- Photochemistry of p-Nitroacetophenone in 2-Propanol
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Upon irradiation in 2-propanol, p-nitroacetophenone 1 was reduced via the triplet state to p-hydroxyammoacetophenone 5 which was further reduced top-aminoacetophenone 2 and 4,4′-diacetylazobenzene 4. Similar irradiation of 5 also gave 2 and 4, and its oxidation by oxygen gave 4,4′-diacetylazoxybenzene 3. Photolysis of monomeric p-nitrosoacetophenone 6 afforded acetophenone and 3 that were not produced during the irradiation of 1 Possible photoreaction pathways were discussed on the basis of published mechanisms.
- Lin, Yuh-Nong,Jeng, Guang-Yan,Chan, Tung-Tan,Yen, Giann-Feng,Wong, Yih-Gang
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Read Online
- Differences in the selective reduction mechanism of 4-nitroacetophenone catalysed by rutile- And anatase-supported ruthenium catalysts
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Ru/TiO2 catalysts exhibit excellent catalytic performance for selective reduction of 4-nitroacetophenone to 4-aminoacetophenone at normal temperature and atmospheric hydrogen pressure. Moreover, 99.9% selectivity to 4-aminoacetophenone can be obtained over 2.7 wt% Ru/TiO2(anatase) catalyst even in a relatively wide temperature (55-115 °C) and time (1-12 h) range. Its excellent catalytic performance is derived from the activation of H2 on the Ru nanoparticles at atmospheric pressure and the strong interaction of nitro groups with the support surface. Additionally, Ru nanoparticles supported on different crystalline TiO2 phases (anatase and rutile) result in different reaction pathways for 4-nitroacetophenone. Since the Ti-Ti distance on the rutile surface is smaller than that on the anatase surface, the hydroxylamine species adsorbed on the Ti atoms of rutile are more susceptible to the coupling reaction. Therefore, Ru/TiO2(rutile) causes a series of intermediates to accumulate during the conversion process, while Ru/TiO2(anatase) allows the highly selective conversion of 4-nitroacetophenone to 4-aminophenone. In addition, Ru/TiO2(anatase) can achieve chemoselective reduction of nitroaromatics to the corresponding anilines in the presence of -CN, -CHO, and -COOH, especially nitroaromatics containing CC and CC, indicating the excellent applicability.
- Gu, Xianmo,Pei, Linjuan,Wang, Jie,Zhang, Jin,Zheng, Zhanfeng,Zhu, Pengqi
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Read Online
- Polystyrene stabilized iridium nanoparticles catalyzed chemo- and regio-selective semi-hydrogenation of nitroarenes to N-arylhydroxylamines
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Polystyrene stabilized Iridium (Ir@PS) nanoparticles (NPs) as a heterogeneous catalyst have been developed and characterized by IR, UV–Vis, SEM, TEM, EDX and XRD studies. The prepared Ir@PS catalyst showed excellent reactivity for chemo- and regio-selective controlled-hydrogenation of functionalized nitroarenes to corresponding N-arylhydroxylamine using hydrazine hydrate as reducing source and environmentally benign polyethylene glycol (PEG-400) as green solvent. The present methodology was applied for vast substrate scope and found to be compatible with wide range of reducible functional groups. The reaction performed at 85 °C or ambient temperature and completed within 5–80 minutes. The catalyst can easily be filtered out from reaction mixture and reusable.
- Bhattacherjee, Dhananjay,Das, Pralay,Kumar, Ajay,Shaifali,Zyryanov, Grigory V.
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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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- Catalyst-Free N-Deoxygenation by Photoexcitation of Hantzsch Ester
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A mild and operationally simple protocol for the deoxygenation of a variety of heteroaryl N-oxides and nitroarenes has been developed. A mixture of substrate and Hantzsch ester is proposed to result in an electron donor-acceptor complex, which upon blue-light irradiation undergoes photoinduced electron transfer between the two reactants to afford the products. N-oxide deoxygenation is demonstrated with 22 examples of functionally diverse substrates, and the chemoselective reduction of nitroarenes to the corresponding hydroxylamines is also shown.
- Cardinale, Luana,Jacobi Von Wangelin, Axel,Konev, Mikhail O.
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supporting information
(2020/02/15)
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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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- Synthesis of N-aryl and N-heteroaryl hydroxylamines via partial reduction of nitroarenes with soluble nanoparticle catalysts
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Polystyrene-supported ruthenium nanoparticles enable the selective hydrazine-mediated reduction of nitroarenes to hydroxylamine products in high yield and selectivity. Key to obtaining the hydroxylamine product in good yield was the use of organic solvents capable of solubilizing the polystyrene-supported nanoparticle catalyst. N-aryl and N-heteroaryl hydroxylamines are generated under exceptionally mild conditions and in the presence of a various easily reduced functional groups.
- Tyler, Jefferson H.,Nazari, S. Hadi,Patterson, Robert H.,Udumula, Venkatareddy,Smith, Stacey J.,Michaelis, David J.
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supporting information
p. 82 - 86
(2016/12/23)
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- TRIFLUOROMETHOXYLATION OF ARENES VIA INTRAMOLECULAR TRIFLUOROMETHOXY GROUP MIGRATION
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The present invention provides a process of producing a trifluoromethoxylated aryl or trifluoromethoxylated heteroaryl having the structure: (I), wherein A is an aryl or heteroaryl, each with or without subsutitution; and R1 is -H, -(alkyl), -(alkenyl), -(alkynyl), -(aryl), -(heteroaryl), - (alkylaryl), - (alkylheteroaryl), -NH-(alkyl), -N(alkyl)2, -NH-(alkenyl), -NH-(alkynyl) -NH-(aryl), -NH-(heteroaryl), -O-(alkyl), -O-(alkenyl), -O-(alkynyl), -O-(aryl), -O-(heteroaryl), -S-(alkyl), -S- (alkenyl), -S-(alkynyl), -S-(aryl), or -S-(heteroaryl), comprising: (a) reacting a compound having the structure: (II), with a trifluoromethylating agent in the presence of a base in a first suitable solvent under conditions to produce a compound having the structure: (III); and (b) maintaining the compound produced in step (a) in a second suitable solvent under conditions sufficient to produce the trifluoromethoxylated aryl or trifluormethoxylated heteroaryl having the structure: (I).
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Page/Page column 57
(2016/05/02)
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- Mechanistic studies on intramolecular C-H trifluoromethoxylation of (hetero)arenes via OCF3-migration
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The one-pot two-step intramolecular aryl and heteroaryl C-H trifluoromethoxylation recently reported by our group has provided a general, scalable, and operationally simple approach to access a wide range of unprecedented and valuable OCF3-containing building blocks. Herein we describe our investigations to elucidate its reaction mechanism. Experimental data indicate that the O-trifluoromethylation of N-(hetero)aryl-N-hydroxylamine derivatives is a radical process, whereas the OCF3-migration step proceeds via a heterolytic cleavage of the N-OCF3 bond followed by rapid recombination of a short-lived ion pair. Computational studies further support the proposed ion pair reaction pathway for the OCF3-migration process. We hope that the current study would provide useful insights for the development of new transformations using versatile N-(hetero)aryl-N-hydroxylamine synthons.
- Lee, Katarzyna N.,Lei, Zhen,Morales-Rivera, Cristian A.,Liu, Peng,Ngai, Ming-Yu
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supporting information
p. 5599 - 5605
(2016/07/06)
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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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- Trifluoromethoxylation of arenes: Synthesis of ortho- Trifluoromethoxylated aniline derivatives by OCF3 migration
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Aryl trifluoromethoxylation by a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxylamine derivatives and intramolecular OCF3 migration is presented. This protocol allows easy access to a wide range of synthetically useful ortho-OCF3 aniline derivatives. In addition, it utilizes bench-stable reagents, is operationally simple, shows high functional-group tolerance, and is amenable to gram-scale as well as one-pot synthesis.Areaction mechanism of a heterolytic cleavage of the N-OCF3 bond followed by recombination of the resulting nitrenium ion and trifluoromethoxide is proposed for the OCF3-migration reaction.
- Hojczyk, Katarzyna N.,Feng, Pengju,Zhan, Chengbo,Ngai, Ming-Yu
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supporting information
p. 14559 - 14563
(2015/01/09)
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- Highly selective and controllable synthesis of arylhydroxylamines by the reduction of nitroarenes with an electron-withdrawing group using a new nitroreductase BaNTR1
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A new bacterial nitroreductase has been identified and used as a biocatalyst for the controllable reduction of a variety of nitroarenes with an electron-withdrawing group to the corresponding N-arylhydroxylamines under mild reaction conditions with excellent selectivity (>99%). This method therefore represents a green and efficient method for the synthesis of arylhydroxylamines.
- Nguyen-Tran, Hieu-Huy,Zheng, Gao-Wei,Qian, Xu-Hong,Xu, Jian-He
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supporting information
p. 2861 - 2864
(2014/03/21)
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- Synthesis and antibacterial properties of new phenothiazinyl-and phenyl-nitrones
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The synthesis of new phenothiazinyl-and phenyl-nitrones under classical versus microwave heating conditions is described. Better yields were obtained under microwave irradiation in the condensation reactions of phenothiazyl-carbaldehyde with hydro-xylamine derivatives. The structures of the new phenothiazinyl-nitrones were assigned on the basis of MS, FT-IR and NMR spectra. The new nitrones and some known phenylnitrones were screened for their antibacterial and antifungal activity against several Candida species, Gram negative bacteria, such as E. coli, Citrobacter spp, Morganella spp, Pseudomonas aeruginosa, Klebsiella pneumoniae (±ESBL), Proteus spp, Acinetobacter spp and the Gram positive bacterium Staphylococcus aureus, with moderate results.
- Petkes, Hermina Iulia,Gál, Emese,Gaina, Luiza,Sabou, Mihaela,Majdik, Cornelia,Silaghi-Dumitrescu, Lumini?a
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p. 1050 - 1056
(2014/12/11)
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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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- Carbon supported Pt colloid as effective catalyst for selective hydrogenation of nitroarenes to arylhydroxylamines
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The Pt colloid supported on carbon is an active and selective catalyst for the partial hydrogenation of nitroaromatics with electron-withdrawing substituents to the corresponding N-arylhydroxylamine, indicating an additive-free green catalytic approach fo
- Rong, Zeming,Du, Wenqiang,Wang, Yue,Lu, Lianhai
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supporting information; experimental part
p. 1559 - 1561
(2010/06/12)
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- Solvent hydrogen bonding and structural influences on the CrVI oxidation of anilines in aqueous acetic acid medium
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The oxidation of meta- and para-substituted anilines by CrVI oxidant, imidazolium fluorochromate (IFC), in aqueous acetic acid mixtures of varying compositions in the presence of p-toluenesulfonic acid (PTS) is first order in IFC and PTS. Michaelis-Menten type kinetics is observed with all of the anilines. The IFC oxidation of 15 meta- and para-substituted anilines at 299-322 K complies with the isokinetic relationship but not to any of the linear free energy relationships. The isokinetic temperature lies within the experimental range. The rate data failed to correlate with macroscopic solvent parameters such as relative permittivity, εr, and ionizing power, Y, correlation of rate data with Kamlet-Taft solvatochromic parameters (hydrogen bond donor acidity, α, hydrogen bond acceptor basicity, β, and dipolarity/polarizability, π*) is linear which suggests that the specific solute-solvent interactions play a dominating role in governing the reactivity.
- Bhuvaneshwari,Elango
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experimental part
p. 242 - 249
(2010/04/26)
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- The selective reduction of nitroarenes to N-arylhydroxylamines using Zn in a CO2/H2O system
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Nitroarenes are reduced to the corresponding N-arylhydroxylamines with high selectivity using Zn dust in a CO2/H2O system under mild conditions. The yield of N-phenylhydroxylamine from nitrobenzene is 88% when the reaction is carried out at 25 °C for 1.5 hours with a Zn to nitrobenzene molar ratio equal to 3 under 0.1 MPa CO2. Other nitroarenes, which contain reducible functionality other than a nitro group, are also reduced to the corresponding N-arylhydroxylamines with yield from 88% to 99%. The process fully removes the need to use NH4Cl and is environmentally benign. The Royal Society of Chemistry 2009.
- Liu, Shijuan,Wang, Yanhua,Jiang, Jingyang,Jin, Zilin
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experimental part
p. 1397 - 1400
(2010/05/17)
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- Effect of solvent on the rate of oxidation of substituted anilines with nicotinium dichromate in aqueous-acetic acid media
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Mechanistic studies on the oxidation of 15 para- and meta-substituted anilines by nicotinium dichromate in water-acetic acid medium of varying mole fractions have been performed. The reaction can be characterized by the experimental rate equation, -d[oxidizing agent]/dt = Kk [substrate] [HCrO 4-]/(1 + K [substrate]) The addition of p-toluenesulfonic acid enhances the reaction. The oxidation substituted anilines at 299-322 K complies with the isokinetic relationship but not to any of the linear free energy relationships, the isokinetic temperature lies within the experimental range. Correlation of rate data with Kamlet-Taft solvatochromic parameters (α, β, π*) suggests that the specific solute-solvent interactions play a major role in governing the reactivity.
- Bhuvaneshwari,Elango
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p. 999 - 1005
(2007/10/03)
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- Ultrasound-promoted highly chemoselective reduction of aromatic nitro compounds to the corresponding N-arylhydroxylamines using zinc and HCOONH 4 in CH3CN
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N-Arylhydroxylamines were prepared in high yields through chemoselective reduction of the corresponding aromatic nitro compounds under ultrasound (59 kHz) at room temperature using a convenient Zn/HCOONH4/CH 3CN system. This method was highly efficient, environmentally benign, especially simple and practical. Copyright
- Shi, Qi Xun,Lu, Rong Wen,Jin, Kun,Zhang, Zhu Xia,Zhao, De Feng
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p. 226 - 227
(2007/10/03)
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- A novel strategy for the preparation of arylhydroxylamines: Chemoselective reduction of aromatic nitro compounds using bakers' yeast
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Using bakers' yeast as a biocatalyst, the chemoselective reduction of aromatic nitro compounds bearing electron-withdrawing groups gave the corresponding hydroxylamines with good to excellent conversion under mild conditions.
- Li, Feng,Cui, Jingnan,Qian, Xuhong,Zhang, Rong
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p. 2338 - 2339
(2007/10/03)
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- Formation of 4,4-dialkoxycyclohexa-2,5-dienone N-(Thiol-S-yl)imine during reaction of 4-alkoxynitrosobenzenes with Thiols in alcoholic solvents
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During the interaction of nitrosoarenes with glutathione in aqueous media, intermediate generation of a highly resonance-stabilized sulfenamide cation has been repeatedly suggested. Most intermediates and end products could be explained by reactions of this sulfenamide cation with different nucleophiles such as excess thiol, solvent water, and metabolically produced arylamine. The present paper presents evidence for adduct formation of the sulfenamide cation with solvent alcohol at neutral pH. Sulfenamide cations generated from 4-nitrosophenetole and 4-nitrosoanisole, respectively, are strongly suggested to form the metastable ketals 4-ethoxy-4-methoxycyclohexa- 2,5-dienone N-(glutathion-S-yl)imine and 4,4-dimethoxycyclohexa-2,5-dienone N-(glutathion-S-yl)imine, respectively, during reaction with solvent methanol. Reaction of the two sulfenamide cations in ethanol yielded 4,4- diethoxycyclohexa-2,5-dienone N-(glutathion-S-yl)imine and 4-ethoxy-4- methoxycyclohexa-2,5-dienone N-(glutathion-S-yl)-imine, respectively. Although the metastability of the ketals did not allow isolation of pure solid material, chromatographic and chemical behavior as well as tandem MS fragmentation substantiate a ketal structure of these intermediates. To confirm the proposed structure, new compounds, 2,6-dimethyl-4- nitrosophenetole, 2,6-dimethyl-4-nitrophenetole, 2,6-dimethyl-4-phenetidine, and N-(glutathion-S-yl)-N-hydroxy-4-aminoacetophenone, were synthesized and included in supportive experiments. In summary, the detection of ketals corroborates once more the occurrence of a sulfenamide cation which obviously not only reacts with Soft nucleophiles such as GSH but, to a limited extent, also reacts with hard nucleophiles. The toxicological significance of this result is discussed.
- Gallemann, Dieter,Buhrow, Ingrid
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p. 1423 - 1433
(2007/10/03)
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- Kinetics and Mechanism of Oxidation of para-Substituted Anilines by Peroxomonosulphate
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Kinetics of oxidation of several para-substituted anilines by peroxomonosulphate (PMS) in aqueous acetic acid medium have been investigated. The reaction follows a total second order, first order each in [PMS] and [substrate]. The reaction rate is retarted by both electron-releasing and withdrawing groups. Absence of free radical formation is confirmed. Activation energy and thermodynamic parameters have been computed. A probable mechanism has been proposed.
- Abdul Jameel,Maruthamuthu
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p. 368 - 370
(2007/10/03)
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- RUBREDOXIN MODEL COMPLEX (Et4N) AS A CATALYST IN THE REDUCTION OF AROMATIC NITRO COMPOUNDS TO HYDROXYLAMINES
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(Et4N), the analogue of oxidized rubredoxin active sites, can catalyze the reduction of aromatic nitro compounds to N-aryl hydroxylamines by o-xylene-α,α'-dithiol.
- Yanada, Kazuo,Nagano, Tetsuo,Hirobe, Masaaki
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p. 5113 - 5116
(2007/10/02)
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- Temperature-Dependent Acid Dissociation Constants (Ka, ΔHa, ΔSa) for a Series of Nitrogen-Substituted Hydroxamic Acids in Aqueous Solution
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The acid dissociation constants (Ka) of a series of eight substituted N-phenylacetohydroxamic acids, CH3C-(O)N(OH)C6H4X (X=H, 4-CH3, 4-Cl, 4-I, 3-I, 3-CN, 4-CN, 4-C(O)CH3), have been determined in aqueous solution (I=2.0) for a range of temperatures.The pKa data at 25 deg C exhibit a small variation with the substituent X in the direction expected according to their Hammett substituent constants (ρ ca. 0.1).These small variations in pKa values are due to compensating trends in ΔHa and ΔSa, which show significant variation with substituent.These results are discussed in terms of the substituent's influence on hydroxamate anion-solvent interactions and the relative influence on pKa of a substituted phenyl group attached to the C or N end of the hydroxamate moiety.
- Poth Brink, Christina,Crumbliss, Alvin L.
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p. 1171 - 1176
(2007/10/02)
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