- Shape-controlled synthesis and catalytic behavior of supported platinum nanoparticles
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A 5 wt% Pt/C catalyst with around 20 nm cubic platinum particles was prepared through a conventional preparation method (i.e., precursor impregnation, reduction, and calcination) by choosing to use hydrophobic solvent in the impregnation procedure. The pr
- Liu, Changkun,Zhou, Zhenhua,Wu, Zhihua,Fransson, Martin,Zhou, Bing
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- Reaction pathways and the role of solvent in the hydrogenation of chloronitrobenzenes
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Liquid phase hydrogenation of chloronitrobenzenes to corresponding chloroanilines over Pd on carbon (Pd/C) under mild reaction conditions was studied. On the basis of 1H, 13C NMR, GC-MS and HPLC analyses of reaction mixtures, the reaction pathways were evaluated. The reduction of substrates proceeds via the formation of chloronitrosobenzenes and N-(chlorophenyl)hydroxylamines and mainly results in the formation of the chloroanilines and aniline. Aniline is formed by hydrogenolysis of chlorine (dechlorination) in benzene ring. Other compounds (mono- and disubstituted azobenzenes and azoxybenzenes) were also detected by GS-MS and HPLC (3 mole %). The used solvent influences the reaction mixture composition and catalyst activity.
- Kratky, Vieroslav,Kralik, Milan,Kaszonyi, Alexander,Stolcova, Magdalena,Zalibera, Lubomir,Mecarova, Miroslava,Hronec, Milan
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- Factors determining the chemoselectivity of phosphorus-modified palladium catalysts in the hydrogenation of chloronitrobenzenes
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The precursor nature effect on the state of the Pd–P surface layer in palladium catalysts and on their properties in the liquid-phase hydrogenation of chloronitrobenzenes under mild conditions has been investigated. A general feature of the Pd–P-containing nanoparticles obtained from different precursors and white phosphorus at P/Pd = 0.3 (PdCl2 precursor) and 0.7 (Pd(acac)2 precursor) is that their surface contains palladium in phosphide form (BE(Pd3d5/2) = 336.2 eV and BE(Р2р) = 128.9 eV) and Pd(0) clusters (BE(Pd3d5/2) = 335.7 eV). Factors having an effect on the chemoselectivity of the palladium catalysts in chloronitrobenzenes hydrogenation are considered, including the formation of small palladium clusters responsible for hydrogenation under mild conditions.
- Skripov,Belykh,Sterenchuk,Akimov,Tauson,Schmidt
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- METHOD OF REDUCING AROMATIC NITRO COMPOUNDS
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A method for reducing a substrate selected from 2-methyl-5-nitropyridine and methyl 4-(2-fluoro-3-nitrobenzyl)piperazine-1-carboxylate is provided catalysed by a nitroreductase and a disproportionation agent.
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Paragraph 0332; 0342
(2022/02/26)
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- Selective Photoinduced Reduction of Nitroarenes to N-Arylhydroxylamines
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We report the selective photoinduced reduction of nitroarenes to N-arylhydroxylamines. The present methodology facilitates this transformation in the absence of catalyst or additives and uses only light and methylhydrazine. This noncatalytic photoinduced transformation proceeds with a broad scope, excellent functional-group tolerance, and high yields. The potential of this protocol reflects on the selective and straightforward conversion of two general antibiotics, azomycin and chloramphenicol, to the bioactive hydroxylamine species.
- Kallitsakis, Michael G.,Ioannou, Dimitris I.,Terzidis, Michael A.,Kostakis, George E.,Lykakis, Ioannis N.
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supporting information
p. 4339 - 4343
(2020/06/08)
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- Selective hydrogenation of nitroaromatics to: N -arylhydroxylamines in a micropacked bed reactor with passivated catalyst
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In this contribution, a protocol was established for the selective catalytic hydrogenation of nitroarenes to the corresponding N-arylhydroxylamines. The reduction of 1-(4-chlorophenyl)-3-((2-nitrobenzyl)oxy)-1H-pyrazole, an intermediate in the synthesis of the antifungal reagent pyraclostrobin that includes carbon-chlorine bonds, benzyl groups, carbon-carbon double bonds and other structures that are easily reduced, was chosen as the model reaction for catalyst evaluation and condition optimization. Extensive passivant evaluation showed that RANEY-nickel treated with ammonia/DMSO (1 : 10, v/v) afforded the optimal result, especially with a particle size of 400-500 mesh. To combine the modified catalyst with continuous-flow reaction technology, the reaction was conducted at room temperature, rendering the desired product with a conversion rate of 99.4% and a selectivity of 99.8%. The regeneration of catalytic activity was also studied, and an in-column strategy was developed by pumping the passivate liquid overnight. Finally, the generality of the method was explored, and 7 substrates were developed, most of which showed a good conversion rate and selectivity, indicating that the method has a certain degree of generality.
- Chen, Jian-Li,Cheng, Peng-Fei,Jiang, Zhi-Jiang,Su, Wei-Ke,Xu, Feng,Yu, Zhi-Qun
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p. 28585 - 28594
(2020/08/25)
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- A general and scalable synthesis of polysubstituted indoles
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A consecutive 2-step synthesis of N-unprotected polysubstituted indoles bearing an electron-withdrawing group at the C-3 position from readily available nitroarenes is reported. The protocol is based on the [3,3]-sigmatropic rearrangement of N-oxyenamines generated by the DABCO-catalyzed reaction of N-arylhydroxylamines and conjugated terminal alkynes, and delivers indoles endowed with a wide array of substitution patterns and topologies.
- Diana-Rivero, Raquel,García-Tellado, Fernando,Tejedor, David
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- Highly Selective and Solvent-Dependent Reduction of Nitrobenzene to N-Phenylhydroxylamine, Azoxybenzene, and Aniline Catalyzed by Phosphino-Modified Polymer Immobilized Ionic Liquid-Stabilized AuNPs
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Gold nanoparticles stabilized by phosphine-decorated polymer immobilized ionic liquids (AuNP@PPh2-PIILP) is an extremely efficient multiproduct selective catalyst for the sodium borohydride-mediated reduction of nitrobenzene giving N-phenylhydroxylamine, azoxybenzene, or aniline as the sole product under mild conditions and a very low catalyst loading. The use of a single nanoparticle-based catalyst for the partial and complete reduction of nitroarenes to afford three different products with exceptionally high selectivities is unprecedented. Under optimum conditions, thermodynamically unfavorable N-phenylhydroxylamine can be obtained as the sole product in near quantitative yield in water, whereas a change in reaction solvent to ethanol results in a dramatic switch in selectivity to afford azoxybenzene. The key to obtaining such a high selectivity for N-phenylhydroxylamine is the use of a nitrogen atmosphere at room temperature as reactions conducted under an inert atmosphere occur via the direct pathway and are essentially irreversible, while reactions in air afford significant amounts of azoxy-based products by virtue of competing condensation due to reversible formation of N-phenylhydroxylamine. Ultimately, aniline can also be obtained quantitatively and selectively by adjusting the reaction temperature and time accordingly. Introduction of PEG onto the polyionic liquid resulted in a dramatic improvement in catalyst efficiency such that N-phenylhydroxylamine could be obtained with a turnover number (TON) of 100000 (turnover frequency (TOF) of 73000 h-1, with >99% selectivity), azoxybenzene with a TON of 55000 (TOF of 37000 h-1 with 100% selectivity), and aniline with a TON of 500000 (TOF of 62500 h-1, with 100% selectivity). As the combination of ionic liquid and phosphine is required to achieve high activity and selectivity, further studies are currently underway to explore whether interfacial electronic effects influence adsorption and thereby selectivity and whether channeling of the substrate by the electrostatic potential around the AuNPs is responsible for the high activity. This is the first report of a AuNP-based system that can selectively reduce nitroarenes to either of two synthetically important intermediates as well as aniline and, in this regard, is an exciting discovery that will form the basis to develop a continuous flow process enabling facile scale-up.
- Doherty, Simon,Knight, Julian G.,Backhouse, Tom,Summers, Ryan J.,Abood, Einas,Simpson, William,Paget, William,Bourne, Richard A.,Chamberlain, Thomas W.,Stones, Rebecca,Lovelock, Kevin R. J.,Seymour, Jake M.,Isaacs, Mark A.,Hardacre, Christopher,Daly, Helen,Rees, Nicholas H.
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p. 4777 - 4791
(2019/05/17)
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- Regioselective installation of fluorosulfate (-OSO2F) functionality into aromatic C(sp2)-H bonds for the construction of: Para-amino-arylfluorosulfates
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The construction of para-amino-arylfluorosulfates was achieved through installation of fluorosulfate (-OSO2F) functionality into aromatic C(sp2)-H bonds by the reaction of N-arylhydroxylamine with sulfuryl fluoride (SO2Fs
- Fang, Wan-Yin,Zha, Gao-Feng,Zhao, Chuang,Qin, Hua-Li
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supporting information
p. 6273 - 6276
(2019/06/07)
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- Laccases for bio-bleaching
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Provided herein are isolated laccase enzymes and nucleic acids encoding them. Also provided are mediators for laccase reactions. Also provided herein are methods for using laccases to oxidize lignins and other phenolic and aromatic compounds, such as for bio-bleaching and decolorization of wood pulp under high temperature and pH conditions to facilitate a substantial reduction in use of bleaching chemicals, as well as for treatment of fibers.
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Page/Page column 26
(2016/06/28)
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- An asymmetric pericyclic cascade approach to 3-alkyl-3-aryloxindoles: Generality, applications and mechanistic investigations
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The reaction of L-serine derived N-arylnitrones with alkylarylketenes generates asymmetric 3-alkyl-3-aryloxindoles in good to excellent yields (up to 93%) and excellent enantioselectivity (up to 98% ee) via a pericyclic cascade process. The optimization, scope and applications of this transformation are reported, alongside further synthetic and computational investigations. The preparation of the enantiomer of a Roche anti-cancer agent (RO4999200) 1 (96% ee) in three steps demonstrates the potential utility of this methodology.
- Richmond, Edward,Ling, Kenneth B.,Duguet, Nicolas,Manton, Lois B.,elebi-?lcüm, Nihan,Lam, Yu-Hong,Alsancak, Sezen,Slawin, Alexandra M. Z.,Houk,Smith, Andrew D.
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supporting information
p. 1807 - 1817
(2015/02/19)
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- A study on the selective hydrogenation of nitroaromatics to N-arylhydroxylamines using a supported Pt nanoparticle catalyst
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A supported Pt nanoparticle-based catalyst was used in the chemoselective hydrogenation of nitroarenes to N-arylhydroxylamines (N-AHA). Optimization of NB hydrogenation conditions showed that substantially higher N-PHA yields can be obtained at low temperature. Especially, the influence of an increased hydrogen pressure on selectivity is remarkable. Maximum yields increase from 55% N-PHA at 4 bar H2 to 80% at 23 bar H2 in ethanol. Further optimization led to the use of small amounts of amine additive, TMEDA, with 50 bar H2 raising the maximum yield to 97% N-PHA. The decreased N-PHA hydrogenation rate at high H2 pressure and the presence of TMEDA allow for selective transformation of a range of other nitroarenes containing electron-withdrawing and -donating (reducible) functional groups to their N-AHAs in excellent (more than 90%) yields.
- Boymans, Evert H.,Witte,Vogt
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p. 176 - 183
(2015/02/19)
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- Rhodium(III)-catalyzed internal oxidative coupling of N-hydroxyanilides with alkenes via C-H activation
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Abstract Described herein is an efficient new method for ortho-olefination of anilides in the presence of AgSbF6 and NaOAc via rhodium(III)-catalyzed internal oxidative C-H bond activation based on hydroxyl as directing and oxidative group. A range of alkenes and functional groups on acetanilides is supported and a possible mechanism is proposed according to the experimental results.
- Wen, Jing,Wu, An,Chen, Pei,Zhu, Jin
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supporting information
p. 5282 - 5286
(2015/08/26)
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- Solid supported platinum(0) nanoparticles catalyzed chemo-selective reduction of nitroarenes to N-arylhydroxylamines
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Solid supported platinum(0) (SS-Pt) nanoparticles were developed as a heterogeneous catalyst following a reduction/deposition method and characterized by SEM, TEM, EDX and XRD analysis. The SS-Pt catalyst was applied in the chemo-selective reduction of nitroarenes to N-arylhydroxylamines using hydrazine hydrate as a hydrogen source. A wide variety of reducible functional groups such as halides, carboxylic acids, esters, amides, nitriles, keto, alkenes, alkynes and N-benzyl were well tolerated under the reaction conditions. This process was further successfully employed in 10 g scale reactions. N-Arylhydroxylamines were further applied for catalyst free synthesis of azoxybenzenes. Moreover, use of PEG-400 as cheap reaction medium, additive free methodology and the recyclability of SS-Pt catalyst up to ten times without significant loss of catalytic activity evidently follow the principles of green chemistry.
- Shil, Arun K.,Das, Pralay
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supporting information
p. 3421 - 3428
(2013/12/04)
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- Selective reduction of nitroarenes to N-arylhydroxylamines by use of Zn in a CO2-H2O system, promoted by ultrasound
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The promoting effect of ultrasound on the selective reduction of nitroarenes to N-arylhydroxylamines by use of Zn in an environmentally benign CO2-H2O system has been demonstrated. The yield of N-phenylhydroxylamine reaches 95% when the reaction is carried out with a Zn-to-nitrobenzene molar ratio of 2.2 under ultrasound (40 kHz) at 25 °C and normal pressure of CO2 for 60 min. Application of ultrasound to the reaction has the advantages of higher yield of N-arylhydroxylamines, shorter reaction time, and consumption of less Zn. Springer Science+Business Media B.V. 2012.
- Liu, Shijuan,Wang, Yanhua,Yang, Xun,Jiang, Jingyang
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p. 2471 - 2478
(2013/02/25)
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- PROCESS FOR PREPARING SUBSTITUTED N-PHENYLHYDROXYLAMINES
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The present invention relates to a process for the preparation of 2-[[[1-(4-chlorophenyl)-1H-pyrazol-3-yl]oxy]methyl] phenyl]-hydroxylamine from the correspondingly substituted nitrobenzene compound.
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Page/Page column 10
(2012/09/22)
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- Effect of substituents on the rate of oxidation of anilines with peroxomonosulfate monoanion (HOOSO3-) in aqueous acetonitrile: A mechanistic study
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Mechanistic studies on the oxidation of 18 meta-, para-, and ortho-substituted anilines (Ans) by HOOSO3- in aqueous acetonitrile medium have been performed. The reaction can be characterized by the experimental rate equation, -d[HSO5-]/dt = k[An][HSO5-] The addition of p-toluenesulfonic acid (TsOH) retards the reaction. The increase in the reactivity of anilines as the medium is made more aqueous is interpreted. The reaction is enhanced by electron-donating groups on the amine in the series consistent with the rate-limiting nucleophilic attack of the amine on the persulfate oxygen. The proposed mechanism involves the conversion of phenylhydroxylamine to nitrosobenzene in a fast step. The ESR study reveals the absence of free radicals in the reaction. Various attempts have been made to analyze the experimental rate constants in terms of LFER plots. Improved correlations are obtained with σ- values and the σ- form of the Yukawa-Tsuno equation.
- Meenakshisundaram, Subbiah,Selvaraju,Made Gowda,Rangappa, Kanchugarakoppal S.
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p. 649 - 657
(2007/10/03)
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- Reactions of nitrosoarenes containing electron-withdrawing substituents with coordinated CO. Synthesis and structure of complexes Pd2(OAc) 2(p-ClC6H4N[p-ClC6H 3NO])2 and Pd2(OAc)2(o-ClC 6H4N[o-ClC6H3NO])2
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The reaction of tetranuclear Pd4(μ-COOCH3) 4(μ-CO)4 cluster (1a) with p- and o- chloronitrosobenzenes was found to give dinuclear nitrosoamide complexes, Pd2(OAc)2(p-ClC6H4N[p-ClC 6H3NO])2 (4) and Pd2(OAc) 2(o-ClC6H4N[o-ClC6H 3NO])2 (5), respectively. The formation of complexes 4 and 5 is accompanied by evolution of CO2, resulting from oxidation of CO coordinated in cluster 1. Complexes 4 and 5 were characterized by elemental analysis and IR and 1H NMR spectroscopy; their structures were studied by EXAFS. The reactions of dinuclear complex 4 with molecular hydrogen and CO were studied. The major products of reduction of 4 with hydrogen include metallic palladium, acetic acid, cyclohexanone, and molecular nitrogen. Treatment of complex 4 with CO under mild conditions (1 atm, 20°C) affords p-chlorophenyl isocyanate.
- Orlova,Stromnova,Kazyul'kin,Boganova,Kochubey,Novgorodov
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p. 819 - 824
(2007/10/03)
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- Mechanism and reactivity in perborate oxidation of anilines in acetic acid
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Perborate but not percarbonate in acetic acid generates peracetic acid on standing and the peracetic acid oxidation of anilines is fast. The oxidation with a fresh solution of perborate in acetic acid is smooth and second order but the specific oxidation rate increases with increasing [perborate]0 or [boric acid]. Perborate on dissolution affords hydrogen peroxide and a borate; the latter assists the former in the oxidation. The oxidation rates of anilines under identical conditions do not conform to any of the linear free energy relationships but the reaction rates of molecular anilines do. Perborate oxidation proceeds via two reaction paths but the overall oxidation rates of molecular anilines conform to structure reactivity relationships; the transition states do not differ significantly. Analysis of the oxidation rates of perborate and percarbonate reveals that while perborate oxidation is faster than percarbonate it is at least as selective as the latter.
- Karunakaran, Chockalingam,Kamalam, Ramasamy
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p. 2011 - 2018
(2007/10/03)
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- Reduction of nitroarenes to N-arylhydroxylamines with KBH4/BiCl3 system
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Aromatic nitro compounds could be selectively and rapidly reduced to the corresponding N-arylhydroxylamines in good yields with KBH4/BiCl3 system under mild conditions.
- Ren, Ping-Da,Pan, Xin-Wei,Jin, Qi-Hui,Yao, Zi-Peng
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p. 3497 - 3503
(2007/10/03)
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- A facile synthesis of N-aryl-N-hydroxyformamides from N-arylhydroxylamines
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Several N-arylhydroxylamines (2) have been formylated for the first time with acetic formic anhydride to yield N-hydroxyformanilides (3) in better yields than hitherto reported.
- Ayyangar, N. R.,Brahme, K. C.,Shingare, M. S.,Srinivasan, K. V.
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p. 961 - 963
(2007/10/02)
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- Proximity Effects in Diaryl Derivatives. Part 7. Mechanism of Base-catalysed Rearrangement of 2-(Hydroxyamino)aryl Phenyl Sulphones to 2-Hydroxy-2'-(phenylsulphonyl)azoxybenzenes
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Base-catalysed rearrangement of a 2-(hydroxyamino)aryl phenyl sulphone (1b) to the 2-hydroxy-2'-(phenylsulphonyl)azoxybenzene (4b) was shown by isolation and kinetic studies to be a rapid reaction requiring oxygen; in the absence of oxygen the sulphur-free azoxybenzene (3; R=Cl) was the only product isolated from the reaction of (1c).A mechanism for the formation of 2-hydroxyazoxybenzenes (4) is proposed (Scheme 2) involving dimerization of a nitrosoaryl radical anion (9) to the dianion of an NN-diol (10), and displacement of a phenylsulphonyl group by intramolecular transfer of oxygen from a nitrogen atom.A similar study of the base-catalysed reactions of a 2-(hydroxyamino)aryl phenyl sulphide (12) in the presence of oxygen showed that with a poorer leaving group the bis(phenylthio)azoxybenzene (11; R=SPh) is formed.An improved procedure for the preparation of N-arylhydroxylamines from nitrobenzenes is described.
- Cummings, Robert J.,Grundon, Michael F.,Knipe, Anthony C.,Wasfi, Adil S.
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p. 105 - 108
(2007/10/02)
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- Kinetics and Mechanism of Polarographic Reduction of Aromatic Nitro Compounds in Aqueous Alcoholic Medium
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Polarographic reduction of nitrobenzene, ortho-, meta- and para- chloronitrobenzenes, nitrotoluenes, nitrophenols and nitrobenzaldehydes has been studied in 25percent (v/v) aqueous ethanolic solutions, using Britton-Robinson (BR) buffer of varying pH values.KCl (0.1 M) has been used as the supporting electrolyte and Triton X-100 (0.001percent) as the maxima suppressor.The potential-dependent rate constant, kf,h has been calculated by Koutecky's method at different pH values and the values of kinetic parameters (αna and kf,h) have been calculated from logkf,h versus Ed.e. plots which are linear thereby suggesting that only a single rate-determining step is involved in the electrode process of each depolarizer.Based on the values of kinetic parameter, αna and the variation of E1/2 with pH, the stoichiometry of the rate-determining step has been established.This has led to the postulation of a tentative mechanism for the polarographic reduction of each depolarizer.Besides, the effect of the nature and position of various substituents, viz.Cl, CH3, OH and CHO on the kinetics of the polarographic reduction of NO2 group has been investigated.
- Ratan, Ram,Rani, Rama,Singh, Mukhtar
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p. 664 - 670
(2007/10/02)
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- Novel Reactions: Part I - Facile Synthesis of Substituted ortho-Chloranilines from Nitrobenzene Derivatives
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N-Substituted benzo and acetohydroxamic acids (5), prepared from N-arylhydroxylamines and benzoyl or acetyl chloride, react readily with thionyl chloride at low temperature to give ortho-chloroanilide derivatives (6) in good yield.The latter (6) on hydrolysis give ortho-chloroanilines (10).Since the N-arylhydroxylamines are obtained from nitroarenes by partial reduction, the overall reaction amounts to the preparation of 10 from nitroarenes.
- Ayyangar, N. R.,Kalkote, U. R.,Nikrad, P. V.
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p. 872 - 877
(2007/10/02)
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- Polarographic Behaviour of Some ortho-Substituted Nitrobenzenes: Evaluation of Polarographic ortho-Shift
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The polarographic characteristics of thirteen ortho-substituted nitrobenzenes have been studied at 35 deg C +/- 0.1 deg C in a well-buffered medium of 50percent (v/v) aqueous ethanol, having pH 5.8.Reduction process for all the compounds is found to be ir
- Ganapathy, K,Ramanujam, M
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p. 1087 - 1089
(2007/10/02)
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- Kinetics and Mechanism of the Bamberger Rearrangement. Part 4. Rearrangement of Sterically Hindered Phenylhydroxylamines to 4-Aminophenols in Aqueous Sulphuric Acid Solution
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The rates of the Bamberger rearrangement of sterically hindered phenylhydroxylamines have been determined in aqueous sulphuric acid solution and the substituent effects (in particular, the steric effects) are discussed.The rate constants for phenylhydroxylamines with 2-substituents (Me, Cl, I) satisfied the Taft equation: log krel = ρ*?* - δES with ρ*-1.93 and δ-1.16.The result shows that steric hindrance of the substituents, in addition to the electron-donating effect, has an accelerating effect on the rates of the Bamberger rearrangement.The rate constants for 3-substituted 2-methylphenylhydroxylamines were generally greater than those for 5-substituted 2-methylphenylhydroxylamines.The difference was attributed to the 'buttressing effect' of neighbouring 3-substituents.This is the first example of steric acceleration of the Bamberger rearrangement.
- Sone, Takaaki,Hamamoto, Kazuhiro,Seiji, Yoshiyuki,Shinkai, Seiji,Manabe, Osamu
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p. 1596 - 1598
(2007/10/02)
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