- Electrochemically Tuned Oxidative [4+2] Annulation and Dioxygenation of Olefins with Hydroxamic Acids
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This work represents the first [4+2] annulation of hydroxamic acids with olefins for the synthesis of benzo[c][1,2]oxazines scaffold via anode-selective electrochemical oxidation. This protocol features mild conditions, is oxidant free, shows high regioselectivity and stereoselectivity, broad substrate scope of both alkenes and hydroxamic acids, and is compatible with terpenes, peptides, and steroids. Significantly, the dioxygenation of olefins employing hydroxamic acid is also successfully achieved by switching the anode material under the same reaction conditions. The study not only reveals a new reactivity of hydroxamic acids and its first application in electrosynthesis but also provides a successful example of anode material-tuned product selectivity.
- Wei, Bang-Yi,Xie, Dong-Tai,Lai, Sheng-Qiang,Jiang, Yu,Fu, Hong,Wei, Dian,Han, Bing
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supporting information
p. 3182 - 3188
(2020/12/11)
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- Redox-Neutral Selenium-Catalysed Isomerisation of para-Hydroxamic Acids into para-Aminophenols
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A selenium-catalysed para-hydroxylation of N-aryl-hydroxamic acids is reported. Mechanistically, the reaction comprises an N?O bond cleavage and consecutive selenium-induced [2,3]-rearrangement to deliver para-hydroxyaniline derivatives. The mechanism is studied through both 18O-crossover experiments as well as quantum chemical calculations. This redox-neutral transformation provides an unconventional synthetic approach to para-aminophenols.
- Chuang, Hsiang-Yu,Schupp, Manuel,Meyrelles, Ricardo,Maryasin, Boris,Maulide, Nuno
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supporting information
p. 13778 - 13782
(2021/03/31)
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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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- Tandem selective reduction of nitroarenes catalyzed by palladium nanoclusters
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We report a catalytic tandem reduction of nitroarenes by sodium borohydride (NaBH4) in aqueous solution under ambient conditions, which can selectively produce five categories of nitrogen-containing compounds: anilines, N-aryl hydroxylamines, azoxy-, azo- and hydrazo-compounds. The catalyst is in situ-generated ultrasmall palladium nanoclusters (Pd NCs, diameter of 1.3 ± 0.3 nm) from the reduction of Pd(OAc)2 by NaBH4. These highly active Pd NCs are stabilized by surface-coordinated nitroarenes, which inhibit the further growth and aggregation of Pd NCs. By controlling the concentration of Pd(OAc)2 (0.1-0.5 mol% of nitroarene) and NaBH4, the water/ethanol solvent ratio and the tandem reaction sequence, each of the five categories of N-containing compounds can be obtained with excellent yields (up to 98%) in less than 30 min at room temperature. This tunable catalytic tandem reaction works efficiently with a broad range of nitroarene substrates and offers a green and sustainable method for the rapid and large-scale production of valuable N-containing chemicals.
- Yan, Ziqiang,Xie, Xiaoyu,Song, Qun,Ma, Fulei,Sui, Xinyu,Huo, Ziyu,Ma, Mingming
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supporting information
p. 1301 - 1307
(2020/03/11)
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- Synthesis of sulpha drug based hydroxytriazene derivatives: Anti-diabetic, antioxidant, anti-inflammatory activity and their molecular docking studies
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Herein, we report synthesis, characterization, anti-diabetic, anti-inflammatory and anti-oxidant activities of hydroxytriazenes derived from sulpha drugs, namely sulphanilamide, sulphadiazine, sulphapyridine and sulphamethazine. Before biological screening of the compounds, theoretical prediction using PASS was done which indicates probable activities ranging from Pa (probable activity) values 65–98% for anti-inflammatory activity. As per the predication, experimental validation of some of the predicted activities particularly anti-diabetic, anti-inflammatory and anti-oxidant was done. Anti-diabetic activities have been screened using two methods namely α-amylase and α-glucosidase inhibition method and IC50 values were ranging from 66 to 260 and 148 to 401 μg/mL, while for standard drug acarbose the values were 12 μg/mL and 70 μg/mL, respectively. Docking studies have also been done for antidiabetic target pancreatic alpha amylase. The molecular docking studies in α-amylase enzyme reveal that the middle phenyl ring of all the compounds mainly occupies in the small hydrophobic pocket formed by the Ala198, Trp58, Leu162, Leu165 and Ile235 residues and sulphonamide moiety establish H-bond interaction by two water molecules. Further, anti-inflammatory activity has been evaluated using carrageenan induced paw-edema method and results indicate excellent anti-inflammatory activity by hydroxytriazenes (71 to 97%) and standard drug diclofenac 94% after 4 h of treatment. Moreover, antioxidant effect of the compounds was tested using DPPH and ABTS methods. All the compounds displayed good results (24–488 μg/mL) against ABTS radical and many compounds are more active than ascorbic acid (69 μg/mL) while all other compounds showed moderate activity against DPPH radical (292–774 μg/mL) and ascorbic acid (29 μg/mL). Thus, the studies reveal potential of sulfa drug based hydroxytriazenes as candidates for antidiabetic, anti-inflammatory and antioxidant activities which have been experimentally validated.
- Baroliya, Prabhat K.,Chauhan, R. S.,Dayma, Varsha,Dwivedi, Aparna,Goswami, A. K.,Sharma, Poonam,Tripathi, I. P.,Vanangamudi, Murugesan
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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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- 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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- Cobalt-Catalyzed Electrophilic Amination of Aryl- and Heteroarylzinc Pivalates with N-Hydroxylamine Benzoates
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Aryl- and heteroarylzinc pivalates can be aminated with O-benzoylhydroxylamines at 25 °C within 2–4 h in the presence of 2.5–5.0 % CoCl2?2 LiCl to furnish the corresponding tertiary arylated or heteroarylated amines in good yields. This electrophilic amination also provides access to diarylamines and aryl(heteroaryl)amines. A new tuberculosis drug candidate (Q203) was prepared in six steps and 56 % overall yield by using this cobalt-catalyzed amination as the key step.
- Chen, Yi-Hung,Gra?l, Simon,Knochel, Paul
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supporting information
p. 1108 - 1111
(2018/01/01)
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- Hydroxamic Acids as Chemoselective (ortho-Amino)arylation Reagents via Sigmatropic Rearrangement
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The use of readily available hydroxamic acids as reagents for the chemoselective (ortho-amino)arylation of amides is described. This reaction proceeds under metal-free, mild conditions, displays a very broad scope, and constitutes a direct approach for the metal-free attachment of aniline residues to carbonyl derivatives.
- Shaaban, Saad,Tona, Veronica,Peng, Bo,Maulide, Nuno
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supporting information
p. 10938 - 10941
(2017/08/30)
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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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- Synthesis, characterization, theoretical prediction of activities and evaluation of biological activities of some sulfacetamide based hydroxytriazenes
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Six new N [(4-aminophenyl)sulfonyl]acetamide based hydroxytriazenes have been synthesized and characterized using elemental analysis, IR, 1H NMR, 13C NMR and MASS spectral analysis. Further, their theoretical predictions for probable activities have been taken using PASS (Prediction of Activity Spectra for Substance). Although a number of activities have been predicted but specifically anti-inflammatory, antiradical, anti-diabetic activities have been experimentally validated which proves that theoretical predictions agree with the experimental results. The object of the Letter is to establish Computer Aided Drug Design (CADD) using our compounds.
- Agarwal, Shilpa,Baroliya, Prabhat K.,Bhargava, Amit,Tripathi,Goswami
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p. 2870 - 2873
(2016/06/06)
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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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- 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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- Interrupted fischer-indole intermediates via oxyarylation of alkenyl boronic acids
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The oxyarylation of alkenyl boronic acids with N-arylbenzhydroxamic acids has been achieved under both copper-mediated and copper-catalyzed conditions to provide access to interrupted Fischer-indole intermediates. This transformation is believed to proceed through a copper-promoted C-O bond forming event followed by a [3,3] rearrangement. The scope of the method is described and mechanistic experiments are discussed.
- Wang, Heng-Yen,Anderson, Laura L.
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supporting information
p. 3362 - 3365
(2013/07/26)
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- Photocatalytic cleavage of hydroxytriazenes: A solidstate synthesis of azo-dyes under sunlight irradiation
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Sunlight-induced decomposition of hydroxytriazenes, and green photochemical synthesis of azo-dyes is described. Three substituted hydroxytriazenes, viz: 3-hydroxy-3-(2-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (o-CFHT), 3-hydroxy-3-(3-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (m-CFHT), and 3-hydroxy-3-(4-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (p-CFHT) were co-crystallized with β-naphthol in equimolar ratio and exposed to sunlight for 9-10h. The reaction resulted in formation of azo-dyes which were identified by comparison with the products obtained by the conventional method (standard azodye), by use of HPLC. A probable mechanism has been suggested. This is first ecofriendly synthesis of azo-dyes using hydroxytriazenes. Springer Science+Business Media B.V. 2012.
- Baroliya, Prabhat Kumar,Mehta, Anita,Dashora, Rekha,Chauhan,Goswami
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p. 2149 - 2153
(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.
- -
-
Page/Page column 10
(2012/09/22)
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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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- Selective synthesis of N-aryl hydroxylamines by the hydrogenation of nitroaromatics using supported platinum catalysts
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Various substituted nitroaromatics were successfully hydrogenated to the corresponding N-aryl hydroxylamines in excellent yields (up to 99%) using supported platinum catalysts such as Pt/SiO2 under a hydrogen atmosphere (1 bar) at room temperature. The key to the fast and highly selective formation of hydroxylamines is the addition of small amounts of amines such as triethylamine and dimethyl sulfoxide; amines promote the conversion of nitroaromatics, while dimethyl sulfoxide inhibits further hydrogenation of hydroxylamines to anilines. The promotive effect depends on which type of amine and primary amine was most effective. The hydrogenation efficiently proceeded in common organic solvents, including isopropanol, diethyl ether, and acetone. This methodology should extend the application range of conventional solid catalysts to fine chemicals synthesis. The Royal Society of Chemistry 2009.
- Takenaka, Yasumasa,Kiyosu, Takahiro,Choi, Jun-Chul,Sakakura, Toshiyasu,Yasuda, Hiroyuki
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supporting information; experimental part
p. 1385 - 1390
(2010/05/18)
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- SDS/CH2(CN)EWG/H2O: An efficient and green system for the cleavage of nitrones and imines in water
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SDS/CH2(CN)EWG/H2O system (EWG= electron withdrawing group) reacted with nitrones and imines in water to produce addition-elimination products with excellent yields at room temperature.
- Sharma, Saikat Das,Gogoi, Pranjal,Konwar, Dilip
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p. 1672 - 1678
(2008/09/19)
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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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- 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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- Synthesis and characterization of thymidine adducts of arylamines
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The synthesis of adducts of arylamines with thymidine are reported.
- Kumar, N.V. Anil,Rangappa
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p. 259 - 264
(2007/10/03)
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- Synthesis of novel isoxazolidines via 1,3-dipolar cycloaddition of nitrones to olefins
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C-anthranyl-N-3-methylphenyl nitrone has been discovered as new 1,3-dipole to form N-arylisoxazolidines via 1,3-dipolar cycloaddition reaction with olefins. Synthesized novel isoxazolidines were characterized by 1H NMR, IR and C, H and N analys
- Vishu Kumar,Mantelingu,Basappa,Rangappa
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p. 161 - 164
(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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- Synthesis and characterization of adenosine adducts of arylamines
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The synthesis of adducts of arylamines with adenosine are reported.
- Anil Kumar,Mantelingu,Rangappa
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p. 463 - 467
(2007/10/03)
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- Synthesis, characterization, and conformational analysis of DNA adducts from methylated anilines present in tobacco smoke
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The ability of a series of aromatic amines present in tobacco smoke (2-, 3-, and 4-methylaniline, 2,3- and 2,4-dimethylaniline) to bind to DNA has been investigated by reacting N-(acyloxy)arylamines with dG, dG nucleotides, and DNA. The predominant products from reactions with dG and the nucleotides were characterized as N-(deoxyguanosin-8-yl)arylamines by spectroscopic and HPLC methods. HPLC and spectroscopic analyses of the modified DNA indicated the same adducts. Analyses of the 1H and 13C NMR spectra suggested that the adducts containing a methyl substituent ortho to the arylamine nitrogen had a higher percentage of syn conformers. This observation was supported by theoretical simulation studies that indicated substantial percentages of low energy syn conformers, increasing with the substitution pattern in the order para meta ortho ortho,para ortho,meta. The results demonstrate that, although single-ring arylamines are considered weak carcinogens, their electrophilic N-acetoxy derivatives, which are plausible metabolic intermediates, react with DNA to yield covalent adducts structurally identical to those derived from carcinogenic polyarylamines, such as 2- aminofluorene and 4-aminobiphenyl. Furthermore, the conformational perturbation induced in DNA by the formation of the monoarylamine-DNA adducts, especially those with an ortho substituent, may contribute to the biological activities of these compounds.
- Marques, M. Matilde,Mourato, Luisa L. G.,Santos, M. Amelia,Beland, Frederick A.
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-
- Synthesis, Properties, and Thermodynamic Ionization Constants of α-Phenylstyrylacrylohydroxamic Acids
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The synthesis and properties of eight new hydroxamic acids derived from α-phenylstyrylacrylic acids are described. These hydroxamic acids, which are crystalline compounds, were characterized by their ultraviolet, infrared, and NMR spectra. The purity was checked by HPLC and HPTLC. The nonaqueous titrations and alkaline hydrolysis are reported. Thermodynamic ionization constants at (25 and 35 +/- 0.1) deg C are determined. Preliminary studies show that these acids form a chloroform-extractable violet complex with vanadium(V) in 6 M hydrochloric acid solutions.
- Patel, Kalpesh R.,Menon, Sobhana K.,Agrawal, Yadvendra K.
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p. 423 - 425
(2007/10/03)
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- Electrophilic intermediate in the reaction of glutathione and nitrosoarenes
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A kinetic study is reported of the reaction of glutathione (γ-L-glutamyl-L-cysteinylglycine, GSH) with nine substituted nitrosobenzenes (3,4-Me2 4-Me, 3,5-Me2, 3-Me, parent, 3-MeO, 4-Cl, 3-Cl, 3-NO2). Previous workers have shown that this reaction proceeds in parallel pathways, producing the appropriate N-arylhydroxylamine and GSSG or a sulfinanilide adduct ArNHS(O)G; a rapid equilibrium addition to form a common intermediate, a semimercaptal ArN(OH)SG, has also been observed. In the present study, equilibrium constants for the formation of this intermediate from ArNO and GSH have been measured by a kinetic method, and the kinetic behavior of the slower additional reactions of the semimercaptal have been examined in detail. For experiments carried out at constant pH and buffer concentration, the decay of ArN(OH)SG follows the rate law k2GSH[GSH] + k2(rearr). A comparison with product ratios previously reported shows that the bimolecular term with GSH represents the process forming ArNHOH and GSSG, while the unimolecular term represents the rearrangement to the sulfmanilide. The former process is found to be proportional to [OH-] for solutions near neutrality, is not buffer catalyzed, and has a ρ value of +1.4. This suggests a mechanism in which glutathione anion GS- reacts at the sulfur of the adduct displacing ArN-(OH) as a leaving group. The rearrangement reaction follows σ+ with a ρ+ value of -3.5 and has a rate law containing a pH-independent term and terms for catalysis by H+ and the acid component of the buffer. An 18O tracer study shows that the S=O oxygen in the sulfmanilide is derived from solvent, not the original N=O group. A mechanism is proposed with rate-limiting N-O cleavage, either uncatalyzed involving direct heterolysis with OH- as a leaving group or catalyzed by acids with H2O as the leaving group. The species produced is a cationic intermediate ArN+SG, a nitrenium ion stabilized by both the aryl ring and the directly attached sulfur atom. Aryl-stabilized nitrenium ions are commonly encountered in Bamberger-like rearrangements of hydroxylamine derivatives. The sulfur atom of PhN(OH)SG is shown to provide an approximately 106 rate acceleration for N-O cleavage in a comparison with the Bamberger rearrangement of PhNHOH.
- Kazanis, Sophia,McClelland, Robert A.
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p. 3052 - 3059
(2007/10/02)
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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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- Metal Ion-Catalyzed Reduction of Substituted Nitrosobenzenes by 1-Benzyl-3,5-bis(1-pyrrolidinylcarbonyl)-1,4-dihydropyridine in Acetonitrile
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Metal ion catalyzed reduction of substituted nitrosobenzenes by 1-benzyl-3,5-bis(1-pyrrolidinylcarbonyl)-1,4-dihydropyridine (BPDH) in acetonitrile has been studied for seven bivalent metal ions.The reduction of N-methylacridinium salt (MA) has also been examined.In the former cases, it was found that the metal ions catalyze the reduction by forming a 1 : 1 complex with BPDH according to a Michaelis-Menten type saturation kinetics which allowed to derive the association constants, KM, for the complexation and the second-order rate constants, k2, for the reduction.A linear relationship was found between log k2 and the ionization potentials of metal ions with a positive slope.A linear Hammett relationship was also observed between log k2 and the Hammett ? constants with a positive p value for three metal ions.These results suggest that a bivalent metal ion is sandwiched between the BPDH and the substrate and acts as a Lewis acid to stabilize the incipient N-oxide anion of the substrate which is formed by hydride transfer in the transition state.In the cases of MA, all metal ions inhibited the reduction.Repulsion between the positive charges of the metal ion-BPDH complex and the substrate salt appears to be prevailing.
- Awano, Hiroshi,Takemoto, Kazuo,Ohya, Hirohisa,Tomio, Minaki,Tamagaki, Seizo,Tagaki, Waichiro
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p. 1887 - 1894
(2007/10/02)
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- Investigations on the Kinetics and Mechanism of Polarigraphic Reduction of o-, m- and p-Nitrotoluenes and o-, m- and p-Nitrophenols in the presence of Ionic and non-Ionic Surfactants
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Polarographic behaviour of o-, m- and p-nitrotoluenes (4percent, V/V, ethanolic solution) in the presence of ionic and non-ionic surfactants at their concentrations just sufficient to suppress the maxima has been studied as a function of pH of Britton-Robinson (BR) buffer.The present study aims at investigating the kinetics and mechanism of the reduction of these compounds at the d.m.e. which has been found to be diffusion-controlled and irreversible.The potential-dependent rate constant, kf,h has been calculated by Koutecky's method at different pH values of BR buffer and the values of kinetic parameters (αna and kf,h0) have been calculated from log kf,h Vs Ed.e. plots which are linear thereby suggesting that only a single rate-determining step is involved in the reduction of each depolarizer.Based on the values of kinetic parameter, αna and the variation of E1/2 with pH, the stoichiometry of the rate-determinig step, in each case, has been established thereby leading to the postulation of a mechanism for the polarographic reduction of each depolarizer.
- Singh, M.,Chandra, K.
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p. 977 - 989
(2007/10/02)
-
- 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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- Polarographic Studies on the Effect of Some Ionic and Non-ionic Surfactants on Kinetics of Irreversible Electrode Reactions of o-, m- and p-Nitrotoluenes
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Polarographic reduction of o-, m- and p-nitrotoluenes (in 4percent ethanolic solution) has been studied at 25 +/- 0.1 deg C in BR buffer of pH 7 in the presence of increasing amounts of some ionic and non-ionic surfactants.The reduction of all the three depolarizers is diffusion-controlled and irreversible.The kinetic parameters (αna and kfh0) of the electrode reactions have been calculated by Koutecky's method.The irreversible electrode reactions of o-, m- and p-nitrotoluenes tend to become increasingly more irreversible with increasing concentration of ionic and non-ionic surfactants.This is borne out by a decrease in kinetic parameters and id, and a negative shift in E1/2 with increasing concentrations of the surfactants.A tentative mechanism of the polarographic reduction of nitrotoluenes at pH 7 has also been proposed.This stipulates the protonation of the depolarizers in the steps preceding as well as succeeding the electrode reaction.The ease of reduction of three isomers at d.m.e. is in the order: meta > ortho > para.
- Chandra, Kailash,Shakya, Sarnam Singh,Singh, Mukhtar
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p. 254 - 258
(2007/10/02)
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