- The Reaction of Nitrogen Dioxide with N-Benzylidene-t-butylamine N-Oxide. Formation of a White Solid Adduct and Its Properties
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The reaction of N-benzylidene-t-butylamine N-oxide (PBN) with NO2 gave white diamagnetic solid C11H16N2O4 in addition to greenish blue free radical species.The white solid was shown to decompose quantitatively into the starting PBN and nitric acid when it was dissolved in water.
- Sonokawa, Koji,Machida, Hidenori,Sakakibara, Kazuhisa,Hirota, Minoru
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Read Online
- Control of methyl methacrylate radical polymerization via Enhanced Spin Capturing Polymerization (ESCP)
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The nitrone mediated polymerization of methyl methacrylate (MMA) via the enhanced (termination) spin capturing polymerization (ESCP) process is made possible via the addition of small amounts of styrene (between 5 and 10 vol.%) to the reaction mixture. Efficient control over the molecular weight between 7000 and 57,000 g mol-1 (at 60 °C) yields macromolecules that feature a mid-chain alkoxyamine functionality and are rich in methyl methacrylate. The collated kinetic and molecular weight data allow for a deduction of the spin capturing constant, CSC, in the range between 0.15 and 0.30. During the ESCP process, the number average molecular weight, Mn, of the formed mid-chain functional polymer is constant up to high monomer to polymer conversions (i.e. 80%). The high degree of alkoxyamine mid-chain functionality present in the generated polymeric material is evidenced via a subsequent nitroxide-mediated polymerization process employing the formed ESCP polymer, indicating a chain extension from 37,700 to 118,000 g mol-1 with a concomitant reduction in polydispersity (from 2.3 to 1.5).
- Zang, Lin,Wong, Edgar H.H.,Barner-Kowollik, Christopher,Junkers, Thomas
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Read Online
- Weak base-promoted selective rearrangement of oxaziridines to amidesviavisible-light photoredox catalysis
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The selective rearrangement of oxaziridines to amidesviaa single electron transfer (SET) pathway is unexplored. In this study, we present a weak base-promoted selective rearrangement of oxaziridines to amidesviavisible-light photoredox catalysis. The developed method shows excellent functional group tolerance with a broad substrate scope and good to excellent yields. Furthermore, control experiments and density functional theory (DFT) calculations are performed to gain insight into the reactivity and selectivity.
- Park, Jin,Park, Sehoon,Jang, Gwang Seok,Kim, Ran Hui,Jung, Jaehoon,Woo, Sang Kook
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p. 9995 - 9998
(2021/10/06)
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- Metal-Free Solvent Promoted Oxidation of Benzylic Secondary Amines to Nitrones with H2O2
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An environmentally benign protocol for the generation of nitrones from benzylic secondary amines via catalyst-free oxidation of secondary amines using H2O2 in MeOH or CH3CN is described. This methodology provides a selective access to a variety of C-aryl nitrones in yields of 60 to 93%. Several studies have been performed to shed light on the reaction mechanism and the role of the solvent.
- Adrio, Javier,Amarante, Giovanni Wilson,Granato, álisson Silva
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p. 13817 - 13823
(2021/10/01)
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- The effect of viscosity on the coupling and hydrogen-abstraction reaction between transient and persistent radicals
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The effect of viscosity on the radical termination reaction between a transient radical and a persistent radical undergoing a coupling reaction (Coup) or hydrogen abstraction (Abst) was examined. In a non-viscous solvent, such as benzene (bulk viscosity bulk 99% Coup/Abst selectivity, but Coup/Abst decreased as the viscosity increased (89/11 in PEG400 at 25 °C [bulk = 84 mPa s]). While bulk viscosity is a good parameter to predict the Coup/Abst selectivity in each solvent, microviscosity is the more general parameter. Poly(methyl methacrylate) (PMMA)-end radicals had a more significant viscosity effect than polystyrene (PSt)-end radicals, and the Coup/Abst ratio of the former dropped to 50/50 in highly viscous media (bulk = 3980 mPa s), while the latter maintained high Coup/ Abst selectivity (84/16). These results, together with the low thermal stability of dormant PMMA-TEMPO species compared with that of PSt-TEMPO species, are attributed to the limitation of the nitroxide-mediated radical polymerization of MMA. While both organotellurium and bromine compounds were used as precursors of radicals, the former was superior to the latter for the clean generation of radical species.
- Li, Xiaopei,Kato, Tatsuhisa,Nakamura, Yasuyuki,Yamago, Shigeru
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supporting information
p. 966 - 972
(2021/04/29)
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- S -Tetrazine: Robust and Green Photoorganocatalyst for Aerobic Oxidation of N,N-Disubstituted Hydroxylamines to Nitrones
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Efficient photocatalytic aerobic oxidative dehydrogenation reactions of N,N-disubstituted hydroxylamines to nitrones were developed with an in situ generated photocatalyst based on commercially available 3,6-dichlorotetrazine. This process affords a wide range of nitrones in high yields under mild conditions. In addition, an oxidative (3+3) cycloaddition between an oxyallyl cation precursor and a hydroxylamine was also developed.
- Allain, Clémence,Audebert, Pierre,Claraz, Aurélie,Le, Tuan,Lyu, Jiyuan,Masson, Géraldine
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supporting information
(2021/12/06)
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- Aliphatic nitro compounds chemistry: oximes–nitrones tunable production through directed tandem synthesis
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Abstract: Reduction of aliphatic nitro compounds in the presence of aldehydes and dialdehydes for tunable directed synthesis of oximes, nitrones, nitrone–oximes, and dinitrones was reported. The slow and nonselective reduction of aliphatic nitro compounds was directed by condensation of in situ prepared alkylhydroxylamines with aromatic aldehydes. Mononitrones and dinitrones were synthesized at reflux and at 55?°C conditions, respectively, in tetrahydrofuran using SnCl2?2H2O and Na2CO3. It was found that the presence of a catalytic amount of carboxylic acid such as 3-phenylpropanoic acid increases the yield of dinitrones versus nitrone–oxime and dioxime when dialdehydes were used as aldehyde source. Graphical abstract: [Figure not available: see fulltext.].
- Kazemi, Foad,Ramdar, Moosa,Davarpanah, Jamal
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p. 353 - 362
(2019/01/25)
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- Accessing benzooxadiazepines: Via formal [4 + 3] cycloadditions of aza- o -quinone methides with nitrones
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An unprecedented and efficient [4 + 3] cycloaddition of N-(ortho-chloromethyl)aryl amides with nitrones has been developed. This approach provides easy access to a series of seven-membered benzooxadiazepine derivatives in good to excellent yields (up to 99% yield) under mild reaction conditions.
- Zheng, Yong-Sheng,Tu, Liang,Gao, Li-Mei,Huang, Rong,Feng, Tao,Sun, Huan,Wang, Wen-Xuan,Li, Zheng-Hui,Liu, Ji-Kai
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p. 2639 - 2642
(2018/04/27)
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- Light-induced formation of nitroxyl radicals by organic Bi(V) compounds in the presence of 2-methyl-2-nitrosopropane and C-phenyl-N-tert-butylnitrone
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The organic bismuth compounds Ph3Bi(O2CCH=CHCH3)2 and Ph3Bi(O2CEt)2 decompose under scattered light in the presence of spin traps (2-methyl-2-nitrosopropane and C-phenyl-N-tert-butylnitrone) in organic solvents (acetonitrile, benzene, toluene) to form adducts of phenyl radicals with the traps.
- Gushchin,Kalistratova,Maleeva,Dodonov,Kosov, D. Yu.,Emel’yanov,Kuropatov
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p. 1547 - 1549
(2017/09/01)
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- Dual Role of Pyrrolidine and Cooperative Pyrrolidine/Pyrrolidinium Effect in Nitrone Formation
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The formation of nitrones by direct condensation between equimolecular amounts of N-substituted hydroxylamine hydrochlorides and aromatic or aliphatic aldehydes is efficiently promoted by pyrrolidine in a matter of minutes under very mild conditions in almost quantitative yields after a simple filtration through a short pad of silica gel. According to theoretical, spectroscopic, and experimental studies, this success is due to the ability of pyrrolidine to liberate the hydrochloride of the hydroxylamine and catalyze the reaction via iminium activation ion. Moreover, a cooperative pyrrolidine/pyrrolidinium chloride effect facilitates several steps of the catalytic cycle through proton transfer without hampering the nucleophilicity of the hydroxylamine by protonation.
- Morales, Sara,Guijarro, Fernando G.,Alonso, Inés,García Ruano, José Luis,Cid, M. Belén
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- Method for preparing nitrone from secondary amine
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The invention relates to a method for preparing nitrone from secondary amine. The method comprises the steps of adding 2 mmol of the secondary amine into a reactor, sequentially adding 4-5 mL of water, 0.02-0.03 mmol of tetrabutylammonium bromide, 0.02-0.08 mmol of a catalyst WO3-x and 3-6 mmol of a hydrogen peroxide solution with the concentration being 30-50%, and stirring the mixture for 2-6 hours at the temperature of 25-60 DEG C; or adding 2 mmol of the secondary amine into a reactor, adding 3-5 mL of polar solvent, 0.02-0.08 mmol of a catalyst WO3-x ad 3-6 mmol of a hydrogen peroxide solution with the concentration being 30-50%, and stirring the mixture for 2-6 hours at the temperature of 25-60 DEG C; diluting a mixed solution obtained after a reaction to 15-20 mL, conducting extraction, concentration and column chromatography isolation, and collecting a product. The catalyst adopted in the method is WO3-x nanosheets having oxygen vacancies and is high in catalytic oxidation activity; raw materials of the method are wide in source, the reaction condition is simple, the reaction temperature is low, the nitrone yield is high, and water serves as reaction solvent, so that the whole reaction steps are free of pollution, environmentally friendly and low in cost, high industrial application value is achieved, and in addition, great environmental and social significance is achieved.
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Paragraph 0017
(2016/11/28)
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- Iridium-Catalyzed Direct C-H Sulfamidation of Aryl Nitrones with Sulfonyl Azides at Room Temperature
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Ir(III)-catalyzed direct C-H sulfamidation of aryl nitrones has been developed to synthesize various sulfamidated nitrones in moderate to excellent yields with excellent regioselectivity and broad functional group tolerance. This transformation could proceed smoothly at room temperature with low catalyst loading in the absence of external oxidants, acids, or bases. Molecular nitrogen was released as the sole byproduct, thus providing an environmentally benign sulfamidation process. And this protocol could efficiently apply to synthesize the substituted benzisoxazoline via one-step transformation from the product.
- Pi, Chao,Cui, Xiuling,Wu, Yangjie
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p. 7333 - 7339
(2015/08/18)
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- Organotin-oxotungstate coordination polymer: An efficient catalyst for the selective oxidation of amines
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The organometallic coordination polymer [(nBu3Sn)2WO4] catalyzed the selective oxidation of secondary and primary amines to nitrones and oximes, respectively. The catalyst was found to be reusable for five catalytic cycles without any appreciable loss in activity. Under the optimized reaction conditions [4 mol% catalyst, 3-4 equiv of hydrogen peroxide (30 wt%, aqueous solution), methanol as the solvent, r.t.], the corresponding nitrones and oximes were obtained with good efficiency.
- Nikbakht, Fatemeh,Heydari, Akbar
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p. 132 - 136
(2015/03/04)
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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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- Aerobic oxidation of hydroxylamines with nanoporous gold catalyst as an efficient synthetic method of nitrones Dedicated to Professor Jiro Tsuji on the occasion of his receipt of the 2014 Tetrahedron Prize
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Abstract A facile preparation of nitrones has been achieved by use of unsupported nanoporous gold (AuNPore) as a heterogeneous catalyst through aerobic oxidation of N,N-disubstituted hydroxylamines with molecular oxygen as an oxidizing agent under mild conditions. A variety of amines were oxidized to the corresponding nitrones in high chemical yields. The catalyst is robust enough to be reused without leaching.
- Yudha S, Salprima,Kusuma, Indra,Asao, Naoki
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p. 6459 - 6462
(2015/08/18)
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- Trichloroacetonitrile-hydrogen peroxide: A simple and efficient system for the selective oxidation of tertiary and secondary amines
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A variety of tertiary and secondary amines were efficiently oxidized to their corresponding N-oxides and nitrones, respectively, using the trichloroacetonitrile-hydrogen peroxide system. The in situ generated trichloromethylperoxyimidic acid is the active reagent for the oxidation processes.
- Nikbakht, Fatemeh,Heydari, Akbar
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p. 2513 - 2516
(2014/05/06)
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- O-trifluoromethylation of N,N-disubstituted hydroxylamines with hypervalent iodine reagents
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A mild trifluoromethylation reaction of N,N-disubstituted hydroxylamines that is tolerant towards a variety of functional groups, including nitriles, alcohols, ketones, esters, amides, imides, and nitrogen heterocycles, is reported. The key feature of this reaction is the activation of the CF 3 reagent with either trimethylsilyl triflate or LiClO4 and partial or full deprotonation of the substrate with tetramethylguanidine or lithium diisopropylamide. Products were obtained in up to 80 % yield. Preliminary mechanistic studies suggested that the reaction follows a radical pathway in which the deprotonated hydroxylamine and a Lewis or Bronsted acid activated CF3 reagent engages in a single-electron-transfer step to generate a pair of radicals that recombine to afford the desired product. The trifluoromethylation procedure was successfully used in the modification of secondary nitrogen groups of pharmaceutically relevant targets (Fluoxetine and Mefloquine), which afforded new derivatives containing a novel N-trifluoromethoxy moiety. Copyright
- Matousek, Vaclav,Pietrasiak, Ewa,Sigrist, Lukas,Czarniecki, Barbara,Togni, Antonio
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supporting information
p. 3087 - 3092
(2014/06/09)
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- Grafting of a rhenium-oxo complex on Schiff base functionalized graphene oxide: An efficient catalyst for the oxidation of amines
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A rhenium-oxo complex such as methyltrioxorhenium (MTO) has been homogeneously immobilized on a Schiff base modified graphene oxide (GrO) support via covalent bonding. The loading of MTO on GrO nanosheets was monitored by FTIR, TG-DTA, and elemental analyses. The developed heterogeneous catalyst is found to be efficient for the oxidation of various amines to the corresponding N-oxides using hydrogen peroxide as an oxidant in high to excellent yields. At the end of the reaction, the catalyst is readily recovered by filtration and reused for subsequent runs. After the third run, the catalyst showed a marginal decrease in catalytic activity owing to the leaching of the MTO complex from the support. This journal is the Partner Organisations 2014.
- Khatri, Praveen K.,Choudhary, Shivani,Singh, Raghuvir,Jain, Suman L.,Khatri, Om P.
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p. 8054 - 8061
(2014/05/20)
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- Stereoselective synthesis of fluoroalkenoates and fluorinated isoxazolidinones: N-substituents governing the dual reactivity of nitrones
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α-Fluoroalkenoates and 4-fluoro-5-isoxazolidinones are of vast interest due to their potential biological applications. We now demonstrate the syntheses of (E)-α-fluoroalkenoates and 4-fluoro-5-isoxazolidinones by the reactions between nitrones and α-fluoro-α-bromoacetate. By altering N-substituents in nitrones, (E)-α-fluoroalkenoates and 4-fluoro-5-isoxazolidinones can be achieved, respectively, with high chemo- and stereoselectivities. Experimental and computational studies have been conducted to elucidate the reaction mechanisms. Linear free energy relationship studies further revealed that the N-substituent effects are primarily of electronic origin. Copyright
- Prakash, G.K. Surya,Zhang, Zhe,Wang, Fang,Rahm, Martin,Ni, Chuanfa,Iuliucci, Marc,Haiges, Ralf,Olah, George A.
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supporting information
p. 831 - 838
(2014/01/23)
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- Activation of C-H bonds in nitrones leads to iridium hydrides with antitumor activity
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We report the design and synthesis of a series of new cyclometalated iridium hydrides derived from the C-H bond activation of aromatic nitrones and the biological evaluation of these iridium hydrides as antitumor agents. The nitrone ligands are based on the structure of a popular antioxidant, α-phenyl-N-tert-butylnitrone (PBN). Compared to cisplatin, the iridium hydrides exhibit excellent antitumor activity on HepG2 cells. The metal-coordinated compound with the most potent anticancer activity, 2f, was selected for further analysis because of its ability to induce apoptosis and interact with DNA. During in vitro studies and in vivo efficacy analysis with tumor xenograft models in Institute of Cancer Research (ICR) mice, complex 2f exhibited antitumor activity that was markedly superior to that of cisplatin. Our results suggest, for the first time, that metal hydrides could be a new type of metal-based antitumor agent.
- Song, Xiaoda,Qian, Yong,Ben, Rong,Lu, Xiang,Zhu, Hai-Liang,Chao, Hui,Zhao, Jing
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supporting information
p. 6531 - 6535
(2013/09/23)
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- Oxidation of secondary amines to nitrones using magnetically separable tungstophosphoric acid supported on silica-encapsulated γ-Fe 2O3 nanoparticles
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Superparamagnetic tungstophosphoric acid supported on silica-encapsulated γ-Fe2O3 was used as an efficient catalyst for the direct oxidation of secondary amines to nitrones with hydrogen peroxide as the oxidant. The catalyst could be recycled up to four times without significant loss of activity.
- Nikbakht, Fatemeh,Heydari, Akbar,Saberi, Dariush,Azizi, Kobra
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p. 6520 - 6523
(2013/11/19)
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- Methyltrioxorhenium-catalysed oxidation of secondary amines to nitrones in ionic liquids
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Nitrones serve as starting materials for the synthesis of many heterocycles. Oxidation of secondary amines using hydrogen peroxide and the catalytic amount of methyltrioxorhenium in ionic liquids is a useful method for the preparation of nitrones. Ultrasonic irradiation and ionic liquids have a positive influence on the reaction. The nitrones required were isolated in good yields. Corresponding hydroxylamines, which can be easily oxidised to nitrones, often accompanied the main products. Methyltrioxorhenium in ionic liquids was re-used in several reaction cycles without any deteriorating effect on the course of the reaction.
- Meciarova, Maria,Mojzesova, Melinda,Sebesta, Radovan
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p. 51 - 58,8
(2020/08/20)
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- Microwave-assisted synthesis of hydroxyphenyl nitrones with protective action against oxidative stress
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Oxidative stress plays an important role in neuronal death in neurodegenerative disorders such as Parkinson's disease (PD). Hydroxyphenyl nitrones, derivatives of the nitrone spin trap alpha-phenyl-N-tert-butylnitrone (PBN), were synthesized and their antioxidant, anti-inflammatory and neuroprotective activity in neural cells evaluated. These hydroxyphenyl nitrones 5-7 were synthesized by reaction of the corresponding hydroxybenzaldehyde with N-tert-butyl hydroxylamine under microwave irradiation. They showed good peroxyl free radical scavenger capacities, analyzed by oxygen radical absorbance capacity (ORAC). Also inhibited peroxynitrite-mediated tyrosine nitration of alpha-synuclein in vitro and protected human neuroblastoma (SH-SY5Y) cells against SIN-1 and 6-OHDA toxicity when micromolar concentrations were used. Besides, the hydroxyphenyl nitrones evaluated showed anti-inflammatory activity modulating nitrite production in primary neural cell cultures of astrocytes and microglia treated with lipopolysaccharide (LPS), a potent inflammatory agent. These experimental data suggest a potential therapeutic use of these hydroxyphenyl nitrones against oxygen and nitrogen reactive species involved in neurodegenerative pathology.
- Chavarría, Cecilia,Perez, Daniel I.,Pérez, Concepción,Morales Garcia, Jose A.,Alonso-Gil, Sandra,Pérez-Castillo, Ana,Gil, Carmen,Souza, José M.,Porcal, Williams
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supporting information
p. 44 - 49
(2013/02/23)
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- Synthesis, structure, theoretical and experimental in vitro antioxidant/pharmacological properties of α-aryl, N-alkyl nitrones, as potential agents for the treatment of cerebral ischemia
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The synthesis, structure, theoretical and experimental in vitro antioxidant properties using the DPPH, ORAC, and benzoic acid, as well as preliminary in vitro pharmacological activities of (Z)-α-aryl and heteroaryl N-alkyl-nitrones 6-15, 18, 19, 21, and 23, is reported. In the in vitro antioxidant activity, for the DPPH radical test, only nitrones bearing free phenol groups gave the best RSA (%) values, nitrones 13 and 14 showing the highest values in this assay. In the ORAC analysis, the most potent radical scavenger was nitrone indole 21, followed by the N-benzyl benzene-type nitrones 10 and 15. Interestingly enough, the archetypal nitrone 7 (PBN) gave a low RSA value (1.4%) in the DPPH test, or was inactive in the ORAC assay. Concerning the ability to scavenge the hydroxyl radical, all the nitrones studied proved active in this experiment, showing high values in the 94-97% range, the most potent being nitrone 14. The theoretical calculations for the prediction of the antioxidant power, and the potential of ionization confirm that nitrones 9 and 10 are among the best compounds in electron transfer processes, a result that is also in good agreement with the experimental values in the DPPH assay. The calculated energy values for the reaction of ROS (hydroxyl, peroxyl) with the nitrones predict that the most favourable adduct-spin will take place between nitrones 9, 10, and 21, a fact that would be in agreement with their experimentally observed scavenger ability. The in vitro pharmacological analysis showed that the neuroprotective profile of the target molecules was in general low, with values ranging from 0% to 18.7%, in human neuroblastoma cells stressed with a mixture of rotenone/oligomycin-A, being nitrones 18, and 6-8 the most potent, as they show values in the range 24-18.4%.
- Samadi, Abdelouahid,Soriano, Elena,Revuelta, Julia,Valderas, Carolina,Chioua, Mourad,Garrido, Ignacio,Bartolomé, Bego?a,Tomassolli, Isabelle,Ismaili, Lhassane,González-Lafuente, Laura,Villarroya, Mercedes,García, Antonio G.,Oset-Gasque, María J.,Marco-Contelles, José
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experimental part
p. 951 - 960
(2011/03/19)
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- Effective oxidation of secondary amines to nitrones with alkyl hydroperoxides catalysed by (Trialkanolaminato)titanium(IV) complexes
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The effective catalytic oxidation of secondary amines to nitrones with, alkyl hydroperoxides as the primary oxidants is described. The titanium, alkoxi.de catalysts are protected. from the water co-product by the combined use of a tightly binding trialkanolamine ligand and molecular sieves. Nitrones can be obtained in high yields (up to 98%) under homogeneous, anhydrous conditions and even in the absence of solvent. The reactions are fast (2-7 h) and good selectivity and complete conversion can be achieved with as little as 1 % catalyst.
- Forcato, Massimiliano,Mba, Miriam,Nugent, William A.,Licini, Giulia
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experimental part
p. 740 - 748
(2010/03/26)
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- Condensed oxaziridine-mediated [3+2] cycloaddition: Synthesis of polyhetero-bicyclo compounds
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Polyhetero-bicyclo compounds were synthesized by a regioselective [3+2]-cycloaddition reaction between stable condensed oxaziridines and alkenes, alkynes, and nitriles. These molecules showed considerable antimicrobial activity against several gram-positive bacteria.
- Videtta, Valeria,Perrone, Serena,Rosato, Francesca,Alifano, Pietro,Tredici, Salvatore M.,Troisi, Luigino
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scheme or table
p. 2781 - 2783
(2010/12/25)
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- A torquoselective extrusion of isoxazoline N-oxides. Application to the synthesis of aryl vinyl and divinyl ketones for Nazarov cyclization
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A mild, convenient reaction sequence for the synthesis of Nazarov cyclization substrates is described. The [3+2] dipolar cycloaddition of a nitrone and an electron-deficient alkyne gives an isolable isoxazoline intermediate, which upon oxidation undergoes stereoselective extrusion of nitrosomethane to give aryl vinyl or divinyl ketones.
- Canterbury, Daniel P.,Herrick, Ildiko R.,Um, Joann,Houk,Frontier, Alison J.
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experimental part
p. 3165 - 3179
(2009/09/05)
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- Nafion supported molybdenum oxychloride: Recyclable catalyst for one-pot synthesis of nitrones via direct condensation/oxidation of primary amines and aldehydes using UHP as oxidant
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Immobilization of molybdenum(vi) oxychloride to the surface of perfluorinated ion-exchange polymer "Nafion"via an ion exchange method was carried out for the first time. The prepared Nafion immobilized molybdenum(vi) oxychloride catalyst was used for the direct synthesis of nitrones via one-pot condensation/oxidation of primary amines with aldehydes using solid urea-hydrogen peroxide (UHP) as oxidant under very mild reaction conditions. The developed polymer immobilized catalyst showed better activity than its analogous homogeneous catalyst with the added benefits of facile recovery and recyclability of the catalyst without leaching and loss in catalytic activity.
- Singh, Bhawan,Jain, Suman L.,Khatri, Praveen K.,Sain, Bir
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scheme or table
p. 1941 - 1944
(2010/06/15)
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- C3-symmetric titanium(IV) triphenolate amino complexes for a fast and effective oxidation of secondary amines to nitrones with hydrogen peroxide
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The efficient catalytic oxidation of secondary amines to nitrones using hydrogen peroxide as primary oxidant is described. The titanium(IV) complex 2 bearing a C3-symmetrical triphenolate amino ligand has proved to be an air- and water-tolerant complex that efficiently catalyzes secondary amine oxidations at 60°C without previous activation [catalyst loading as low as 0.01%, yields up to 99%, turnover numbers (TONs) up to 8000 and turnover frequencies (TOFs) up to 11000 h-1).
- Zonta, Cristiano,Cazzola, Elisa,Mba, Miriam,Licini, Giulia
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experimental part
p. 2503 - 2506
(2009/09/07)
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- Solvent-free synthesis of nitrones in a ball-mill
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Various C-aryl and C-alkyl-nitrones were synthesized within 0.5-2 h via condensation of an equimolar amount of aldehydes and N-substituted-hydroxylamines under solvent-free conditions in?a ball-mill apparatus. Reactions can be performed without the need of excluding air and moisture and yields the expected products with no need for further purification. The study has been complemented by Differential Scanning Calorimetry (DSC) and solid-state 13C MAS nuclear magnetic resonance experiments. We have also studied the temperature profile during the reaction. A comparative study with the corresponding solvent-free microwave activated reaction showed the superiority of the ball-milling method; 31 examples are described, including the synthesis of the anti-aging agent C-phenyl-N-tert-butyl nitrone (PBN) and one of its analogues C-2-pyridyl-N-tert-butylnitrone (2-PyBN).
- Colacino, Evelina,Nun, Pierrick,Colacino, Francesco Maria,Martinez, Jean,Lamaty, Frédéric
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p. 5569 - 5576
(2008/09/21)
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- Exploiting microwave-assisted neat procedures: synthesis of N-aryl and N-alkylnitrones and their cycloaddition en route for isoxazolidines
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Microwave irradiation allows increasing the speed of several reactions and also offers the possibility of eliminating poisoning organic solvents. In this work we report the microwave-assisted neat synthesis of α-phenyl-tert-butylnitrone (PBN) and other alkyl and aryl nitrones and also the rapid synthesis of isoxazolidines resulting from 1,3-dipolar cycloaddition of nitrones to ethyl trans-crotonate.
- Andrade, Marta M.,Barros, Maria Teresa,Pinto, Rui C.
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p. 10521 - 10530
(2008/12/23)
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- Synthesis of new 3,5-diarylisoxazolidines by cycloaddition of oxaziridines and alkenes
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This article reports a novel process of cycloaddition of C-aryloxaziridines with a variety of alkenes to afford stable, five-membered heterocycles 13-24. The steric hindrance of the tert-butyl group on the nitrogen atom of the oxaziridine is responsible for the high stereoselectivity of the cycloaddition reaction.
- Fabio, Marilena,Ronzini, Ludovico,Troisi, Luigino
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p. 12896 - 12902
(2008/03/27)
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- Ti(IV)/trialkanolamine catalytic polymeric membranes: Preparation, characterization, and use in oxygen transfer reactions
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New heterogeneous oxidation catalysts have been obtained by entrapping Ti(IV)/trialkanolamine complexes within polymeric membranes. The catalytic membranes were prepared by a nonsolvent-induced phase-inversion technique. Three polymers, polyvinylidene fluoride (PVDF), a modified polyetherketone (PEEK-WC), and polyacrylonitrile (PAN), with different functional groups and chemical-physical properties, were used to tune the reactivity of the catalytic polymeric membranes in the stereoselective oxidation to sulfoxide and chemoselective oxidation of secondary amines to nitrones by alkyl hidroperoxides. The chemical-physical analysis of the new catalytic membranes was carried out by SEM, EDX, IR, CAM, and XPS techniques. In particular, the XPS spectra showed a very interesting orientation effect of PVDF membranes on the entrapped Ti(IV)/trialkanolamine complex. PVDF-based catalytic membranes gave the best results, affording products in shorter reaction times, higher yields, and better selectivity compared with the corresponding homogeneous systems. The membranes can be recycled up to five runs with no loss of activity.
- Buonomenna, Maria Giovanna,Drioli, Enrico,Bertoncello, Renzo,Milanese, Laura,Prins, Leonard J.,Scrimin, Paolo,Licini, Giulia
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p. 221 - 231
(2007/10/03)
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- COMPOSITIONS COMPRISING A NITRONE COMPOUND FOR USE IN TREATING UVEITIS
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Ophthalmic pharmaceutical compositions containing a pharmaceutically acceptable ophthalmic carrier and an inflammation-treating amount of a nitrone compound are disclosed. Also disclosed are methods for treating ocular inflammation conditions, such as uveitis, using pharmaceutical compositions.
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- Oxidation of secondary amines by molecular oxygen and cyclohexanone monooxygenase
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Cyclohexanone monooxygenase from Acinetobacter calcoaceticus catalyzed the oxidation of tertiary and secondary amines to N-oxides and nitrones, respectively. The formation of a hydroxylamine intermediate was involved with secondary amines as starting substrates.
- Colonna, Stefano,Pironti, Vincenza,Carrea, Giacomo,Pasta, Piero,Zambianchi, Francesca
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p. 569 - 575
(2007/10/03)
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- PREPARATION OF NITRONE DERIVATIVES
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Nitrone derivatives are efficiently prepared by increasing reagent concentrations in reaction solutions. Aldehydes and amines may be condensed to prepare an imine intermediate. Elimination of the solution media generally renders the imine formation more efficient. The imine is then reacted with a peroxysulfate oxidizing agent in a solution having at least about 0.1M concentration of the imine. The oxaziridine is rearranged to produce the nitrone derivative in high yield and good purity.
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- Ti(IV)-based catalytic membranes for efficient and selective oxidation of secondary amines
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The incorporation of homogenous Ti(IV)/trialkanolamine catalyst in polymeric membranes provided new polymeric catalytic Ti(IV)-based membranes, stable and efficient as heterogeneous catalysts for chemoselective oxidations of secondary amines to nitrones by alkyl hydroperoxides. Polyvinylidene fluoride (PVDF)-based catalytic membranes gave the best results affording products in short reaction times, high yields and selectivity using as little as 1% of catalyst, comparable with the performances of the corresponding homogeneous system. PVDFa€"Ti membrane could be recycled up to five runs with no loss of activity.
- Buonomenna, Maria Giovanna,Drioli, Enrico,Nugent, William A.,Prins, Leonard J.,Scrimin, Paolo,Licini, Giulia
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p. 7515 - 7518
(2007/10/03)
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- A 'waterproof' catalyst for the oxidation of secondary amines to nitrones with alkyl hydroperoxides
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Catalytic oxidation of secondary amines to nitrones using alkyl hydroperoxides as primary oxidant has been demonstrated for the first time. The titanium alkoxide catalyst is protected from co-product water by the combined use of a tightly binding trialkanolamine ligand and molecular sieves. Nitrones can be obtained in high yield (up to 98%) under homogeneous, anhydrous conditions and even in the absence of solvent. The reactions are fast (2-7 h) and good selectivity can be achieved with as little as 1% catalyst.
- Forcato, Massimiliano,Nugent, William A.,Licini, Giulia
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- A novel route to substituted 4-methylene-4,5-dihydroisoxazoles mediated by hafnium(IV) chloride
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Heating alkyl vinyl ketones and N-tert-butylarylmethylide-neamine N-oxides in the presence of HfCl4 results in the formation of 4-methylene-4,5-dihydroisoxazoles in good yield.
- Dunn,Graham,Grigg,Higginson,Sridharan,Thornton-Pett
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p. 1968 - 1969
(2007/10/03)
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- Two new methodologies for the deoxygenation and reduction of nitrones based on the use of lithium and DTBB (cat.)
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A variety of nitrones undergo deoxygenation when treated with an excess of lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB) (10 mol%) in THF at room temperature to give the corresponding imines. The Li/DTBB system, when combined with nickel(II) chloride dihydrate allows the reduction of a series of nitrones to secondary amines. The use of the deuterium oxide-containing nickel(II) salt transforms the starting nitrones to deuterated secondary amines.
- Radivoy,Alonso,Yus
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p. 427 - 430
(2007/10/03)
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- One-pot synthesis of functionalized nitrones from nitro compounds
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The zinc-mediated reduction of nitroalkanes and nitroarenes in the presence of aldehydes is an efficient method to synthesize a wide range of nitrones. This method is mild enough to accommodate a variety of functional groups. It is particularly useful when the intermediate hydroxylamines are unstable and/or water-soluble. We used it to prepare several aromatic, aliphatic and highly functionalized sugar-derived nitrones.
- Gautheron-Chapoulaud,Pandya,Cividino,Masson,Py,Valle?e
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p. 1281 - 1283
(2007/10/03)
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- EPR Kinetic Evidence for Radical Intermediacy in the Oxidation of Secondary Amines to Nitrones by [Wo(O2)2OCOC5H4N]- [Bu4N+]
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Oxidation reactions of N,N-benzylalkylamines by [WO(O2)2OCOC5H4N] -[Bu4N+] to nitrones were kinetically studied by UV and EPR techniques. The reactions follow a second-order rate law and the rate-determining step is a simple bimolecular attack of amine onto the peroxide oxygen of the peroxometal complex, which leads to the formation of the corresponding hydroxylamine. However, EPR measurements and iterative procedures point out that the reaction occurs through the intermediacy of aminoxyl radicals, formed by oxidation of hydroxylamine generated in situ in the rate-determining step, and subsequent oxidations of these radicals to nitrones by the starting peroxo complex. It is suggested that the oxidation of hydroxylamine to aminoxyl radical as well as the oxidation of aminoxyl radical to nitrone occurs through an electron transfer step associated with a proton transfer.
- Ballistreri,Bianchini,Pinzino,Tomaselli,Toscano
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p. 2710 - 2715
(2007/10/03)
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- Increased intensity of tert-butoxyl radical emission in 4-chloro-2- methylphenoxyacetic acid (MCPA) synthesis
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The important herbicide, 2-methyl-4-chlorophenoxyacetic acid (MCPA) was synthesized by the chlorination of 2-methylphenoxyacetic acid with tert-butyl hypochlorite in the presence of methyl N,N-dimethylglycinate as a catalyst, giving a high yield and regioselectivity. The reaction was investigated using the spin-trapping technique in electron paramagnetic resonance measurement conditions, with nitrosodurene as a spin trap. Increased intensity emission of the tert-butoxyl radical (2.9 times in relation to the starting level) was observed after the catalyst had been introduced into the reaction mixture, indicating a free radical mechanism for the reaction.
- Jezierski, Adam,Zakrzewski, Jerzy,Moszczyski, Wiesaw
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p. 1229 - 1232
(2007/10/03)
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- Reaction of 2-tert-butyl-3-phenyloxaziridine with alkyl isothiocyanates and its application to glucosylaminoheterocycle synthesis
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2-tert-Butyl-3-phenyloxaziridine was heated with alkyl isothiocyanates to afford 4-alkyl-2-tert-butyl-3-phenyl-l,2,4-oxadiazolidine-5-thiones. The reaction mechanism of the ring formation was discussed. This reaction was applicable to synthesis of glucosylaminoheterocycles.
- Shimizu, Masao,Gama, Yasuo,Shibuya, Isao
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p. 1935 - 1941
(2007/10/03)
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- Oxidation of sulfides to sulfoxides with 3-aryl-2-tert-butyloxaziridines under high pressure
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3-Phenyl-2-tert-butyloxaziridine has been shown to behave as an oxidant under 800 MPa at 100°C to oxidize sulfides to sulfoxides, in spite of having been reported to be inactive as an oxidant and to undergo thermal rearrangement to W-tert-butyl-α-phenylnitrone at atmospheric pressure. It has been shown that under thermal and high-pressure conditions the ability of the oxaziridine to react changes dramatically. The mechanism for the high-pressure reaction is also discussed.
- Shimizu, Masao,Shibuya, Isao,Taguchi, Yoichi,Hamakawa, Satoshi,Suzuki, Kunio,Hayakawa, Takashi
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p. 3491 - 3492
(2007/10/03)
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- Methyltrioxorhenium-Catalyzed Oxidation of Secondary and Primary Amines with Hydrogen Peroxide
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The methyltrioxorhenium-catalyzed oxidation of secondary amines and primary amines with hydrogen peroxide has been carried out. The oxidation of secondary amines afforded nitrones in good-to-excellent yield. Benzylamines were selectively oxidized to oximes, while general primary alkylamines possessing the α-C -H bond gave mixtures of oximes, nitroso dimers, and azoxy compounds.
- Yamazaki, Shigekazu
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p. 877 - 883
(2007/10/03)
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- Multiplicity of reaction pathways in the processes of oxygen transfer to secondary amines by Mo(VI) and W(VI) peroxo complexes
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Oxidation of N,N-benzylmethylamine, N,N-benzylisopropylamine, and N,N-benzyl-tert-butylamine by both anionic and neutral Mo(VI) and W(VI) oxodiperoxo complexes yields the corresponding nitrones quantitatively. The oxidation reactions employing anionic oxidants were performed in CHCl3 and follow second-order kinetics, first order with respect to the amine and to the oxidant. The data were rationalized on the basis of a rate-determining nucleophilic attack of the amine onto the peroxide oxygen of the oxidant, with a transition state in which N-O bond formation and O-O bond cleavage occur in a concerted way (electrophilic oxygen transfer mechanism). This attack yields the corresponding hydroxylamine, which then is furtherly oxidized to nitrone in a fast step. On the other hand, in the case of neutral oxidants 1H-NMR data as well as kinetic data indicate that amine coordinates the metal center replacing the original ligand HMPA and yields a new peroxo complex. For N,N-benzyl-tert-butylamine such a complex was isolated and characterized. These new peroxo complexes can themselves behave as electrophilic oxidants, transferring oxygen to external amine molecules through the same pathway followed by anionic oxidants, or can yield the reaction product by intramolecular oxidation of the coordinate amine. Measurements of added HMPA effects on oxidation rate would seem more consistent with the electrophilic oxygen transfer mechanism.
- Ballistreri, Francesco P.,Barbuzzi, Elena G. M.,Tomaselli, Gaetano A.,Toscano, Rosa M.
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p. 6381 - 6387
(2007/10/03)
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- Synthesis of nitrones using the methyltrioxorhenium/hydrogen peroxide system
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Secondary amines are oxidized by the methyltrioxorhenium/hydrogen peroxide system to the corresponding nitrones in excellent yield. The results provide a further example of the parallel between the chemistry of this metal system and that of the dioxiranes.
- Murray, Robert W.,Iyanar, Kaliappan,Chen, Jianxin,Wearing, James T.
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p. 8099 - 8102
(2007/10/03)
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- Synthesis of nitrones by methyltrioxorhenium catalyzed direct oxidation of secondary amines
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Oxidation of secondary amines catalyzed by methyltrioxorhenium (MTO) with H2O2 or urea-hydrogen peroxide complex (UHP) at room temperature gives the corresponding nitrones in good yields.
- Goti, Andrea,Nannelli, Luca
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p. 6025 - 6028
(2007/10/03)
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- Regiochemistry of mercury(II) oxide oxidation of unsymmetrical N,N-disubstituted hydroxylamines
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Mercury(II) oxide oxidation of N,N-disubstituted hydroxylamines with the α and α' carbon atoms containing one and two hydrogen atoms, respectively, gave aldonitrones in a highly regioselective manner. Removal of the α proton is involved in the rate determining step as shown by primary kinetic isotope effect.
- Ali, Sk. Asrof,Hashmi, S. M. Azhar,Siddiqui, Mohammad N.,Wazeer, Mohammed I. M.
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p. 14917 - 14928
(2007/10/03)
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