- Competition between Radical and Nonradical Reactions of Halonitrobenzenes in Alkaline Alcoholic Solutions
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The study of the reactivity of monohalonitrobenzenes in 2-propanol solutions of potassium 2-propoxide has led to the identification of three distinct reaction paths: (a) hydro dehalogenation to nitrobenzene, (b) alkoxy dehalogenation via the SNAr mechanism, and (c) nitro reduction to azoxy and anilino derivatives via nitroso intermediates.With the exception of 2- and 4-fluoronitrobenzene, radical processes c or a are faster than the SNAr reaction.The radical processes proceed via a common intermediate, the radical anion *-, which can undergo unimolecular fragmentation to nitroaryl radical and X- (path a, favored for X = 2-I, 2-Br), or reduction to the dianion 2-, the direct precursor of the nitroso intermediate XC6H4NO (path c).In the presence of oxyen, an effective oxidant of the radical-anion intermediate, the SNAr reaction prevails for the activated ortho and para substrates.Cation-anion interactions are also major consequence in determining the course of reaction.Ion pairing favors nitro reduction, whereas it slows both the SNAr and the hydro dehalogenation reactions.
- Arca, Vittorio,Paradisi, Cristina,Scorrano, Gianfranco
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- Convergent Paired Electrochemical Synthesis of Azoxy and Azo Compounds: An Insight into the Reaction Mechanism
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A convergent paired electrochemical method was developed for the synthesis of azoxy and azo compounds starting from the corresponding nitroarenes. We propose a unique mechanism for electrosynthesis of azoxy and azo compounds. We find that both anodic and cathodic reactions are responsible for the synthesis of these compounds. The synthesis of azoxy and azo derivatives have been successfully performed in an undivided cell, using carbon rod electrodes, by constant current electrolysis at room temperature.
- Sadatnabi, Ali,Mohamadighader, Niloofar,Nematollahi, Davood
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supporting information
p. 6488 - 6493
(2021/08/23)
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- Au@zirconium-phosphonate nanoparticles as an effective catalytic system for the chemoselective and switchable reduction of nitroarenes
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In the present paper, a novel inorganic-organic layered material, a zirconium phosphate aminoethyl phosphonate, ZP(AEP), bearing aminoethyl groups on the layer surface, was used to immobilize AuNPs by a two-step procedure. The gold-based catalyst, Au1@ZP(AEP), containing 1 wt% Au, was characterized in terms of physico-chemical properties and TEM analysis revealed that the AuNPs have a spherical shape and an average size of 7.8 (±2.4) nm. Au1@ZP(AEP) proved its high efficiency for the chemoselective reduction of nitroarenes under mild conditions. Both batch and flow condition protocols have been defined. The catalytic system has been proven to be able to easily switch chemoselectivity allowing the control of the reduction of a series of nitroaromatics towards their corresponding azoxyarenes (2a-k) or anilines (2a-l) in 96% EtOH or abs EtOH, respectively, by using NaBH4 as a reducing agent, in good to excellent yields. Recovery and reuse of the catalytic system has been investigated proving the benefits of the flow approach.
- Ferlin, Francesco,Cappelletti, Matteo,Vivani, Riccardo,Pica, Monica,Piermatti, Oriana,Vaccaro, Luigi
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supporting information
p. 614 - 626
(2019/02/13)
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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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- Aromatic amine oxidation process for preparing aromatic liquid discharge method
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The invention relates to a preparation method for aromatic-azoxybenzene by oxidizing aromatic amine. According to the method, air or oxygen is used as an oxygen source, and aromatic amine is oxidized to be aromatic-azoxybenzene under the effect of metal oxide catalyst. The method has the advantage of high product yield and is easy to separate the catalyst.
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Paragraph 0014; 0015; 0016; 0017; 0018; 0019-0023; 0025
(2017/08/26)
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- Ultrasound-accelerated selective oxidation of primary aromatic amines to azoxy derivatives with trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane catalyzed by Preyssler acid-mediated nano-TiO2
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Preyssler-type heteropolyacid supported on TiO2 nanoparticles has been explored as an efficient catalyst in selective oxidation of primary aromatic amines to azoxy derivatives using trans-3,5-dihydroperoxy-3,5-dimethyl- 1,2-dioxolane as oxidant. The reactions proceeded smoothly under mild and green ultrasound-accelerated conditions to afford the products in high yields. The catalyst recovered from the reaction mixture exhibits long-term stability with no significant drop in its catalytic activity. Graphical abstract: [Figure not available: see fulltext.].
- Azarifar, Davood,Khatami, Seyed-Mola,Najminejad, Zohreh
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p. 587 - 592
(2014/04/03)
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- Reduction of nitroarenes to azoxybenzenes by NaOH-PEG 400
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The reduction of nitroarenes to azoxybenzenes by NaOH-PEG 400 in benzene is described. The protocol is facile, economical, and effective.
- Liu, Yufang,Liu, Bo,Guo, Ailing,Dong, Zhenming,Jin, Shuo,Lu, Yun
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experimental part
p. 2201 - 2206
(2012/06/16)
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- Reduction of nitroarenes to azoxybenzenes by potassium borohydride in water
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The synthesis of the azoxybenzenes by the reduction of nitroarenes with reducing agent potassium borohydride in water was reported for the first time. PEG-400 was used as a phase transfer catalyst and could effectively catalyze the reduction. The electronic effects of substituent groups play an important role in determining the reduction efficiencies. Electron-withdrawing substituents promote the formation of the azoxybenzene products, while electron-releasing groups retard the reductions to various degrees depending on the extent of their electron-donating ability.
- Liu, Yufang,Liu, Bo,Guo, Ailing,Dong, Zhenming,Jin, Shuo,Lu, Yun
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experimental part
p. 3563 - 3568
(2011/06/26)
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- Switchable selectivity during oxidation of anilines in a ball mill
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A solvent-free method for the direct oxidation of anilines to the corresponding azo and azoxy homocoupling products by using a planetary ball mill was developed. Various oxidants and grinding auxiliaries were tested and a variety of substituted anilines were investigated. It was possible to form chemoselectively either azo, azoxy, or the nitro compounds from reaction of aromatic anilines. The selectivity of the solvent-free reaction is switchable by applying a combination of oxidant and grinding auxiliary. Furthermore, a comparison with other methods of energy input (microwave, classical heating, and ultrasound) highlighted the advantages of the ball mill approach and its high energy efficiency. Grinding reactions: Highly efficient oxidative homocoupling of aromatic amines was performed under solvent-free conditions in a planetary ball mill (see scheme). The choice of solid oxidants and grinding auxiliaries allowed selective generation of the oxidized products. Other methods of energy input are compared with respect to reaction time and energy consumption.
- Thorwirth, Rico,Bernhardt, Franziska,Stolle, Achim,Ondruschka, Bernd,Asghari, Jila
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supporting information; experimental part
p. 13236 - 13242
(2011/02/21)
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- Oxygen as moderator in the zinc-mediated reduction of aromatic nitro to azoxy compounds
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A simple and useful protocol for the reduction of nitro arenes to their corresponding azoxy derivatives by employing zinc and NH4Cl in a mixture of [bmim][BF4] and water is described. The selective reduction of nitro to azoxy is attributed to the hitherto unknown moderating effect of oxygen on zinc metal.
- Khan, Faiz Ahmed,Sudheer
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experimental part
p. 3394 - 3396
(2009/09/05)
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- Reduction of mononitroarenes by hydroxide ion in water catalyzed by β-cyclodextrin: enhanced reactivity of hydroxide ion
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Ordinarily the reducing ability of HO- in water is extremely low as a result of its stabilization by hydration. Reductions by hydroxide ion have only been observed previously in aprotic organic solvents. We find that several mononitroarenes are reduced to azoxyarenes by NaOH in water in the presence of β-cyclodextrin. HO- acts as a one-electron reductant with enhanced reactivity.
- Lu, Yun,Liu, Jiancheng,Diffee, Garry,Liu, Diansheng,Liu, Bo
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p. 4597 - 4599
(2007/10/03)
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- Bi-KOH. An efficient reagent for the coupling of nitroarenes to azo and azoxy compounds
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A simple and inexpensive procedure for the coupling of nitroarenes to azoxy compounds with bismuth and potassium hydroxide in methanol at ambient temperature is achieved. When carried out under microwave irradiation it gives exclusively azo compounds in excellent yields.
- Laskar, Dhrubojyoti Dey,Prajapati, Dipak,Sandhu, Jagir S.
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- Reduction of aromatic azo-,azoxy- and nitro-compounds by ultrasonically activated nickel
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Substituted hydrazobenzenes were obtained in excellent yields from reduction of the corresponding azo- or azoxy- compounds by hydrazine hydrate under the catalysis of ultrasonically activated nickel (UAN). Reduction of nitroarenes by UAN produced azoxyarenes as the major products.
- Wang, Xiaolun,Xu, Minghua,Lian, Hongzhen,Pan, Yi,Shi, Yaozeng
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p. 3031 - 3037
(2007/10/03)
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- Cadmium chloride-zinc catalysed selective reduction of nitro aromatics to azoxy compounds
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Treatment of aromatic nitro compounds with cadmium chloride-metallic zinc combination systems has been shown to display a good reaction selectivity in the formation of symmetrical azoxy compounds in high yields.
- Baruah, Bipul,Boruah, Anima,Prajapati, Dipak,Sandhu, Jagir S.
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p. 351 - 352
(2007/10/03)
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- Bismuth(III) Chloride-Zinc Promoted Selective Reduction of Aromatic Nitro Compounds to Azoxy Compounds
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In the presence of bismuth(III)chloride-metalllic zinc aromatic nitro compounds have been found to be selectively reduced inter and intramolecularly to the corresponding N-oxides at ambient temperature in high yields.
- Borah, Harsha N.,Prajapati, Dipak,Sandhu, Jagir S.,Ghosh, Anil C.
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p. 3167 - 3170
(2007/10/02)
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- Nucleophilic Substitution of Nitrite in Nitrobenzenes, Nitrobiphenyls and Nitronaphthalenes
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Aromatic compounds, accessible only by multistep procedures, can be synthesized easily by nucleophilic substitution of nitrite in nitrobenzenes, nitrobiphenyls, and nitronaphthalines.Thus, meta-substituted phenols 3, 4, and 7 are obtained from 1,3-dinitrobenzene (1) and meta-substituted nitrobenzenes 6, as well as 3,5-disubstituted phenols 10 and 5-substituted resorcinol derivatives 11 from 3,5-disubstituted nitrobenzenes 9.The unsymmetrically substituted nitrobiphenyls 13, 15, 17, 19, 23, 24, and 26 are also available by nitrite exchange from the corresponding easily accessible dinitrobiphenyls 16, 18, 20, 22, and 25.A nitrite exchange with nucleophiles is easily possible in the 1,5-disubstituted naphthalenes 29, 34, while in the case of the 1,8-disubstituted naphthalenes 31, 36 only the chloro derivative 36 undergoes this exchange under much stronger conditions in low yield.
- Effenberger, Franz,Koch, Markus,Streicher, Willi
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p. 163 - 173
(2007/10/02)
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- Studies of the use of elemento-organic compounds of the fifteenth and sixteenth groups in organic synthesis LXXV *. Reduction of some organic compounds by tertiary stibines
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Trialkylstibines can reduce nitroarenes to azoxy compounds, quinone to hydroquinone, and p-toluenesulfonyl chloride to p-toluenesulfinic acid in good yields under mild conditions.Debromination of α-bromophenylacetonitrile or 1,2-dibromo-1-phenylethane by tri-n-butylstibine gives 2,3-diphenylsuccinonitrile or styrene, respectively.
- Huang, Yao-Zeng,Chen, Chen,Zhu, Fanghua,Liao, Yi
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p. 147 - 152
(2007/10/02)
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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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