- An FTIR spectroscopic study of the selective oxidation of nitrosobenzne to nitrobenzene by metal oxides
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Catalytic conversion of nitro- into nitrosobenzene by transition metal oxides is of considerable practical and theoretical interest. Therefore, the surface chemistry of nitrosobenzene on various metal oxides has been studied using IR spectroscopy. The main products of surface reactions are nitrobenzene and azoxybenzene. Findings of this study are compared with the results of a mass spectroscopic study carried out with nitrosobenzene on the same oxides. Molecularly adsorbed nitrosobenzene is found to be coordinated to metal cations by σ-N as well as σ-O bonds. Also the cis-dimer of nitrosobenzene is detected. As a reference, the spectra of adsorbed nitrosobenzene were compared with the spectra of monomeric nitrosobenzene dissolved in benzene and dimeric nitrosobenzene dissolved in ethanol. Some IR absorptions not reported earlier are assigned to C-N stretching and ring vibrations of σ-O coordinated and dimeric nitrosobenzene. The coordination modes of nitrosobenzene observed with the different oxides, and the reverse relationship found between ν(N=O) and ν(C-N) are in agreement with the observations made with nitroso compounds coordinated as ligands in organometallic complexes. A link to the catalytic behavior of nitrosobenzene on oxides is indicated.
- Meijers,Ponec
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- A novel intermediate in allylic amination catalyzed by iron salts
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Our initial probe of the aminations catalyzed by iron salts excluded the intermediacy of free ArNO, suggesting that a coordinated organonitrogen species could be the active aminating agent. To elucidate the mechanism of these latter reactions we report herein (a) the isolation and first structural elucidation of a metal complex of a C-nitroso dimer (1), and (b) evidence that this novel compound is the key aminating agent in allylic aminations catalyzed by iron salts. We have established with 1 the first structurally verified metal complex of a C-nitroso dimer and its unprecedented reactivity and selectivity for the allylic N-functionalization of olefins. Its involvement as the aminating agent in FeX2,3-catalyzed allylic amination also has been strongly implicated.
- Srivastava,Khan,Nicholas
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- Concerning the baker's yeast (Saccharomyces cerevisiae) mediated reduction of nitroarenes and other N-O containing functional groups
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Nitro- and nitrosoarenes can be reduced using baker's yeast (Saccharomyces cerevisiae) under two distinct sets of conditions, one of which is in fact a well established non-enzymic process. In order to clarify reports in the literature a comparison of the two methods has been made.
- Blackie, Josie A.,Turner, Nicholas J.,Wells, Andrew S.
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- MARKED METAL ION EFFECTS IN ELECTRON TRANSFER FROM REDUCED FLAVIN TO AROMATIC NITRO COMPOUNDS IN ETHANOL
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The reduction of p-chloronitrobenzene by a reduced flavin has been investigated kinetically in the presence of divalent metal ions in EtOH under anaerobic conditions.A large rate acceleration due to the metal ions was observed; 1(none) : 32 Zn(2+) : 420 Ni(2+) : 1 000 Co(2+) : 12 Mn(2+).The role of the metal ions is proposed.The reducing ability of metal-chelated flavin radicals has been briefly examined by employing 2,4-dinitrochlorobenzene as an electron acceptor.
- Yano, Yumihiko,Sakaguchi, Terukiyo,Nakazato, Michiaki
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- Zr(OH)4-Catalyzed Controllable Selective Oxidation of Anilines to Azoxybenzenes, Azobenzenes and Nitrosobenzenes
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The selective oxidation of aniline to metastable and valuable azoxybenzene, azobenzene or nitrosobenzene has important practical significance in organic synthesis. However, uncontrollable selectivity and laborious synthesis of the expensive required catalysts severely hinders the uptake of these reactions in industrial settings. Herein, we have pioneered the discovery of Zr(OH)4 as an efficient heterogeneous catalyst capable of the selective oxidation of aniline, using either peroxide or O2 as oxidant, to selectively obtain various azoxybenzenes, symmetric/unsymmetric azobenzenes, as well as nitrosobenzenes, by simply regulating the reaction solvent, without the need for additives. Mechanistic experiments and DFT calculations demonstrate that the activation of H2O2 and O2 is primarily achieved by the bridging hydroxyl and terminal hydroxyl groups of Zr(OH)4, respectively. The present work provides an economical and environmentally friendly strategy for the selective oxidation of aniline in industrial applications.
- Long, Yu,Luo, Nan,Ma, Jiantai,Qin, Jiaheng,Sun, Fangkun,Wang, Wei David,Zhou, Pan-Pan
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supporting information
(2021/12/09)
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- NaI/PPh3-Mediated Photochemical Reduction and Amination of Nitroarenes
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A mild transition-metal- and photosensitizer-free photoredox system based on the combination of NaI and PPh3 was found to enable highly selective reduction of nitroarenes. This protocol tolerates a broad range of reducible functional groups such as halogen (Cl, Br, and even I), aldehyde, ketone, carboxyl, and cyano. Moreover, the photoredox catalysis with NaI and stoichiometric PPh3 provides also an alternative entry to Cadogan-type reductive amination when o-nitrobiarenes were used.
- Qu, Zhonghua,Chen, Xing,Zhong, Shuai,Deng, Guo-Jun,Huang, Huawen
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supporting information
p. 5349 - 5353
(2021/07/21)
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- Yeast supported gold nanoparticles: an efficient catalyst for the synthesis of commercially important aryl amines
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Candida parapsilosisATCC 7330 supported gold nanoparticles (CpGNP), prepared by a simple and green method can selectively reduce nitroarenes and substituted nitroarenes with different functional groups like halides (-F, -Cl, -Br), olefins, esters and nitriles using sodium borohydride. The product aryl amines which are useful for the preparation of pharmaceuticals, polymers and agrochemicals were obtained in good yields (up to >95%) using CpGNP catalyst under mild conditions. The catalyst showed high recyclability (≥10 cycles) and is a robust free flowing powder, stored and used after eight months without any loss in catalytic activity.
- Krishnan, Saravanan,Patel, Paresh N.,Balasubramanian, Kalpattu K.,Chadha, Anju
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supporting information
p. 1915 - 1923
(2021/02/06)
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- Rhodium-terpyridine Catalyzed Transfer Hydrogenation of Aromatic Nitro Compounds in Water
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A rhodium terpyridine complex catalyzed transfer hydrogenation of nitroarenes to anilines with i-PrOH as hydrogen source and water as solvent has been developed. The catalytic system can work at a substrate/catalyst (S/C) ratio of 2000, with a turnover frequency (TOF) up to 3360 h?1, which represents one of the most active catalytic transfer hydrogenation systems for nitroarene reduction. The catalytic system is operationally simple and the protocol could be scaled up to 20 gram scale. The water-soluble catalyst bearing a carboxyl group could be recycled 15 times without significant loss of activity.
- Liu, Yuxuan,Miao, Wang,Tang, Weijun,Xue, Dong,Xiao, Jianliang,Wang, Chao,Li, Changzhi
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supporting information
p. 1725 - 1729
(2021/06/01)
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- Modified mesoporous y zeolite catalyzed nitration of azobenzene using NO2as the nitro source combined with density functional theory studies
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A modified mesoporous Y zeolite is developed to catalyze high ortho regioselective nitration of azobenzene with NO2 as the nitro source. The mesoporous Y zeolite is modified by the ion exchange method and characterized by various analyses involving FT-IR spectroscopy, and XPS and BET analyses. The ortho/para ratio of mononitration products is improved from 0.70 to 2.39 in the presence of the catalyst. Based on density functional theory (DFT), the active sites of nitration reaction are calculated by combining the electrostatic potential with the average local ionization energy, which are further support the electrophilic substitution mechanism of azobenzene in the catalytic nitration reaction. This journal is
- Chen, Lei,Guo, Chuanzhou,Guo, Jiaming,Peng, Xinhua
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p. 21389 - 21394
(2021/12/04)
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- Catalytic Selective Oxidative Coupling of Secondary N-Alkylanilines: An Approach to Azoxyarene
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Azoxyarenes are among important scaffolds in organic molecules. Direct oxidative coupling of primary anilines provides a concise fashion to construct them. However, whether these scaffolds can be prepared from secondary N-alkylanilines is not well explored. Here, we present a catalytic selective oxidative coupling of secondary N-alkylaniline to afford azoxyarene with tungsten catalyst under mild conditions. In addition, azoxy can be viewed as a bioisostere of alkene and amide. Several "azoxyarene analogues" of the corresponding bioactive alkenes and amides showed comparable promising anticancer activities.
- Ke, Lei,Zhu, Guirong,Qian, Hui,Xiang, Guangya,Chen, Qin,Chen, Zhilong
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supporting information
p. 4008 - 4013
(2019/06/04)
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- Metal-free approach for the ?-proline mediated synthesis of nitrones from nitrosobenzene
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An efficient, and metal-free approach for the ?-proline mediated synthesis of nitrones from nitrosobenzene and benzaldehydes has been established. The reaction undergoes very efficiently at room temperature in methanol as a solvent. The reaction is assumed to involve that the initial formation of azomethine ylide and [2 + 3] cycloaddition of nitrosobenzene, followed by the subsequent retro [2 + 3] cycloaddition could offer the desired nitrone.
- Choi, Minho,Viji, Mayavan,Kim, Donghwan,Lee, Young Hee,Sim, Jaeuk,Kwak, Young-Shin,Lee, Kiho,Lee, Heesoon,Jung, Jae-Kyung
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p. 4182 - 4187
(2018/06/19)
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- Oxidative dimerization of anilines with heterogeneous sulfonic acid catalysts
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We report herein that suitably supported perfluorosulfonic acids can catalyze the oxidative dimerization of anilines using hydrogen peroxide as a clean oxidant. The reaction does not require the use of organic solvents and affords desired azobenzenes and water as products, minimizing the formation of wastes. The metal-free solid catalyst shows remarkable activity and selectivity for the reaction, which occurs under very mild conditions and with broad functional group tolerance.
- Paris, Emanuele,Bigi, Franca,Cauzzi, Daniele,Maggi, Raimondo,Maestri, Giovanni
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p. 382 - 386
(2018/02/07)
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- Highly selective reduction of nitrobenzenes to azoxybenzenes with a copper catalyst
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A convenient protocol for highly selective delivery of azoxybenzenes from reduction of nitrobenzenes was developed by utilizing a copper catalyst. A variety of functional groups and substitution were well tolerated.
- Chen, Zhichao,Qiu, Yatao,Wu, Xiaoxing,Ni, Yong,Shen, Li,Wu, Jun,Jiang, Sheng
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supporting information
p. 1382 - 1384
(2018/03/06)
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- A Highly Selective Amidation of Azoxybenzenes with Sulfonamides via Rhodium(III)-Catalyzed C-H Activation
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A new amidation of azoxybenzenes with sulfonamides catalyzed by a rhodium(III) salt has been developed. This sulfonamidation proceeds efficiently under mild reaction conditions to generate new C-N bonds through C-H bond activation and functionalization, affording the corresponding 2-sulfonamidoazoxybenzenes in good yields with high regioselectivity.
- Li, Hongji,Deng, Hong
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supporting information
p. 2711 - 2720
(2017/06/13)
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- Methoxylation and Direct Hydrogenative Coupling of Chloronitrobenzenes in Continuous Flow
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A novel continuous flow method for the methoxylation of chloronitrobenzenes was developed. The reaction went smoothly and high yields were achieved under the optimized conditions. Furthermore, up to 76% yield of azoxybenzenes were obtained from the corresponding nitrobenzenes in the presence of NaOH in continuous flow. Compared to batch conditions, the reaction time was significantly shortened, and the chemical waste was reduced obviously.
- Shi, Songjie,Wan, Li,Sun, Xiaoning,Zhang, Jiawei,Guo, Kai
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p. 410 - 414
(2017/04/27)
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- Copper-Catalyzed Three-Component Annulations of Alkenes, Nitrosoarenes, and N-Hydroxyallylamines To Form Fused Oxazinane/Isoxazolidine Heterocycles
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One-pot cascade annulations among nitrosoarenes, alkenes, and N-hydroxyallylamines have been achieved with CuCl/O2catalysts, forming fused oxazinane/isoxazolidine heterocycles with excellent diastereoselectivity (d.r. >20:1). To enhance the synthetic utility, we developed a successive cleavage of the two N?O bonds of the resulting heterocycles. A mechanism involving dipolar [3+2] cycloadditions of nitrone intermediates with their tethered alkenes is postulated for formation of these heterocycles.
- Kawade, Rahul Kisan,Liu, Rai-Shung
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p. 2035 - 2039
(2017/02/15)
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- Alkene-directed N-attack chemoselectivity in the gold-catalyzed [2+2+1]-annulations of 1,6-enynes with N-hydroxyanilines
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Kinetically unstable nitrones are generated from gold-catalyzed reactions of 1,6-enynes with N-hydroxyanilines, and subsequently trapped by tethered alkenes to furnish [2+2+1]-annulations. Our experimental data reveal that such nitrones arise from atypical N-attack chemoselectivity that is triggered by tethered alkenes to facilitate the key protodeauration reaction. Kinetically unstable nitrones are generated from gold-catalyzed reactions of 1,6-enynes with N-hydroxyanilines, and subsequently trapped by tethered alkenes to furnish [2+2+1]-annulations. These findings open the door to new ways to access ketone nitrones with good stereoselectivity.
- Huple, Deepak B.,Mokar, Bhanudas D.,Liu, Rai-Shung
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p. 14924 - 14928
(2016/02/05)
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- Monodispersed AuPd nanoalloy: Composition control synthesis and catalytic properties in the oxidative dehydrogenative coupling of aniline
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A series of AuPd@C nanoalloy catalysts with tunable compositions were successfully prepared by a co-reduction method. The use of borane-tert-butylamine complex as reductant and oleylamine as both solvent and reductant was very effective for the preparation of the monodispersed nanoalloy. We evaluated the catalytic activity of these AuPd@C nanoalloys for oxidative dehydrogenative coupling of aniline, which showed better catalytic activity than equal amounts of sole Au@C or Pd@C catalyst. The Au1Pd3@C catalyst exhibited the best performance, indicating that the conversion and selectivity were improved along with the increase of Pd composition. However if the Pd composition was too high in the AuPd alloy, Au1Pd7@C achieved only 81% conversion in this reaction.
- Fu, Fangyu,He, Sen,Yang, Sha,Wang, Chen,Zhang, Xun,Li, Peng,Sheng, Hongting,Zhu, Manzhou
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p. 1532 - 1536
(2015/03/30)
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- Cu-catalyzed aerobic oxidative cyclizations of 3-N-hydroxyamino-1,2-propadienes with alcohols, thiols, and amines to form α-O-, S-, and N-substituted 4-methylquinoline derivatives
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A one-pot, two-step synthesis of α-O-, S-, and Nsubstituted 4-methylquinoline derivatives through Cu-catalyzed aerobic oxidations of N-hydroxyaminoallenes with alcohols, thiols, and amines is described. This reaction sequence involves an initial oxidation of N-hydroxyaminoallenes with NuH (Nu = OH, OR, NHR, and SR) to form 3-substituted 2-en-1-ones, followed by Bronsted acid catalyzed intramolecular cyclizations of the resulting products. Our mechanistic analysis suggests that the reactions proceed through a radical-type mechanism rather than a typical ni-trone-intermediate route. The utility of this new Cu-catalyzed reaction is shown by its applicability to the synthesis of several 2-amino-4-methylquinoline derivatives, which are known to be key precursors to several bioactive molecules.
- Sharma, Pankaj,Liu, Rai-Shung
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supporting information
p. 4590 - 4594
(2015/03/18)
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- Chemistry of unsaturated arenetricarbonylchromium compounds 1. Reaction of (η6-arene)tricarbonylchromium complexes of nitrones with methyl phenylpropiolate
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The reactions of nitrones of the composition (CO)3CrC6H5CH=N+(O-)R (R = Me, Ph, or But) with substituted acetylene were studied. The reactions proceed with high regioselectivity and give 4-
- Zarovkina, N. Yu,Sazonova,Artemov,Fukin
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p. 970 - 975
(2015/02/05)
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- Azo compounds reducing formation and toxicity of amyloid beta aggregation intermediates
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The present invention relates to compounds suitable as modulators of protein misfolding and/or protein aggregation. The compounds are particularly suitable as inhibitors of amyloid aggregate formation and/or modulators of amyloid surface properties, and/or as activators of degradation or reduction of amyloid aggregates.
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- Oxygen activation on metallic centers and oxidizing abilities of such oxygen
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It was shown that metallcontaining peroxides such as XOOOBu-t [X = (t-BuO)2Al, (t-BuO)3Ti] generate molecular oxygen in the electron-excited singlet state (1O2). These ozonides and η2-peroxocomplex Ph3Bi(η2O2) demonstrate high oxidative activity towards some classes of organic substances under mild conditions (20 °C).
- Zaburdaeva, Elena A.,Dodonov, Viktor A.,Stepovik, Larisa P.
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p. 1265 - 1268
(2008/02/04)
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- Oxidative amide synthesis and N-terminal α-amino group ligation of peptides in aqueous medium
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A new method for oxidative synthesis of amides from alkynes and amines in high yields (up to 96%) using [Mn(2,6-Cl2TPP)Cl] 1 as a catalyst and Oxone/H2O2 as an oxidant in aqueous medium has been developed. This method could be used for N-terminal α-amino group ligation of unprotected peptides with aryl, aliphatic, and internal alkynes under mild conditions. Copyright
- Chan, Wing-Kei,Ho, Chi-Ming,Wong, Man-Kin,Che, Chi-Ming
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p. 14796 - 14797
(2008/02/05)
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- The palladium-phenanthroline catalyzed carbonylation of nitroarenes to diarylureas: Effect of chloride and diphenylphosphinic acid
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The application of the palladium-phenanthroline catalytic system to the carbonylation of nitrobenzene in the presence of aniline to afford diphenylurea has been investigated. The reaction is best performed with equimolar amounts of the two reagents. Use of higher concentrations of either aniline or nitrobenzene or an increase in temperature in the range 120-170 °C leads to the formation of higher amounts of azo- and azoxybenzene. The latter were found to contain exclusively the aryl moiety deriving from nitrobenzene, with no inclusion of that derived from aniline. The addition of a small amount of diphenylphosphinic acid doubles the conversion and improves the selectivity in diphenylurea, but the effect is attenuated for larger amounts of acid. Small amounts of chloride, of the order of 10-30 mol% with respect to palladium, improve both rate and selectivity, but only inhibiting effects are detected when chloride is added to the reaction mixture for the carbonylation of 2,4-dinitrotoluene to dimethyl 2,4-toluenedicarbamate. The data obtained and that previously reported in the literature has been analyzed in the context of a unifying mechanism and an explanation for some apparent contradictions has been given.
- Gasperini, Michela,Ragaini, Fabio,Remondini, Chiara,Caselli, Alessandro,Cenini, Sergio
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p. 4517 - 4529
(2007/10/03)
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- 1,2-Eliminations in a novel reductive coupling of nitroarenes to give azoxy arenes by sodium bis(trimethylsilyl)amide
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(Chemical Equation Presented) Symmetric azoxy arenes were successfully prepared in one step from 2 equiv of the corresponding nitroarenes by use of sodium bis-(trimethylsilyl)amide as the deoxygenating agents in THF at 150°C in a sealed tube.
- Jih, Ru Hwu,Das, Asish R.,Chia, Wei Yang,Huang, Jiann-Jyh,Hsu, Ming-Hua
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p. 3211 - 3214
(2007/10/03)
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- Direct amino acid-catalyzed asymmetric desymmetrization of meso-compounds: Tandem aminoxylation/O-N bond heterolysis reactions
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(Chemical Equation Presented) A practical organocatalytic process for the synthesis of optically active, highly substituted α-hydroxy-ketones was achieved through asymmetric desymmetrization (ADS) of prochiral ketones. The ADS and O-N bond reduction reaction of prochiral ketone with nitrosobenzene in the presence of a catalytic amount of chiral amine or amino acid produced the tandem ADS/O-N bond reduced products as single diastereomers with good yields and excellent enantiomeric excesses.
- Ramachary, Dhevalapally B.,Barbas III, Carlos F.
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p. 1577 - 1580
(2007/10/03)
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- Aqueous biphasic oxidation: A water-soluble polyoxometalate catalyst for selective oxidation of various functional groups with hydrogen peroxide
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A "sandwich" type polyoxometalate, Na12[(WZn 3(H2O)2][(ZnW9O34) 2], was used as an oxidation catalyst in aqueous biphasic reaction media to effect oxidation of alcohols, diols, pyridine derivatives, amines and aniline derivatives with hydrogen peroxide. The catalyst was shown by 183W NMR to be stable in aqueous solutions in the presence of H 2O2 and showed only minimal non-productive decomposition of the oxidant. Secondary alcohols were selectively oxidized to ketones, while primary alcohols tended to be oxidized to the corresponding carboxylic acids, although secondary alcohols were selectively oxidized in the presence of primary alcohols. Vicinal diols yielded carbon-carbon bond cleavage products in very high yields. Pyridine derivatives were oxidized to the respective TV-oxides, but strongly electron-withdrawing moieties inhibited the oxidation reaction. Primary amines were oxidized to the oximes, but significantly hydrolyzed in situ. Aniline derivatives were oxidized to the corresponding azoxy or nitro products depending on the substitution pattern in the aromatic ring. Catalyst recovery and recycle was demonstrated.
- Sloboda-Rozner, Dorit,Witte, Peter,Alsters, Paul L.,Neumann, Ronny
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p. 339 - 345
(2007/10/03)
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- Kinetics and mechanism of base-catalysed degradations of substituted aryl-N-hydroxycarbamates, their N-methyl and N-phenyl analogues
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The kinetics and mechanism of the degradation reactions of substituted phenyl N-hydroxycarbamates and their N-methyl and N-phenyl analogues have been studied at pseudo-first-order reaction conditions in aqueous buffers and sodium hydroxide solutions at 20°C and 60°C and at I = 1 mol·1 -1. The dependence of log kobs on pH for phenyl N-hydroxycarbamates at pH 13 is linear with the unit slope; at pH 10-12 log kobs is pH independent. The Bronsted coefficient βlg is about -1 (pH 7-13) and -1.53 (pH > 13) indicating that the degradation reaction of phenyl N-hydroxycarbamates follows an ElcB mechanism giving the corresponding phenol/phenolate and HO-N=C=O. The latter species undergoes further decomposition to give carbonate, nitrogen and ammonia as final products. In contrast to the phenyl N-hydroxycarbamates the N-methyl derivatives at pH 7-9 undergo degradation to the corresponding phenol/phenolate, carbonate and methylamine via a concerted mechanism (βlg is about - 0.75). The only exception is 4-nitrophenyl N-hydroxy-N-methylcarbamate in which the predominant break down pathway proceeds via the Smiles rearrangement to give sodium N-methyl-(4-nitrophenoxy)carbamate. At pH > 9 the reaction of N-hydroxy-N-methylcarbamates is kinetically complex: the dependence of absorbance on time is not exponential and it proceeds as a consecutive two-step reaction. N-Hydroxy-N-phenylcarbamate under the same conditions undergoes degradation to phenol, carbonate, aniline and azoxybenzene.
- Beier, Petr,Mindl, Jaromir,Sterba, Vojeslav,Hanusek, Jiri
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p. 562 - 569
(2007/10/03)
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- Towards the synthesis of azoacetylenes
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The synthesis of azoacetylenes (=dialkynyldiazenes) 1 and 2 has been investigated. They represent a still elusive class of chromophores with potentially very interesting applications as novel bistable photochemical molecular switches or as antitumor agents (Fig. 1). Our synthetic efforts have led us alongside three different approaches (Scheme 1). In a first route, it was envisioned to generate the azo (=diazene) bond by photolysis of N,N′-dialkynylated 1,3,4-thiadiazolidine-2,5-diones that are themselves challenging targets (Scheme 2). Attempts are described to obtain the latter by alkynylation of the parent heterocycle with substituted alkynyliodonium salts. In a conceptually similar approach, the no-less-challenging dialkynylated 9,10-dihydro-9,10-diazanoanthracene (29) was to be generated by alkynylation of the unsubstituted hydrazine 28 (Scheme 6). In a second route, the generation of the N=N bond from Br-substituted divinylidenehydrazines (ketene-azines) 35 was attempted in a synthetic scheme involving an aza-Wittig reaction between azinobis(phosphorane) 36 and (triisopropylsilyl)ketene 37 (Scheme 7). Finally, a third approach, based on the formation of the central azo bond as the key step, was explored. This route involved the extrapolation of a newly discovered condensation reaction of N,N-disilylated anilines with nitroso compounds (Scheme 11, and Tables 1 and 2) to the transformation of N,N-disilylated ynamine 55 and nitroso-alkyne 54 (Scheme 13).
- Denonne, Frederic,Seiler, Paul,Diederich, Francois
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p. 3096 - 3117
(2007/10/03)
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- Mechanism of formation of hydrogen trioxide (HOOOH) in the ozonation of 1,2-diphenylhydrazine and 1,2-dimethylhydrazine: An experimental and theoretical investigation
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Low-temperature (-78 °C) ozonation of 1,2- diphenylhydrazine in various oxygen bases as solvents (acetone-d6, methyl acetate, tert-butyl methyl ether) produced hydrogen trioxide (HOOOH), 1,2-diphenyldiazene, 1,2-diphenyldiazene-N-oxide, and hydrogen peroxide. Ozonation of 1,2-dimethylhydrazine produced besides HOOOH, 1,2-dimethyldiazene, 1,2-dimethyldiazene-N-oxide and hydrogen peroxide, also formic acid and nitromethane. Kinetic and activation parameters for the decomposition of the HOOOH produced in this way, and identified by 1H, 2H, and 17O NMR spectroscopy, are in agreement with our previous proposal that water participates in this reaction as a bifunctional catalyst in a polar decomposition process to produce water and singlet oxygen (O2, 1Δg). The possibility that hydrogen peroxide is, besides water, also involved in the decomposition of hydrogen trioxide is also considered. The half-life of HOOOH at room temperature (20 °C) is 16 ± 1 min in all solvents investigated. Using a variety of DFT methods (restricted, broken-symmetry unrestricted, self-interaction corrected) in connection with the B3LYP functional, a stepwise mechanism involving the hydrotrioxyl (HOOO.) radical is proposed for the ozonation of hydrazines (RNHNHR, R = H, Ph, Me) that involves the abstraction of the N-hydrogen atom by ozone to form a radical pair, RNNHR..OOOH. The hydrotrioxyl radical can then either abstract the remaining N(H) hydrogen atom from the RNNHR. radical to form the corresponding diazene (RN=NR), or recombines with RNNHR. in a solvent cage to form the hydrotrioxide, RN(OOOH)NHR. The decomposition of these very labile hydrotrioxides involves the homolytic scission of the RO-OOH bond with subsequent in cage formation of the diazene-N-oxide and hydrogen peroxide. Although 1,2-diphenyldiazene is unreactive toward ozone under conditions investigated, 1,2-dimethyldiazene reacts with relative ease to yield 1,2-dimethyldiazene-N-oxide and singlet oxygen (O2, 1Δg). The subsequent reaction sequence between these two components to yield nitromethane as the final product is discussed. The formation of formic acid and nitromethane in the ozonolysis of 1,2-dimethylhydrazine is explained as being due to the abstraction of a methyl H atom of the CH3NNHCH3. radical by HOOO . in the solvent cage. The possible mechanism of the reaction of the initially formed formaldehyde methylhydrazone (and HOOOH) with ozone/oxygen mixtures to produce formic acid and nitromethane is also discussed.
- Plesnicar, Bozo,Tuttle, Tell,Cerkovnik, Janez,Koller, Joze,Cremer, Dieter
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p. 11553 - 11564
(2007/10/03)
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- Reactions of carbon dioxide radical anion with substituted benzenes
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We report mechanistic studies on the reactivity of CO2·- radicals towards substituted benzenes, XPh, with X = NO2, COOH, COH, CH3, H, Cl and HO. Vacuum ultraviolet (VUV, 172 nm) irradiation of aqueous solutions containing formate was used as a method of CO2·- radical generation for the study of the reaction products, which were determined by gas chromatography-mass spectrometry and high-performance liquid chromatography. The nature of some of the reaction intermediates was studied by laser flash photolysis of aqueous solutions of peroxodisulfate in the presence of formate. The observed products and intermediates of reaction are discussed and rationalized by a dual reactivity of the CO2·- radical anion with substituted benzenes: a one-electron reduction and radical addition to the aromatic ring. For substituted benzenes with X = NO2, COOH and COH, the observed products support an electron transfer from CO2·- to the substrates as the primary reaction channel, while the reactions with toluene follow the channel of radical addition. Benzene and chlorobenzene react with CO2·- by both routes, electron transfer and radical addition. Our experimental results indicate that H abstraction by the CO2·- radical is negligible under the chosen experimental conditions. Copyright
- Rosso, Janina A.,Bertolotti, Sonia G.,Braun, Andre M.,Martire, Daniel O.,Gonzalez, Monica C.
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p. 300 - 309
(2007/10/03)
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- Reduction of nitroarenes with isopropanol and potassium hydroxide over metal oxide catalysts
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Reduction of aromatic nitrocompounds have been carried out in presence of isopropanol and KOH over some metal oxide catalysts, viz., SnO2, La2O3-SnO2 and La2O3. Reduction of p-nitrobenzophenone has resulted in the chemoselective formation of p-aminobenzophenone. It is proposed that reduction of nitroarenes proceed via a mechanism similar to Meerwin -Pondroff- Verly (M-P-V) reduction of ketones.
- Jyothi,Rao,Sugunan
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p. 1041 - 1043
(2007/10/03)
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- Promotion of the [PPN][Rh(CO)4]-catalysed carbonylation of nitrobenzene by 2-hydroxypyridine and related molecules: An apparent bifunctional activation
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2-Hydroxypyridine and related molecules have a large activating effect on the previously reported [PPN][Rh(CO)4]-based catalytic system for the reductive carbonylation of nitrobenzene to methyl phenylcarbamate (PPN+=(PPh3)2N+). The effect is not due to the known 2-hydroxypyridine-2-pyridone tautomeric equilibrium, since 4-hydroxypyridine, for which the same tautomeric equilibrium exists, completely inhibits the reaction. A promoting effect of 2-hydroxypyridine is also observed in the reactions of a previously isolated metallacyclic complex, [PPN][Rh(CO)2ON(Ar)C(O)O], believed to be an intermediate in the catalytic reactions. However, the dependence of the rate of the catalytic reactions on the aniline concentration indicates that the effect found for the stoichiometric reaction cannot be the one that is relevant for the acceleration of the catalytic reactions. Thus, two different effects are present, both of which appear to be due to the proximal positions of a basic and an acidic site in the promoter molecules.
- Ragaini, Fabio,Gallo, Emma,Cenini, Sergio
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p. 109 - 118
(2007/10/03)
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- Copper-catalyzed amination of alkenes and ketones by phenylhydroxylamine
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The catalytic activity of a number of copper complexes and salts toward allylic amination of alkenes using phenylhydroxylamine as the nitrogen fragment donor has been investigated. The best catalyst is CuCl2·2H2O, which produces moderate yields of allylamines with high regioselectivity resulting from double bond transposition. A mechanism similar to that for the molybdenum and the FePc systems is proposed. The first step in the catalytic cycle is the formation of nitrosobenzene from the oxidation of phenylhydroxylamine by Cu(II). The next step is an ene reaction of the alkene with PhNO to produce an allylhydroxylamine, which is then reduced to the allylamine product by Cu(I), thus regenerating Cu(II). The same system can also transfer the nitrogen fragment to the α-carbon of cyclic ketones; this is accompanied by dehydrogenation in some cases to produce α-aminated, α,β-unsaturated ketones.
- Ho,Lau
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p. 859 - 863
(2007/10/03)
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- O-Alkylation of Cupferron: Aiming at the Design and Synthesis of Controlled Nitric Oxide Releasing Agents
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O-Alkylation of N-nitroso-N-phenylhydroxylamine ammonium salt (cupferron) was studied for the synthesis of novel nitric oxide (NO) releasing agents. The alkylation occurred regioselectively at the terminal oxygen, leading to a single product N-(alkyloxy)-N′-phenyldiimide N′-oxide as indicated by NMR and X-ray analysis. The O-alkyl derivatives exhibited significantly improved stability compared to their parent compound, cupferron. It was demonstrated that the cupferron O-alkyl derivatives could function as photoreleasing NO donor compounds. N-(N″-acetylphenylalanylmethylenyloxy)-N′-phenyldiimide N′-oxide), which linked the cupferron portion with an amino acid via an acetal moiety, was synthesized as an model NO prodrug where controlled NO release would occur either by increasing pH or by a protease-catalyzed hydrolysis.
- Hou, Yongchun,Xie, Wenhua,Janczuk, Adam J.,Wang, Peng George
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p. 4333 - 4337
(2007/10/03)
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- Influence of various P/N and P/P ligands on the palladium-catalysed reductive carbonylation of nitrobenzene
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A series of bidentate phosphorus-nitrogen ligands was synthesised for the palladium-catalysed reductive carbonylation of nitrobenzene in order to combine the favourable influence of the phosphorus atom on the stability of the catalyst complex with the stimulating effect of the nitrogen atom on the catalytic activity. The nitrogen atom of the P/N ligand was either incorporated in an imine function, yielding the JV-(2′-diphenylphosphinobenzylidene)-R-amine ligands (R = phenyl, 4-chlorophenyl, 2,4-dimethoxyphenyl, 2,4-dimethylphenyl, tert-butyl), or in a heteroaromatic ring system which gave 2-(2′-(diphenylphosphino)ethyl)pyridine and 8-(diphenylphosphino)quinoline. Complexes of the type Pd(ligand)2(BF4)2 were prepared for these ligands. Additionally, a series of bidentate phosphorus ligands was tested: dppm, dppe, dppp, dppb, dppf, 1,2-bis(diphenylphosphino)benzene, 1,8-bis(diphenylphosphino)naphthalene, bis(2-diphenylphosphinophenyl)ether, and 9,9-dimethyl-4,6-bis(diphenylphosphino)xanthene. The P/N ligands containing the imine function did not yield any conversion of the nitrobenzene in combination with Pd. On the use of the second type of P/N ligand, moderately active palladium catalysts were obtained. This different behaviour is ascribed to the relatively low π *-level of the imine-containing ligands. Oxidation of the phosphorus donor atom by the nitro substrate inactivated the catalysts derived from the P/N ligands as well as from a series of P/P ligands. For the bidentate phosphorus ligands the bite angle and flexibility of the ligand turned out to be of crucial influence due to the different geometries required for the Pd(II) and Pd(0) intermediates of the catalytic cycle.
- Wehman, Petra,Van Donge, Hans M.A.,Hagos, Alay,Kamer, Paul C.J.,Van Leeuwen, Piet W.N.M.
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p. 183 - 193
(2007/10/03)
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- A new catalytic method for the selective oxidation of aniline to nitrosobenzene over titanium silicate molecular sieves, TS-1, using H2O2 as oxidant
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The oxidation of aniline to nitrosobenzene with a selectivity > 73% has been achieved using titanium silicate molecular sieves, TS-1 as catalyst and aqueous H2O2 as oxidant at 273 K in a batch reaction.
- Selvam,Ramaswamy
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p. 1215 - 1216
(2007/10/03)
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- Sulfonic peracids - III. Heteroatom oxidation and chemoselectivity
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We have investigated the p-toluenesulfonic peracid (2) generated in situ in the oxidation of different types of compounds containing nitrogen and/or sulfur. The sulfonic peracid 2 shows a remarkable chemoselectivity characterized by a preferred oxidation of sulfides to the sulfones in the presence of amines or olefins and a strong dependence on the nature of the amine in the competitive oxidation of olefins and amines.
- Kluge,Schulz,Liebsch
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p. 5773 - 5782
(2007/10/03)
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- Kinetics and Mechanism of Oxidation of Anilines by Hydrogen Peroxide As Catalyzed by Methylrhenium Trioxide
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The oxidation of anilines by hydrogen peroxide in methanol is catalyzed by methylrhenium trioxide, CH3ReO3.The major product of the oxidation of aniline at room temperature is nitrosobenzene.For 4-substituted N,N-dimethylanilines, the N-oxide is the only product.The rate constants for the oxidation of 4-substituted N,N-dimethylanilines follow a linear Hammett relationship with ρ = -1.19.The rate constants for the reaction between CH3Re(O)2(O2), referred to as A, and 4-XC6H4-NMe2 are as follows: 4-Me, 24.5; 4-H, 18.4; 4-F, 12.7; 4-Br, 8.7; and 4-NO2, 1.0 L mol-1 s-1.This shows that electron-withdrawing substituents inhibit the reaction.The corresponding rate constant for the oxidation of aniline is 2.04 +/- 0.11 L mol-1 s-1, whereas it is 178 +/- 11 L mol-1 s-1 for the oxidation of N-phenylhydroxylamine to nitrosobenzene.A mechanism has been assigned on the basis of the kinetics and product yields.The data are consistent with the attack of the nucleophilic nitrogen atom on one of the peroxidic oxygen atom of A.The kinetics of the reaction of CH3ReO3 and hydrogen peroxide in methanol were also investigated.The formation of the 1:1 peroxide compound A is characterized by an equilibrium constant K1 = 261 +/- 6 L mol-1.The equilibration occurs rapidly: k1 = 1150 +/- 60 L mol-1 s-1 and k-1 = 4.4 +/- 0.4 s-1 at 25.0 deg C.The bisperoxide compound, CH3Re(O)(O2)2(H2O), B, forms more slowly.The rate constant is k2 = 308 +/- 16 L mol-1 s-1, and the equilibrium constant is K2 = 814 +/- 14 L mol-1 at 25.0 deg C in methanol.B reacts with the anilines, but much more slowly than A.
- Zhu, Zuolin,Espenson, James H.
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p. 1326 - 1332
(2007/10/02)
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- ON THE MECHANISM OF THE REACTION OF NITROSOBENZENES WITH BENZENETHIOL: THE INTERMEDIACY OF AMINOXYLS AND THEIR DEOXYGENATION
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The reaction of benzenethiol with several substituted nitrosobenzenes carried out inside the cavity of an EPR spectrometer evidences the formation of adducts through the detection of the corresponding thionitroxides.The macroscale reaction of benzenethiol with nitrosobenzene confirmed the formation of the adduct and clarified the nature of the intermediates.The formation of azoxybenzene, aniline and nitrobenzene shows that an electron-transfer process between nitrosobenzene and benzenethiol is in competition with nucleophylic addition of the latter to the former compound.The identification of S-phenylbenzenethiosulphinate as well as the isolation of compound 9, bearing a sulphinyl group on a benzene ring, implies the formation of a sulphinyl radical, which is considered to be responsible for the formation of the sulphinylamide.The formation of the sulpheneamide, the main reaction product, is attributed to the interaction of thiyl radicals with the intermediate thionitroxides.The crystal structure of S-methyl-S-phenyl-N-(o-sulphonylphenyl)benzenesulphilimine, the unexpected product of the methylation of compound 9, is also described.
- Alberti, Angelo,Benaglia, Massimo,Carloni, Patricia,Greci, Lucedio,Stipa, Pierluigi,et al.
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p. 555 - 562
(2007/10/02)
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- Vicarious nucleophilic substitution of nitrobenzenes : Application of the reaction to 2-alkylnitrobenzenes
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Vicarious nucleophilic substitution (VNS) by dichloroacetate and other reagents has been applied in good yield to various ortho-substituted nitrobenzenes including 2-nitrotoluene and 2-nitro ethylbenzene. For alkyl nitrobenzenes, ease of VNS increased para ortho meta and methyl ethyl iso-propyl. Formation of chlorine-free products upon VNS by methyl dichloro- acetate suggests the involvement of radical anions.
- DeBoos,Milner
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p. 965 - 976
(2007/10/02)
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- Iron-catalyzed allylic amination
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The transition-metal-catalyzed allylic amination of alkenes is studied. A screening of different transition-metal complexes reveals that iron complexes, especially iron phthalocyanin, have the best catalytic properties, using phenylhydroxylamine as the nitrogen-fragment donor. The iron phthalocyanin-catalyzed reaction has been studied for a variety of alkenes and the best yields are obtained for alkenes substituted with aromatic groups. The scope of this reaction is discussed.
- Johannsen,Jorgensen
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p. 214 - 216
(2007/10/02)
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- Electrochemically Induced Chain Reactions: The Electrochemical Behavior of Nitrosobenzene in the Presence of Proton Donors in Tetrahydrofuran
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The electrochemical reduction of nitrosobenzene in tetrahydrofuran with tetrabutylammonium hexafluorophosphate as the supporting electrolyte and in the presence of fluorene or indene at room temperature gives a mixture of an anil (1 or 3), a nitrone (2 or 4), and azoxybenzene and requires only a catalytic amount of electricity.Lowering the temperature and/or increasing the proportion of proton donor favors the formation of the anil at the expense of the nitrone and azoxybenzene: a 97percent yield of anil 1 was obtained from an electrolysis carried out at -30 deg C using 5 equiv of fluorene.The possible steps of the chain reactions involved are discussed on the basis of electrochemical and chemical data and digital simulation.With phenylacetylene as the proton donor, there is no reaction between nitrosobenzene and phenylacetylene and azoxybenzene is the main product formed.
- Mugnier, Yves,Gard, Jean-Christophe,Huang, Youqin,Couture, Yvon,Lasia, Andrzej,Lessard, Jean
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p. 5329 - 5334
(2007/10/02)
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- Amination of Nitrobenzene via Nucleophilic Aromatic Substitution for Hydrogen: Direct Formation of Aromatic Amide Bonds
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The first example of the direct formation of aromatic amide bonds via nucleophilic aromatic substitution for hydrogen is described.Thus, the reaction of benzamide, tetramethylammonium hydroxide dihydrate, and nitrobenzene under anaerobic conditions generates N-(4-nitrophenyl)benzamide (1) (98percent) and azoxybenzene (30percent) in isolated yields.In addition, other substituted benzamides and aliphatic amides are shown to function as nucleophiles in this reaction.A mechanism that is consistent with the simultaneous formation of anilide products and azoxybenzene which requires the oxidation of ?-complex intermediates by nitrobenzene initially generating nitrobenzene radical anions is proposed.By contrast, when the reaction is run under aerobic conditions, the formation of azoxybenzene is completely inhibited due to the trapping of nitroarene radicals by O2.The ability to prepare 1 in high yield and regioselectivity affords a novel route for the direct amination of nitrobenzene that does not require halogenated intermediates or auxiliary leaving groups.Accordingly, treatment of 1 with methanolic ammonia results in the aminolysis of the amide bond producing 4-nitroaniline and regenerates benzamide.
- Stern, Michael K.,Cheng, Brian K.
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p. 6883 - 6888
(2007/10/02)
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- ELECTRON TRANSFER REACTIONS. 1. UNUSUAL BEHAVIOUR OF TRIPHENYLCHLOROMETHANE IN NITROBENZENE
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The reaction of triphenylchloromethane 1 with nitrobenzene 2 under both thermic and ultrasonic activation has been investigated. The obtained products indicate as possible an electron transfer mechanism in which triphenylchloromethane is donor and nitrobenzene is acceptor. This type of electron transfer from triphenylchloromethane has not been observed until now.
- Iancu, Adrian I.,Oniciu, Daniela C.,Plugariu, Carmela,Bartha, Emerich,Vinatoru, Mircea,Badea, Florin
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p. 1275 - 1278
(2007/10/03)
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- REACTION OF 3,5-DI-t-BUTYLNITROSOBENZENE WITH ALKOXIDES AND CARBANIONS
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The reaction of 3,5-di-t-butylnitrosobenzene with alkoxides (MeOM, EtOM, i-PrOM and t-BuOM, where the metal M is either sodium or potassium) has been studied in different solvents (the corresponding alcohols, DMF, DMSO, N-methyl pyrrolidone, benzene and toluene), either in presence or in absence of camphor or a camphor derivative substituted in position 3 with a group RCO (R=H, OEt, COOEt). The reaction was followed by ESR-spectrometry, in order to detect the intermediate nitroxide radicals. The carbonyl compound is involved with certainty in the formation of the observed radicals in the case of 3-formylcamphor, 8, and probably in the reaction performed in the presence of the unsubstituted camphor. In the absence of the carbonyl compounds, as well as in their presence, depending on the system base-solvent used in the reaction, a process similar to that described by Aurich et al. was observed, leading to the anion radical of the nitrosoarene. The ESR spectra of the anion radical change in time, indicating the formation of another nitroxide radical. The results are discussed in relation with the reports of Aurich group and our own experience in this field.
- Badea, Florin,Balaban, Alexandru T.,Costea, Ion,Iordache, Florin,Meghea, Aurelia,Oniciu, Daniela Carmen
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p. 157 - 170
(2007/10/03)
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- Metathesis and reduction reactions of nitroso compounds with metal carbenes and metal carbonyls
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Reaction of nitroso compounds with metal-carbene complexes and metal carbonyls has been investigated.These reactions lead to reduction of the nitroso compounds, primarily to the corresponding azo- and azoxy compounds.Metal-nitrene complexes have been proposed as intermediates in these reactions.These intermediates couple rapidly with the unreacted nitroso compound, or enter into nitrene-like reactions with external or internal trapping agents.Reaction of metal carbonyls with nitrosoarenes and photolysis has been found to be an effective method for the reduction of nitrosoarenes to azoxyarenes, with few problems resulting from overreduction to amines or azo compounds.
- Herndon, James W.,McMullen, Leonard A.
-
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- CARBONYLATION OF NITROSOBENZENES TO CARBAMATE ESTERS CATALYZED BY PALLADIUM AND CUPRIC ACETATES UNDER AMBIENT CONDITIONS
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Palladium acetate and cupric acetate are effective catalysts for the reaction of nitrosobenzenes with carbon monoxide and alcohol at room temperature and one atmosphere.
- Alper, Howard,Vasapollo, Giuseppe
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p. 6411 - 6412
(2007/10/02)
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- Mechanism of Carboxylic Acid-Catalyzed Reduction of Substituted Nitrosobenzenes by 1-Benzyl-3,5-bis(1-pyrrolidinylcarbonyl)-1,4-dihydropyridine in Acetonitrile
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Mechanism of carboxylic acid-catalyzed reduction of substituted nitrosobenzenes by 1-benzyl-3,5-bis(1-pyrrolidinylcarbonyl)-1,4-dihydropyridine has been studied in acetonitrile at 25 deg C.The major product was hydroxylamine when the dihydropyridine was used in excess over nitrosobenzene, while that was azoxybenzene in the reverse case.The observed second-order rate constant kR2 are dependent on acid concentration in a first-order manner with the acid-catalyzed third-order rate constant kRH.The Hammett relationship for kRH for substituted nitrosobenzenes gave a ρ=-0.93.The Broensted plot of log kRH vs. pKa of acids gave a straight line with a slope of -0.34.The deuterium isotope effect for the catalysis by dichloroacetic acid was found to be kRH/kRD=2.80.These results indicate that a general acid catalysis by carboxylic acids plays an important role in the reduction of nitrosobenzene by dihydropyridine in acetonitrile.
- Awano, Hiroshi,Tagaki, Waichiro
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p. 3117 - 3124
(2007/10/02)
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- A NEW SYNTHESIS OF NITRO COMPOUNDS USING DIMETHYLDIOXIRANE
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Dimethyldioxirane oxidizes primary amines to nitro compounds in a facile, mild, high yield process.
- Murray, Robert W.,Jeyaraman, Ramasubbu,Mohan, Lily
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p. 2335 - 2336
(2007/10/02)
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