characterised by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), SEM-mapping, temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherms (BET), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), ultraviolet-visible spectroscopy (UV-vis) and vibrating sample magnetometer spectroscopy (VSM). The most active and recyclable catalyst with 2-5 nm diameters of the metallic Ag particles supported on 10-50 nm Fe2O3 nanoparticles was formed with a silver loading of 1.8 wt%. A high turnover number of ~592 was achieved with 92% conversion of aniline and 94% selectivity towards the target product azoxybenzene under atmospheric conditions. The effects of various reaction parameters including the reaction time, temperature and substrate to H2O2 molar ratio were screened and studied in detail. The results reveal the role of a synergistic effect between the surface Ag nanoparticles and Fe2O3 nanospheres for high catalytic activity.
- Paul, Bappi,Sharma, Sachin K.,Adak, Shubhadeep,Khatun, Rubina,Singh, Gurmeet,Das, Dipak,Joshi, Vedant,Bhandari, Sahil,Dhar, Siddhartha Sankar,Bal, Rajaram
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p. 8911 - 8918
(2019/06/18)
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- Nb2O5 supported on mixed oxides catalyzed oxidative and photochemical conversion of anilines to azoxybenzenes
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The synthesis of novel supported niobium oxide catalysts and their application for aniline conversion to azoxybenzenes is described. The catalysts were successfully prepared by thermal decomposition of layered double hydroxides (LDHs), containing M2+ (M = Mg2+ and/or Zn2+) and Al3+ as layer cations, followed by niobium oxide incorporation employing the wetness impregnation method. These catalysts were fully characterized by both experimental techniques and theoretical calculations, and then successfully applied to the selective conversion of anilines into azoxybenzene derivatives, with up to 98% conversion and 92% isolated yield in the presence of violet light. Control experiments and DFT calculations revealed that the catalyst has a dual role in this transformation, acting both as a Lewis acid in the oxidative step and as a photocatalyst in the dimerization of the nitrosobenzene intermediate.
- De Carvalho, Gustavo Senra Gon?alves,Chagas, Luciano Honorato,Fonseca, Carla Grijó,De Castro, Pedro P?ssa,Sant'Ana, Ant?nio Carlos,Leit?o, Alexandre Amaral,Amarante, Giovanni Wilson
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supporting information
p. 5863 - 5871
(2019/04/17)
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- Synthesis of Azoxybenzenes by Reductive Dimerization of Nitrosobenzene
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Herein we report an effective and simple preparation method of substituted azoxybenzenes by reductive dimerization of nitrosobenzenes. This procedure requires no additional catalyst/reagent and can be applied to substrates with a wide range of substitution patterns.
- Chen, Yu-Feng,Chen, Jing,Lin, Li-Jen,Chuang, Gary Jing
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p. 11626 - 11630
(2017/11/10)
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- Organocatalytic oxidation of substituted anilines to azoxybenzenes and nitro compounds: Mechanistic studies excluding the involvement of a dioxirane intermediate
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An organocatalytic and environmentally friendly approach for the selective oxidation of substituted anilines was developed. Utilizing a 2,2,2-trifluoroacetophenone-mediated oxidation process, substituted anilines can be transformed into azoxybenzenes, while a simple treatment with MeCN and H2O2 leads to the corresponding nitro compounds, providing user-friendly protocols that can be easily scaled up. Various substitution patterns and functional groups were tolerated leading to products in high to excellent yields. Mechanistic studies utilizing HRMS provide clear evidence for the distinct mechanistic intermediates that are involved. This study constitutes an indirect proof excluding the involvement of a dioxirane intermediate in the green organocatalytic oxidation, utilizing 2,2,2-trifluoroacetophenone as the catalyst.
- Voutyritsa, Errika,Theodorou, Alexis,Kokotou, Maroula G.,Kokotos, Christoforos G.
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supporting information
p. 1291 - 1298
(2017/06/06)
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- Aromatic amine oxidation process for preparing aromatic liquid discharge method
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The invention relates to a preparation method for aromatic-azoxybenzene by oxidizing aromatic amine. According to the method, air or oxygen is used as an oxygen source, and aromatic amine is oxidized to be aromatic-azoxybenzene under the effect of metal oxide catalyst. The method has the advantage of high product yield and is easy to separate the catalyst.
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Paragraph 0014; 0015; 0016; 0017; 0018; 0019-0023; 0025
(2017/08/26)
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- Room temperature selective oxidation of aniline to azoxybenzene over a silver supported tungsten oxide nanostructured catalyst
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Heterogeneous catalysts comprising silver nanoparticles supported on nanostructured tungsten oxide were applied for room temperature oxidative coupling of aniline to azoxybenzene, an important chemical intermediate and a chemical of industrial interest. The catalytic protocol features high activity and selectivity to the target product azoxybenzene with a turnover number of ~368. The catalyst was characterized by XRD, XPS, ICP-AES, FT-IR, TGA, EXAFS, SEM and TEM. The silver-tungsten nanomaterial acts as an excellent catalyst for selective oxidation of aniline to azoxybenzene using H2O2 as an oxidant. An aniline conversion of 87% with 91% selectivity of azoxybenzene was achieved without the use of any external additives. Moreover, a high stability and recyclability of the catalyst is also observed under the investigated conditions. This journal is
- Ghosh, Shilpi,Acharyya, Shankha S.,Sasaki, Takehiko,Bal, Rajaram
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p. 1867 - 1876
(2015/03/18)
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- Ultrasound-accelerated selective oxidation of primary aromatic amines to azoxy derivatives with trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane catalyzed by Preyssler acid-mediated nano-TiO2
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Preyssler-type heteropolyacid supported on TiO2 nanoparticles has been explored as an efficient catalyst in selective oxidation of primary aromatic amines to azoxy derivatives using trans-3,5-dihydroperoxy-3,5-dimethyl- 1,2-dioxolane as oxidant. The reactions proceeded smoothly under mild and green ultrasound-accelerated conditions to afford the products in high yields. The catalyst recovered from the reaction mixture exhibits long-term stability with no significant drop in its catalytic activity. Graphical abstract: [Figure not available: see fulltext.].
- Azarifar, Davood,Khatami, Seyed-Mola,Najminejad, Zohreh
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p. 587 - 592
(2014/04/03)
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- Silica encapsulated magnetic nanoparticles-supported Zn(II) nanocatalyst: A versatile integration of excellent reactivity and selectivity for the synthesis of azoxyarenes, combined with facile catalyst recovery and recyclability
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A novel and highly efficient zinc based nanocatalyst has been synthesized by covalent grafting of 2-acetylpyridine on amine functionalized silica@magnetite nanoparticles, followed by metallation with zinc acetate. The resulting nano-composite was found to be highly efficient for oxidation of various aromatic amines to give azoxyarenes. The prepared nanocatalyst was characterized by Electron microscopy techniques (SEM and TEM with EDS), X-ray diffraction (XRD), vibrational sampling magnetometer (VSM), Fourier transform infrared spectroscopy (FT-IR) and atomic absorption spectroscopy (AAS) techniques. High turnover number (TON), mild reaction conditions and high selectivity for azoxyarenes with sustained catalytic activity makes present protocol worthy and highly compliant as compared to the other non-magnetic heterogeneous catalytic system. The acquisition of this nanocatalyst is also exemplified by employing the catalyst in leaching and reusability test and the results from the tests showing negligible zinc leaching and recycling was achieved multiple times just by sequestering using an external magnet.
- Sharma,Monga, Yukti
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- Gold-catalyzed cyclization/oxidative [3+2] cycloadditions of 1,5-enynes with nitrosobenzenes without additional oxidants
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Golden control: The title reaction (see scheme) proceeds with high stereocontrol to generate the heterocyclic products in good yield. Experiments to probe the mechanism were performed. Copyright
- Chen, Chun-Hao,Tsai, Yen-Ching,Liu, Rai-Shung
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supporting information
p. 4599 - 4603
(2013/05/21)
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- Ruthenium nanoparticle-catalyzed, controlled and chemoselective hydrogenation of nitroarenes using ethanol as a hydrogen source
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This communication describes a ruthenium nanoparticle-catalyzed reduction of nitroarenes giving azoxyarenes, azoarenes, or anilines in good to excellent yields using ethanol as a hydrogen source. Copyright
- Kim, Ju Hyun,Park, Ji Hoon,Chung, Young Keun,Park, Kang Hyun
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supporting information
p. 2412 - 2418
(2012/11/07)
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- Mechanosynthesis of nitrosobenzenes: A proof-of-principle study in combining solvent-free synthesis with solvent-free separations
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Mechanochemical Oxone oxidation of selected para-substituted anilines was used as a rapid and solvent-free route to nitrosobenzenes; besides avoiding bulk solvents and short reaction times, this method exploits high vapour pressures of nitrosobenzenes for the solvent-free separation of the product by sublimation, demonstrating an entirely solvent-free route to chemical synthesis and product isolation. The Royal Society of Chemistry.
- Huskic, Igor,Halasz, Ivan,Friscic, Tomislav,Vancik, Hrvoj
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supporting information
p. 1597 - 1600
(2013/02/23)
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- Oxidation of anilines with hydrogen peroxide and selenium dioxide as catalyst
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A variety of substituted anilines are selectively oxidized to afford high yields of azoxyarenes by using 30% hydrogen peroxide and selenium dioxide as catalyst in methanol at room temperature. The oxidation of 4-alkoxyanilines under the same reaction conditions furnishes the corresponding 4-alkoxy-N-(4-nitrophenyl)anilines in reasonable yields, alongside other oxidation byproducts. The structure of 4-methoxy-N-(4-nitrophenyl)aniline is elucidated by X-ray crystal structure analysis. From these results, some general aspects of the reaction pathways of aniline oxidation are discussed.
- Gebhardt, Christin,Priewisch, Beate,Irran, Elisabeth,Rueck-Braun, Karola
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scheme or table
p. 1889 - 1894
(2009/04/04)
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- Reaction of aromatic nitroso compounds with chemical models of 'thiamine active aldehyde'
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Aromatic nitroso compounds in the presence of base and 2-(α-hydroxyalkyl)-3,4-dimethylthiazolium trifluoromethanesulfonate and related salts furnish in variable yields O- and N-acyl-aryl hydroxylamines and 3,4-dimethylthiazolium trifluoromethanesulfonate. A primary kinetic isotope effect of 4.9, obtained for the appropriate 2α-deuterated thiazolium salt, points to the C2α-H bond cleavage as the rate determining step. Radical species detected by ESR were unambiguously identified as phenylhydronitroxide, but attempted trapping of the corresponding C-heterocyclic radicals by TEMPO was not successful, and substrates incorporating a potential cyclopropyl radical clock gave products with the cyclopropyl ring intact. Theoretical calculations revealed a large activation energy for such reaction, which thus cannot per se exclude the intervention of such radical species. Evidence for the likely operation of two concurrent mechanisms, a radical and a preponderant ionic pathway, involving the conjugate base of the thiazolium salt, as the chemical model for 'active thiamine', and ArNO is presented for the formation of the products of the reaction.
- Ferreira, Luísa M.,Marques, M. Manuel B.,Glória, Paulo M.C.,Chaves, Humberto T.,Franco, Jo?o-Pedro P.,Mourato, Isabel,Antunes, José-Rafael T.,Rzepa, Henry S.,Lobo, Ana M.,Prabhakar, Sundaresan
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p. 7759 - 7770
(2008/12/21)
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- Photoanalogues of the initiation substrates of the RNA polymerase II, 5-azido-2-nitrobenzoyl derivatives of the ATP γ-amidophosphate: The possible photoinduced degradation of the functional group to an n-arylhydroxylamine
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Photoanlogues of the initiation substrates of the RNA polymerase II, N 3Ar-NH(CH2)nNHpppA where N3Ar is 5-azido-2-nitrobenzoyl group (n=2 or 4) were synthesized, allowing the preparation of photoreactive oligonu
- Popova,Mal'shakova,Alekseyev,Kudryashova,Shakirov,Savinkova,Drachkova,Godovikova
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p. 921 - 925
(2007/10/03)
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- An exceptionally stable Ti superoxide radical ion: A novel heterogeneous catalyst for the direct conversion of aromatic primary amines to nitro compounds
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A matrix-bound superoxide radical anion, generated by treating Ti(OR)4 (R =iPr, nBu) with H2O2, is a selective heterogeneous catalyst for the oxidation of anilines to the corresponding nitroarenes with 50 % aqueous H2O2 [Eq. (1)]. Yields of 82-98 % are obtained, even with anilines bearing electron-withdrawing substituents (R = NO2, COOH).
- Dewkar, Gajanan K.,Nikalje, Milind D.,Ali, Iliyas Sayyed,Paraskar, Abhimanyu S.,Jagtap,Sudalai
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p. 405 - 408
(2007/10/03)
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- Nucleophilic aromatic substitution of hydrogen in the reaction of tert- alkylamines with nitrosobenzenes - Synthesis and NMR study of N-(tert-alkyl)- ortho-nitrosoanilines
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The reaction of primary amines bearing tertiary alkyl groups (e.g. R- NH2; R = tBu, 1-adamantyl) with nitrosobenzenes has been found to proceed by oxidative nucleophilic aromatic substitution of hydrogen, thereby affording N-(tert-alkyl)ortho- and -para-nitrosoanilines. The replacement of hydrogen proceeds more rapidly than the replacement of ortho- or para-nitro or -bromo substituents. With p-nitronitrosobenzene, both ortho-hydrogen atoms are substituted to afford N,N'-di(tert-alkyl)-4-nitro-2-nitroso-1,3- phenylenediamines 8a,b. The addition of oxidizing agents (e.g. MnO2) increases the yield of products. 1H-, 13C-, 14N- and 15N-NMR studies have confirmed the structures of the compounds under investigation. In ortho- nitrosoanilines, the rotamer with the nitroso group syn to the amino group is favored.
- Lipilin, Dmitriy L.,Churakov, Aleksandr M.,Ioffe, Sema L.,Strelenko, Yuri A.,Tartakovsky, Vladimir A.
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- Reactions of 2-acylthiazolium salts with N-arylhydroxylamines
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2-Acylthiazolium salts, easily obtained by alkylation of the corresponding 2-acylthiazoles with methyl triflate, react with N- arylhydroxylamines to furnish the O-acyl derivatives of relevance in the induction of cancer by aromatic mines.
- Ferreira, Luisa M.,Lobo, Ana M.,Prabhakar, Sundaresan,Teixeira, Antonieta C.
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p. 3541 - 3552
(2007/10/03)
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- Oxidation of Primary Aromatic Amines, Catalyzed by Tungsten Compounds
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Treatment of o-nitroanilines and o-aminobenzoic acids with 30 percent hydrogen peroxide in the presence of Na2WO4 and H3PO4 results in selective formation of corresponding nitroso derivatives.In other cases, the products are azoxy compounds.Oxidation of anilines containing alkyl or alkoxy groups in the ortho and para positions with hydrogen peroxide in the presence of Na2WO4 and tetrabutylammonium bromide quantitatively yields corresponding nitrosobenzenes.The H2O2-Na2WO4-H3PO4 system in the presence of tetrabutylammonium bromide is proposed for preparation of nitroso derivatives from anilines containing electron-acceptor meta and para substituents.
- Mel'nikov, E. B.,Suboch, G. A.,Belyaev, E. Yu.
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p. 1640 - 1642
(2007/10/03)
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- Catalytic selective oxidation of amines with hydroperoxides over molecular sieves: Investigations into the reaction of alkylamines, arylamines, allylamines and benzylamines with H2O2 and TBHP over TS-1 and CrS-2 as the new catalyst
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The liquid phase oxidation of various substituted amines with dil H2O2 and tert-butyl hydroxyperoxide (TBHP) has been investigated over titanium and chromium silicates respectively. While TS-1/H2O2 combination exhibits a remarkable activity and selectivity in the oxidation of arylamines to produce the symmetrical azoxybenzenes, CrS-2 catalyzes the selective oxidation of various substituted amines to the corresponding nitro compounds by oxidation with 70% TBHP. The nature of the reactive intermediates during the oxidation of anilines to nitrobenzenes has been established using cyclic voltammetry experiments. Further, amines possessing α C-H bonds are selectively oxidized to either oximes or the carbonyl compounds on reaction with H2O2 catalyzed by TS-1.
- Suresh,Joseph,Jayachandran,Pol,Vinod,Sudalai,Sonawane,Ravindranathan
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p. 11305 - 11318
(2007/10/02)
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- Competitive Base-Induced α-Elimination and Methanolysis of N-Aryl-O-pivaloylhydroxylamines
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The N-aryl-O-pivaloylhydroxylamines 1a-c are quite stable in MeOH under neutral conditions, but under mildly basic conditions (0.05 M Et2NH or Et3N) they undergo rapid decomposition (t1/2 = ca. 3-5 h at 25 deg C) by two competitive processes: apparent α-elimination to generate the nitrenes 2a-c and pivalic acid and basic ester methanolysis to generate the hydroxylamines 3a-c and methyl pivalate.The nitrenes decompose into the corresponding anilines 5 and azobenzenes 7, while the hydroxylamines undergo nitrene-mediated oxidation into the corresponding azoxybenzenes 6.The mechanism of this latter process was probed by addition of excess hydroxylamine, and a mechanism for the oxidation consistent with available data (Scheme II) is proposed.It was also found that the nitrosobenzenes 8 undergo nucleophilic attack by conjugate bases 4a-c of the title compounds to produce one of the two possible isomeric nonsymmetrical azoxybenzenes.
- Novak, Michael,Martin, Kristy A.,Heinrich, Julie L.,Peet, Kristine M.,Mohler, Linda K.
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p. 3023 - 3028
(2007/10/02)
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- Hydrolysis and Fe2+-induced Reduction of N-Aryl -O-pivaloylhydroxylamines: Aqueous Solution Chemistry of Model Carcinogens.
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The N-aryl-O-pivaloylhydroxylamines, 1a-d, which serve as models for the carcinogenic metabolites of aromatic amines, decompose in aqueous media by heterolysis of the N-O bond.Substituent effects on rates of reaction and products of the decomposition of 1a-c are entirely consistent with the intermediacy of a singlet nitrenium ion.The least reactive compound in the series N-(4-nitrophenyl)-O-pivaloylhydroxylamine (1d) yields 4-nitroaniline (2d) as its major decomposition product.This material may be formed through H radical abstraction by a triplet ion, but a nitrene reaction appears to be more likely.In the presence of Fe2+ 1a-d undergo rapid reduction to the corresponding anilines 2a-d.This reaction requires complexation of the ester with Fe2+ and proceeds with heterolysis of the N-O bond since nearly quantitative yields of pivalic acid are isolated.The radical cations 25a-d appear to be the most likely precursors to the reduction products.
- Novak, Michael,Lagerman, Robert K.
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p. 4762 - 4769
(2007/10/02)
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- Photochemistry of 3- and 4-Nitrophenyl Azides: Detection and Characterization of Reactive Intermediates
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Irradiation of nitro-substituted aromatic azides initiates a complex series of chemical reactions that lead to different products depending on the details of the experiment.There is evidence that four reactive intermediates participate in product-determining reactions.These are the singlet nitrene, the triplet nitrene, the triplet azide, and the ring-expanded dehydroazepine.The chemical and physical properties of each of these species is modified by the nitro substituent.The reactivity of the singlet nitrene with nucleophilic amines is increased, the lifetime of the dehydroazepine is shortened, and the triplet nitrene becomes a powerful single-electron acceptor.Nitro-substituted aromatic azides are widely used in photolabeling experiments.The findings of this study suggest that they may be inappropriate choices as photolabeling agents in many circumstances.
- Liang, Tsuei-Yun,Schuster, Gary B.
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p. 7803 - 7810
(2007/10/02)
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- Photochemistry in a Heterogenous System: Chlorophyll-Sensitized Reduction of p-Dinitrobenzene by Hydrazobenzene
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The photoreduction of p-dinitrobenzene, sensitized by aqueous suspensions of chlorophyll a with other amphiphiles adsorbed onto polyethylene-tetradecane particles, differs in some respects from the photoreduction in solution.The reaction proceeds in two stages.The products of the first stage, N-(p-nitrophenyl)hydroxylamine and azobenzene, are separated into the aqueous and hydrocarbon particles phases, respectively.The nature of the second stage of reaction is uncertain, but observations are best explained by a reduction of N-(p-nitrophenyl)hydroxylamine to 4,4'-dinitrohydrazobenzene.The quantum yield of photoreduction to the hydroxylamine does not seem to correlate at all with the quantum yield of fluorescence of the sensitizing particles.This and the relative magnitudes of the yields suggest that the principal photochemical reaction is reduction of dinitrobenzene not by the excited singlet state of chlorophyll or by the triplet state formed directly by intersystem crossing but by high-energy ion pair states or perhaps triplets formed from them by decay.Absorption spectrometry in the heterogeneous system is complicated by superposition of the so-called sieve effect on the path-lenth enhancement effect of the highly scattering system.The role of the interface between the particle and aqueous phases on the course of the reaction is discussed.
- Seeley, G. R.,Haggy, G. A.
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p. 440 - 447
(2007/10/02)
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- 1,3-Dipolar Cycloadditions, 86. Aromatic Azoxy Compounds and Strained Cycloalkenes
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4,4'-Dicyano- and 4,4'-dinitroazoxybenzene as well as benzocinnoline N-oxide combine with (E)-cyclooctene or (1E,5Z)-1,5-cyclooctadiene to give bicyclic 1,2,3-oxadiazolidines which undergo in situ 1,3-dipolar cycloreversion with opening of both rings.Azomethine imines are formed which are connected by a hexamethylene chain with an aldehyde function.These new 1,3-dipoles add to a second molecule of the strained cycloalkene and furnish derivatives of cyclooctapyrazole as 1:2 adducts in high yields.A 1,4 H-shift of the intermediate azomethine imine competes at low concentration of the (E)-cyclooctene and produces an 8-hydrazino-7-octenal as a 1:1 product.
- Huisgen, Rolf,Gambra, Francisco Palacios
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p. 2242 - 2255
(2007/10/02)
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