- Preparation of niobium or tantalum complex and application of niobium or tantalum complex in catalyzing aromatic amine to generate oxidized azobenzene compound
-
The invention provides a preparation method of niobium or tantalum complex and an application of the niobium or tantalum complex in catalyzing aromatic amine to generate an oxidized azobenzene compound. The preparation method of the complex comprises A hydration oxide preparation, @timetime@ niobium oxide or tantalum oxide and strong base in 300 - 800 °C melting calcination 2 - 8h, adding water to dissolve and filter, and then adjusting pH through 4-6, suction filtration and drying. The B complex is prepared by mixing a hydrated oxide with a molar ratio 10-25: 1 with hydrogen peroxide, adding an organic acid and a cationic precursor after clarifying the solution, and evaporating and drying to obtain a niobium complex or a tantalum complex. The molar ratio @timetime@: 1-3. In the method for synthesizing the oxidized azobenzene compound by using niobium or tantalum complex as a catalyst, ethanol is used as a solvent, hydrogen peroxide is used as an oxidant, niobium complex or tantalum complex is used as a catalyst, and the addition amount is ppm.
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Paragraph 0072-0075
(2021/11/03)
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- SO2F2-mediated oxidation of primary and tertiary amines with 30% aqueous H2O2 solution
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A highly efficient and selective oxidation of primary and tertiary amines employing SO2F2/H2O2/base system was described. Anilines were converted to the corresponding azoxybenzenes, while primary benzylamines were transformed into nitriles and secondary benzylamines were rearranged to amides. For tertiary amine substrates quinolines, isoquinolines and pyridines, their oxidation products were the corresponding N-oxides. The reaction conditions are very mild and just involve SO2F2, amines, 30% aqueous H2O2 solution, and inorganic base at room temperature. One unique advantage is that this oxidation system is just composed of inexpensive inorganic compounds without the use of any metal and organic compounds.
- Liao, Xudong,Zhou, Yi,Ai, Chengmei,Ye, Cuijiao,Chen, Guanghui,Yan, Zhaohua,Lin, Sen
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supporting information
(2021/11/01)
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- Preparation of azoxy benzene (by machine translation)
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[A] good workability and safety, cost, and, efficient production of the azoxy benzene azoxy benzene can be produced. [Solution] nitrobenzene ones, having the photocatalytic function with a dye, a reducing agent such as a fluorine resin or a transparent resin material is a mixed solution of 1 mm in diameter are inserted into the tube 4 does not inhibit the reaction, 4 LED lamp 5 emits visible from the outside of the tube moves within the tube 4 is provided with visible light within the tube 4 by a photocatalyst reaction mixed solution so as to obtain azoxy benzene compounds. Figure 2 [drawing] (by machine translation)
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Paragraph 0029; 0036
(2020/05/21)
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- Method for synthesizing oxidized azo compound through selective oxidation of aromatic amine
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The invention discloses a method for synthesizing an oxidized azo compound through selective oxidation of an aromatic amine, wherein an aromatic amine is used as a raw material, hydrogen peroxide is used as an oxidizing agent, a titanium-silicon molecular sieve or a metal modified titanium-silicon molecular sieve is used as a catalyst, and the aromatic amine is subjected to selective catalytic oxidation to prepare the corresponding oxidized azobenzene compound. According to the present invention, the method has advantages of environmental protection, good selectivity, high product yield, easyseparation and recycling of the catalyst, simple instrument required by the reaction, and easy operation.
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-
Paragraph 0027-0051; 0052-0055
(2019/02/13)
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- Nb2O5 supported on mixed oxides catalyzed oxidative and photochemical conversion of anilines to azoxybenzenes
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The synthesis of novel supported niobium oxide catalysts and their application for aniline conversion to azoxybenzenes is described. The catalysts were successfully prepared by thermal decomposition of layered double hydroxides (LDHs), containing M2+ (M = Mg2+ and/or Zn2+) and Al3+ as layer cations, followed by niobium oxide incorporation employing the wetness impregnation method. These catalysts were fully characterized by both experimental techniques and theoretical calculations, and then successfully applied to the selective conversion of anilines into azoxybenzene derivatives, with up to 98% conversion and 92% isolated yield in the presence of violet light. Control experiments and DFT calculations revealed that the catalyst has a dual role in this transformation, acting both as a Lewis acid in the oxidative step and as a photocatalyst in the dimerization of the nitrosobenzene intermediate.
- De Carvalho, Gustavo Senra Gon?alves,Chagas, Luciano Honorato,Fonseca, Carla Grijó,De Castro, Pedro P?ssa,Sant'Ana, Ant?nio Carlos,Leit?o, Alexandre Amaral,Amarante, Giovanni Wilson
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supporting information
p. 5863 - 5871
(2019/04/17)
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- Low-temperature catalytic oxidation of aniline to azoxybenzene over an Ag/Fe2O3 nanoparticle catalyst using H2O2 as an oxidant
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An in situ modified hydrothermal synthesis of Ag/Fe2O3 nanoparticles (NPs) and studies of their catalytic activity as a simple, eco-friendly and recyclable catalyst for one-pot conversion of aniline to azoxybenzene were performed. The as-synthesized nanostructured material was characterised by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), SEM-mapping, temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherms (BET), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), ultraviolet-visible spectroscopy (UV-vis) and vibrating sample magnetometer spectroscopy (VSM). The most active and recyclable catalyst with 2-5 nm diameters of the metallic Ag particles supported on 10-50 nm Fe2O3 nanoparticles was formed with a silver loading of 1.8 wt%. A high turnover number of ~592 was achieved with 92% conversion of aniline and 94% selectivity towards the target product azoxybenzene under atmospheric conditions. The effects of various reaction parameters including the reaction time, temperature and substrate to H2O2 molar ratio were screened and studied in detail. The results reveal the role of a synergistic effect between the surface Ag nanoparticles and Fe2O3 nanospheres for high catalytic activity.
- Paul, Bappi,Sharma, Sachin K.,Adak, Shubhadeep,Khatun, Rubina,Singh, Gurmeet,Das, Dipak,Joshi, Vedant,Bhandari, Sahil,Dhar, Siddhartha Sankar,Bal, Rajaram
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p. 8911 - 8918
(2019/06/18)
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- Modulating the catalytic behavior of non-noble metal nanoparticles by inter-particle interaction for chemoselective hydrogenation of nitroarenes into corresponding azoxy or azo compounds
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Aromatic azoxy compounds have wide applications and they can be prepared by stoichiometric or catalytic reactions with H2O2 or N2H4 starting from anilines or nitroarenes. In this work, we will present the direct chemoselective hydrogenation of nitroarenes with H2 to give aromatic azoxy compounds under base-free mild conditions, with a bifunctional catalytic system formed by Ni nanoparticles covered by a few layers of carbon (Ni@C NPs) and CeO2 nanoparticles. The catalytic performance of Ni@C-CeO2 catalyst surpasses the state-of-art Au/CeO2 catalyst for the direct production of azoxybenzene from nitrobenzene. By means of kinetic and spectroscopic results, a bifunctional mechanism is proposed in which, the hydrogenation of nitrobenzene can be stopped at the formation of azoxybenzene with >95% conversion and >93% selectivity, or can be further driven to the formation of azobenzene with >85% selectivity. By making a bifunctional catalyst with a non-noble metal, one can achieve chemoselective hydrogenation of nitroarenes not only to anilines, but also to corresponding azoxy and azo compounds.
- Liu, Lichen,Concepción, Patricia,Corma, Avelino
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p. 312 - 323
(2018/12/11)
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- Room temperature catalytic reduction of nitrobenzene to azoxybenzene over one pot synthesised reduced graphene oxide decorated with Ag/ZnO nanocomposite
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We report herein, a one-pot synthetic route for the synthesis of reduced graphene oxide decorated Ag/ZnO nanocomposite and studied its catalytic activity as simple, recyclable and efficient catalyst for one-pot conversion of nitrobenzene to azoxybenzene. It was observed that 5–10 nm Ag-nanoparticles supported on 40–60 nm ZnO nanorod decorated on reduced graphene oxide was formed with a silver loading of 1.6 wt%. The effect of different reaction parameters were investigated and studied in detail. A nitrobenzene conversion of 96% with 98% selectivity of azoxybenzene was achieved without the use of any external additives.
- Paul, Bappi,Vadivel,Yadav, Nishant,Dhar, Siddhartha Sankar
-
-
- Controllable synthesis of azoxybenzenes and anilines with alcohol as the reducing agent promoted by KOH
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Nitrobenzene and its derivatives can be selectively reduced to the corresponding azoxybenzene and aniline compounds with alcohols as the hydrogen source and KOH as the promoter only by simple changes of reaction conditions.
- Wei, Rui Ping,Shi, Feng
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p. 688 - 696
(2019/02/16)
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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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- 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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- Synthesis of Azoxybenzenes by Reductive Dimerization of Nitrosobenzene
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Herein we report an effective and simple preparation method of substituted azoxybenzenes by reductive dimerization of nitrosobenzenes. This procedure requires no additional catalyst/reagent and can be applied to substrates with a wide range of substitution patterns.
- Chen, Yu-Feng,Chen, Jing,Lin, Li-Jen,Chuang, Gary Jing
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p. 11626 - 11630
(2017/11/10)
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- Rh(III)-Catalyzed [4 + 1]-Annulation of Azoxy Compounds with Alkynes: A Regioselective Approach to 2H-Indazoles
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A rhodium-catalyzed regioselective C-H activation/cyclization of azoxy compounds with alkynes has been disclosed to construct a variety of 2H-indazoles. A [4 + 1]-cycloaddition rather than a normal [4 + 2] mode is observed in the process of cyclative capture along with an oxygen-atom transfer and a C≡C triple bond cleavage. This protocol features a broad substrate scope, a good functional group tolerance, and an exclusive regioselectivity.
- Long, Zhen,Yang, Yudong,You, Jingsong
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supporting information
p. 2781 - 2784
(2017/06/07)
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- Factors determining the chemoselectivity of phosphorus-modified palladium catalysts in the hydrogenation of chloronitrobenzenes
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The precursor nature effect on the state of the Pd–P surface layer in palladium catalysts and on their properties in the liquid-phase hydrogenation of chloronitrobenzenes under mild conditions has been investigated. A general feature of the Pd–P-containing nanoparticles obtained from different precursors and white phosphorus at P/Pd = 0.3 (PdCl2 precursor) and 0.7 (Pd(acac)2 precursor) is that their surface contains palladium in phosphide form (BE(Pd3d5/2) = 336.2 eV and BE(Р2р) = 128.9 eV) and Pd(0) clusters (BE(Pd3d5/2) = 335.7 eV). Factors having an effect on the chemoselectivity of the palladium catalysts in chloronitrobenzenes hydrogenation are considered, including the formation of small palladium clusters responsible for hydrogenation under mild conditions.
- Skripov,Belykh,Sterenchuk,Akimov,Tauson,Schmidt
-
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- Room temperature selective reduction of nitrobenzene to azoxybenzene over magnetically separable urchin-like Ni/Graphene nanocomposites
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Magnetically recyclable Ni/Graphene (Ni/G) nanocomposites were synthesized via an in situ reduction growth process for selective reduction of nitroarenes into corresponding azoxybenzene at room temperature and at atmospheric pressure. Here, hydrazine hydrate (N2H4H2O) is used as the reducing agent which generates harmless by-products such as N2 and water. The catalyst, when used under controlled reaction conditions, exhibits a 100% conversion and selectivity to the target product without the use of any external additives (turnover number 36.2). Under the optimized conditions, a variety of structurally different nitroarenes were selectively transformed to their corresponding azoxy products in high conversions. Furthermore, a high stability and recyclability of the catalyst were also observed under the investigated conditions (93% conversion, 100% selectivity after the 4th reuse).
- Pahalagedara, Madhavi N.,Pahalagedara, Lakshitha R.,He, Junkai,Miao, Ran,Gottlieb, Becca,Rathnayake, Dinithi,Suib, Steven L.
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- A Green Chemoenzymatic Process for the Synthesis of Azoxybenzenes
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An efficient chemoenzymatic process for the synthesis of azoxybenzenes was developed. A peracid was generated in situ by Novozym 435, and then a range of anilines were oxidized by the produced peracid to afford azoxybenzenes in yields ranging from 63.1 to 94.1 %. This method expands the application of lipase in organic synthesis and provides an alternative method for the synthesis of azoxybenzenes.
- Yang, Fengjuan,Wang, Zhi,Zhang, Xiaowen,Jiang, Liyan,Li, Yazhuo,Wang, Lei
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p. 3450 - 3453
(2015/11/10)
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- Room temperature selective oxidation of aniline to azoxybenzene over a silver supported tungsten oxide nanostructured catalyst
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Heterogeneous catalysts comprising silver nanoparticles supported on nanostructured tungsten oxide were applied for room temperature oxidative coupling of aniline to azoxybenzene, an important chemical intermediate and a chemical of industrial interest. The catalytic protocol features high activity and selectivity to the target product azoxybenzene with a turnover number of ~368. The catalyst was characterized by XRD, XPS, ICP-AES, FT-IR, TGA, EXAFS, SEM and TEM. The silver-tungsten nanomaterial acts as an excellent catalyst for selective oxidation of aniline to azoxybenzene using H2O2 as an oxidant. An aniline conversion of 87% with 91% selectivity of azoxybenzene was achieved without the use of any external additives. Moreover, a high stability and recyclability of the catalyst is also observed under the investigated conditions. This journal is
- Ghosh, Shilpi,Acharyya, Shankha S.,Sasaki, Takehiko,Bal, Rajaram
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p. 1867 - 1876
(2015/03/18)
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- Silica encapsulated magnetic nanoparticles-supported Zn(II) nanocatalyst: A versatile integration of excellent reactivity and selectivity for the synthesis of azoxyarenes, combined with facile catalyst recovery and recyclability
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A novel and highly efficient zinc based nanocatalyst has been synthesized by covalent grafting of 2-acetylpyridine on amine functionalized silica@magnetite nanoparticles, followed by metallation with zinc acetate. The resulting nano-composite was found to be highly efficient for oxidation of various aromatic amines to give azoxyarenes. The prepared nanocatalyst was characterized by Electron microscopy techniques (SEM and TEM with EDS), X-ray diffraction (XRD), vibrational sampling magnetometer (VSM), Fourier transform infrared spectroscopy (FT-IR) and atomic absorption spectroscopy (AAS) techniques. High turnover number (TON), mild reaction conditions and high selectivity for azoxyarenes with sustained catalytic activity makes present protocol worthy and highly compliant as compared to the other non-magnetic heterogeneous catalytic system. The acquisition of this nanocatalyst is also exemplified by employing the catalyst in leaching and reusability test and the results from the tests showing negligible zinc leaching and recycling was achieved multiple times just by sequestering using an external magnet.
- Sharma,Monga, Yukti
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- Mild, selective and switchable transfer reduction of nitroarenes catalyzed by supported gold nanoparticles
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A highly versatile and flexible gold-based catalytic system has been developed for the controlled and selective transfer reduction of nitroarene using 2-propanol as a convenient hydrogen source under mild conditions. Depending on the specific reaction conditions, multiple products including azoxyarenes, symmetric or asymmetric azoarenes and anilines can be obtained respectively via a controlled reduction of the nitro aromatics with good to excellent yields in the presence of a reusable mesostructured ceria-supported gold (Au/meso-CeO2) catalyst. The overall operational simplicity, high chemoselectivity, functional-group tolerance and reusability of the catalyst make this approach an attractive and reliable tool for organic and process chemists. The Royal Society of Chemistry.
- Liu, Xiang,Ye, Sen,Li, Hai-Qian,Liu, Yong-Mei,Cao, Yong,Fan, Kang-Nian
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p. 3200 - 3206
(2013/12/04)
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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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- Aqueous manganese-mediated reductive coupling of nitroarenes to azoxybenzenes
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Azoxy compounds have been prepared in good yields by reductive coupling of aromatic nitro compounds with manganese and a catalytic amount of acetic acid in aqueous conditions. Copyright Taylor & Francis Group, LLC.
- Dutta, Dilip K.
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p. 1903 - 1906
(2007/10/03)
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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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- Selective reduction of aromatic nitro compounds to azoxy compounds with zinc/aluminium chloride reagent
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Aromatic azoxy compounds have been prepared in good yields by the selective reduction of aromatic nitro compounds with Zn/AlCl3 reagent.
- Dutta, Dilip Kumar
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p. 672 - 673
(2007/10/03)
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- The newborn surface of dull metals in organic synthesis. Bismuth-mediated solvent-free one-step conversion of nitroarenes to azoxy- and azoarenes
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When milled together with bismuth shots, nitroarenes are readily converted to azoxy- and/or azoarenes depending on substrates and conditions employed. Simple extraction with organic solvent followed by evaporation of the resulting dark pasty solid gave the product in good yield.
- Wada, Shinobu,Urano, Mika,Suzuki, Hitomi
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p. 8254 - 8257
(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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- Anti-androgenic activity of substituted azo- and azoxy-benzene derivatives.
-
Substituted phenylazo and phenylazoxy compounds were systematically prepared and their anti-androgenic activity was measured in terms of (1) the growth-inhibiting effect on an androgen-dependent cell line, SC-3, and (2) the binding affinity to nuclear androgen receptor. Generally, azo/azoxy compounds showed cell toxicity, and the growth-inhibiting effects on SC-3 cells correlated with the toxicity. However, some compounds, including 4,4'-dinitroazobenzene (25), 4,4'-dimethoxyazobenzene (33), and 2,2'-dichloroazoxybenzene (47), possessed potent anti-androgenic activity without apparent cell toxicity.
- Takahashi,Ishioka,Koiso,Sodeoka,Hashimoto
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p. 1387 - 1390
(2007/10/03)
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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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- The reaction of 2-chloro-4-nitrophenol and the isomeric chloronitrobenzenes with LDA under aryne-forming conditions
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The unprecedented base-initiated generation of a nitrobenzyne and subsequent addition of preformed arylacetonitrile anion nucleophiles is reported. In all cases, 2-amino-5-nitro-3-benzo[b]furans are obtained as major product with small amounts of 3-arylmethyl-2-cyano-4-nitrophenols. A mechanism involving ring closure of phenoxide and nitrile groups of the initial aryne-nitrile anion adduct is proposed to account for the formation of the benzofurans. The three isomeric chloronitrobenzynes, however, do not give aryne products when treated with LDA, but rather are reduced to the corresponding bis-dichloroazoxybenzenes.
- Tandel, Sagun,Wang, Anlai,Holdeman, Terra C.,Zhang, Hongming,Biehl, Edward R.
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p. 15147 - 15154
(2007/10/03)
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- Synthesis of N-arylhydroxylamines by antimony-catalyzed reduction of nitroarenes
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Metallic antimony catalyzes the reduction of aromatic nitro compounds to the corresponding N-arylhydroxylamines in good yields with NaBH4 under mild conditions. The azoxybenzenes from autoxidation of N-arylhydroxylamines were also obtained in basic conditions.
- Ren, Pingda,Dong, Tingwei,Wu, Shihui
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p. 1547 - 1552
(2007/10/03)
-
- 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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- Catalytic reduction of nitroarenes to azoxybenzenes with sodium borohydride in the presence of bismuth
-
Aromatic nitro compounds have been found to be selectively reduced to axoxy compounds in good yields by NaBH4 in the presence of bismuth powder.
- Ren, Pingda,Pan, Shifeng,Dong, Tingwei,Wu, Shihui
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p. 3903 - 3908
(2007/10/03)
-
- Catalytic selective oxidation of amines with hydroperoxides over molecular sieves: Investigations into the reaction of alkylamines, arylamines, allylamines and benzylamines with H2O2 and TBHP over TS-1 and CrS-2 as the new catalyst
-
The liquid phase oxidation of various substituted amines with dil H2O2 and tert-butyl hydroxyperoxide (TBHP) has been investigated over titanium and chromium silicates respectively. While TS-1/H2O2 combination exhibits a remarkable activity and selectivity in the oxidation of arylamines to produce the symmetrical azoxybenzenes, CrS-2 catalyzes the selective oxidation of various substituted amines to the corresponding nitro compounds by oxidation with 70% TBHP. The nature of the reactive intermediates during the oxidation of anilines to nitrobenzenes has been established using cyclic voltammetry experiments. Further, amines possessing α C-H bonds are selectively oxidized to either oximes or the carbonyl compounds on reaction with H2O2 catalyzed by TS-1.
- Suresh,Joseph,Jayachandran,Pol,Vinod,Sudalai,Sonawane,Ravindranathan
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p. 11305 - 11318
(2007/10/02)
-
- Selective Catalytic Oxidation of Arylamines to Azoxybenzenes with H2O2 over Zeolites
-
Catalytic version of the H2O2-TS-1 combination has been shown to display a good reaction selectivity in the liquid-phase oxidation of anilines to symmetrical azoxybenzenes.
- Sonawane, H. R.,Pol, A. V.,Moghe, P. P.,Biswas, S. S.,Sudalai, A.
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p. 1215 - 1216
(2007/10/02)
-
- Bismuth(III) Chloride-Zinc Promoted Selective Reduction of Aromatic Nitro Compounds to Azoxy Compounds
-
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)
-
- Reduction of Nitroarenes Using an Activated Catalyst Prepared by the Reduction of Nickel Nitrate with Excess Zinc in the Presence of Hydrazine Monohydrate
-
An activated catalyst prepared from a mixture of nickel nitrate hexahydrate with zinc in dry ethanol under reflux showed exceptional catalytic activity for the reduction of nitroarenes to the corresponding azoxy compounds exclusively in the presence of hydrazine monohydrate.However when nickel nitrate hexahydrate was replaced by nickel chloride dihydrate with zinc, only the aminoarenes were formed in high yields.With unactivated catalyst, the reduction reaction from a mixture of nitroarenes, nickel nitrate or chloride, excess zinc and hydrazine monohydrate gave the corresponding azo, azoxy and amino compounds in much lower yields.
- Yun, Tae Ho,Park, Moon Keu,Han, Byung Hee
-
p. 2774 - 2788
(2007/10/02)
-
- Influence of Ion Pairing, Steric Effects, and Other Specific Interactions on the Reactivity of Thioanions with Chloronitrobenzenes. Nucleophilic Aromatic Substitution vs Reduction
-
The reactions in 2-propanol of the isomeric chloronitrobenzenes with thiolate nucleophiles, RS- (R=Me, i-Pr, t-Bu, Ph), have been studied to test for the ability of these representative thioanions of inducing chloride displacement and/or nitro reduction. m-Chloronitrobenzene gives a complex mixture of products, all still retaining the chlorine substituent, via redox processes involving nitro reduction and ring alkylthiolation.In contrast, the ortho and para isomers undergo substitution of chloride according to the addition/elimination SNAr mechanism also when O2 is removed from the reaction environment.Notably, treatment of o- and p-chloronitrobenzene with the oxanion 2-propoxide in oxygen-free i-PrOH results, instead, in nitro reduction.Kinetic and product studies indicate that i-PrS- is more reactive than i-PrO- in both redox and SNAr reactions, the difference in reactivity being, however, considerably greater in the latter process.The MeS- > i-PrS- > PhS- > t-BuS- reactivity order observed in the SNAr reactions is opposite, as far as the aliphatic thiolates are concerned, to the order of basicity.Notably, reactivity drops with increasing bulkiness of the attacking nucleophile.However, kinetic results obtained under conditions of ion paired and of "free" anions and the effects of ion pairing on the kortho/kpara ratios suggest that steric effects in the transition states are scarcely dependent on the bulkiness of the substituent R in the nucleophile RS- and that nucleophilic reactivity is largely determined by the extent of charge concentration on the attacking atom, which, in turn, affects the strength of ion-pairing interactions.
- Montanari, Stefano,Paradisi, Cristina,Scorrano, Gianfranco
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p. 4274 - 4279
(2007/10/02)
-
- 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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p. 3617 - 3621
(2007/10/02)
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- FORMATION OF METHOXY-SUBSTITUTED AZOXYBENZENES IN THE REDUCTION OF NITROARENES IN BASIC METHANOL-TOLUENE SOLUTIONS
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The reduction of nitroarenes in boiling methanol-toluene containing KOH affords high yields of the corresponding azoxy derivative and small amounts of other azoxy compounds containing one or more OCH3 groups linked to the aromatic rings.It has been proved that the reaction does not occur via formation of methoxy-nitroarenes and their further reduction.The reaction is proposed to involve: a) formation of a Meisenheimer complex by attack of the methoxide ion on the nitroarene; b) abstraction of a proton from the Meisenheimer complex by a methoxide ion to form a dianion; c) protonation of the dianion with concurrent elimination of OH to form the nitroso-methoxy arene which is finally reduced to the methoxy-azoxy derivative.It is proposed that the dianion is the electron-donating species to start the reduction of nitro- and nitrosoarenes.
- Prato, Maurizio,Quintily, Ugo,Scorrano, Gianfranco
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p. 421 - 426
(2007/10/02)
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- The synthesis of anilines or azoxybenzenes from the reduction of nitrobenzenes in basic alcoholic media
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Reduction of substituted nitrobenzenes in alkaline alcoholic solutions affords, depending on the experimental conditions used, either anilines or azoxybenzenes in good yields.In the presence of a methylketone, such as acetophenone, the reaction of nitroarenes with aqueous KOH in 2-propanol provides the corresponding anilines in high yields (80-90 percent).On the other hand, when the reaction is carried out in the CH3OH/toluene/KOH system, in the absence of methylketones, the azoxyderivatives are isolated in 70-90 percent yield.
- Prato, Maurizio,Quintily, Ugo,Scapol, Lucia,Scorrano, Gianfranco
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- REACTION OF AROMATIC COMPOUNDS WITH NUCLEOPHILIC REAGENTS IN LIQUID AMMONIA. VII. DIRECTION OF HYDROXYLATION OF 3-SUBSTITUTED (Cl, Br, I, NO2) NITROBENZENES WITH POTASSIUM HYDROXIDE
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The reaction of 3-chloro-, 3-bromo-, and 3-iodonitrobenzenes with potassium hydroxide and oxygen in liquid ammonia (-33 deg C) leads to the formation of nitrohalogenophenols, corresponding to substitution of the hydrogen atom at the orto and para positions of the ring in relation to the nitro group by a hydroxy group.In the case of the last two substrates it also leads to the corresponding 2-halogeno-3',4'-dinitrodiphenylamines.In view of the fact that substitued diphenylamines are formed under the same conditions as a result of the reaction of 3-nitroaniline with 3-halogenonitrobenzenes it is suggested that 3-bromo- and 3-iodonitrobenzenes are partly converted into 3-nitroaniline through the intermediate formation of 3-nitrodehydrobenzene.During dehydroxylation in the absence of oxygen the proportion of the phenols corresponding to substitution of the hydrogen atom at the para position to the nitro group by the hydroxy group increases, and the degree of transformation of the inital compounds decreases. 2,4-Dinitrophenol is formed with a low yield during the reaction of 1,3-nitrobenzene and potassium hydroxide in the presence of oxygen or in an atmosphere of argon.
- Malykhin, E. V.,Kolesnichenko, G. A.,Shteingarts, V. D.
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p. 720 - 726
(2007/10/02)
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- Reduction of Nitroarenes to Anilines in Basic Alcoholic Media
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Substituted nitrobenzenes are reduced by alkoxide ions in alcohols to the corresponding azoxy and aniline derivatives.The reaction leading to anilines has been investigated in detail.Two different processes have been identified, both initiated by the condensation between the nitrosoarene intermediate (the first product of the reduction reaction) and the product of oxidation of the solvent.The imino derivative thus formed (ArN=CH-COR) may either undergo hydrolysis (to aniline) or form, through a series of redox processes, compounds containing the ArNH-CO moiety.These are also hydrolysed to anilines in a slower reaction.
- Prato, Maurizio,Quintily, Ugo,Scorrano, Gianfranco
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p. 1419 - 1424
(2007/10/02)
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- Proximity Effects in Diaryl Derivatives. Part 7. Mechanism of Base-catalysed Rearrangement of 2-(Hydroxyamino)aryl Phenyl Sulphones to 2-Hydroxy-2'-(phenylsulphonyl)azoxybenzenes
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Base-catalysed rearrangement of a 2-(hydroxyamino)aryl phenyl sulphone (1b) to the 2-hydroxy-2'-(phenylsulphonyl)azoxybenzene (4b) was shown by isolation and kinetic studies to be a rapid reaction requiring oxygen; in the absence of oxygen the sulphur-free azoxybenzene (3; R=Cl) was the only product isolated from the reaction of (1c).A mechanism for the formation of 2-hydroxyazoxybenzenes (4) is proposed (Scheme 2) involving dimerization of a nitrosoaryl radical anion (9) to the dianion of an NN-diol (10), and displacement of a phenylsulphonyl group by intramolecular transfer of oxygen from a nitrogen atom.A similar study of the base-catalysed reactions of a 2-(hydroxyamino)aryl phenyl sulphide (12) in the presence of oxygen showed that with a poorer leaving group the bis(phenylthio)azoxybenzene (11; R=SPh) is formed.An improved procedure for the preparation of N-arylhydroxylamines from nitrobenzenes is described.
- Cummings, Robert J.,Grundon, Michael F.,Knipe, Anthony C.,Wasfi, Adil S.
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p. 105 - 108
(2007/10/02)
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- Aryliminodimagnesium Reagents. IV. The Independent Preparation of Unsymmetrically Substituted Azoxyarene Isomers and Their Deoxygenation
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By use of the condensation reaction of aryliminodimagnesium reagents (ArN(MgBr)2) with nitroarenes, six symmetrical and eight unsymmetrical azoxyarenes including four pairs of isomers were prepared in 40-80percent yields.The deoxygenation reaction of the azoxyarenes by treating with five molar equivalents of p-MeOC6H4N(MgBr)2 at 55 deg C in tetrahydrofuran was also studied, and the reactivity of deoxygenation was correlated to the shift of the electronic absorption maximum of azoxyarene.
- Okubo, Masao,Koga, Koji
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p. 203 - 207
(2007/10/02)
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- REDUCTION OF AROMATIC AND ALIPHATIC NITRO COMPOUNDS BY SODIUM HYDROGEN TELLURIDE
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Various nitro compounds were effectively reduced by sodium hydrogen telluride in good yields.Thus, reductive conversion of unhindered nitrobenzenes to azoxybenzenes, sterically hindered nitrobenzenes to anilines, nitroalkanes to dimer of nitrosoalkanes, and vicinal-dinitroalkane to olefin was achieved.
- Osuka, Atsuhiro,Shimizu, Hirohito,Suzuki, Hitomi
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p. 1373 - 1374
(2007/10/02)
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- Kinetics and Mechanisms of the Bamberger Rearrangement. Part 3. Rearrangement of Phenylhydroxylamines to p-Aminophenols in Aqueous Sulphuric Acid Solutions
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The rates of Bamberger-type rearrangement of phenylhydroxylamine (1a) and its derivatives (1b-d) to the corresponding p-aminophenols were determined in sulphuric acid solution.Plots if the pseudo-first-order rate constants against pH (or H0) indicate that the active species at +H2) which exists in equilibrium with the N-protonated species (ArN+H2OH), while the diprotonated species (ArN+H2O+H2) contributes significantly to the observed reaction rate at > 1.00 N (H0 region).The slope of Hammett plots (ρ) which was obtained by plotting kobs at 1.00 N against the Hammett ? values was -3.19.It was also established that the ΔS* values for the four substrates are all positive.These results suggest that the Bamberger rearrangement occurs by an SN1 mechanism and that the elimination of water from ArNHO+H2 is rate determining.
- Sone, Takaaki,Tokuda, Yuuji,Sakai, Toshimi,Shinkai, Seiji,Manabe, Osamu
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p. 298 - 302
(2007/10/02)
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