- Azo synthesis meets molecular iodine catalysis
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A metal-free synthetic protocol for azo compound formation by the direct oxidation of hydrazine HN-NH bonds to azo group functionality catalyzed by molecular iodine is disclosed. The strengths of this reactivity include rapid reaction times, low catalyst loadings, use of ambient dioxygen as a stoichiometric oxidant, and ease of experimental set-up and azo product isolation. Mechanistic studies and density functional theory computations offering insight into this reactivity, as well as the events leading to azo group formation are presented. Collectively, this study expands the potential of main-group element iodine as an inexpensive catalyst, while delivering a useful transformation for forming azo compounds.
- Rowshanpour, Rozhin,Dudding, Travis
-
p. 7251 - 7256
(2021/02/26)
-
- Chemoselective electrochemical reduction of nitroarenes with gaseous ammonia
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Valuable aromatic nitrogen compounds can be synthesized by reduction of nitroarenes. Herein, we report electrochemical reduction of nitroarenes by a protocol that uses inert graphite felt as electrodes and ammonia as a reductant. Depending on the cell voltage and the solvent, the protocol can be used to obtain aromatic azoxy, azo, and hydrazo compounds, as well as aniline derivatives with high chemoselectivities. The protocol can be readily scaled up to >10 g with no decrease in yield, demonstrating its potential synthetic utility. A stepwise cathodic reduction pathway was proposed to account for the generations of products in turn.
- Chang, Liu,Li, Jin,Wu, Na,Cheng, Xu
-
supporting information
p. 2468 - 2472
(2021/04/02)
-
- Heterocoupling of Different Aryl Nitrenes to Produce Asymmetric Azoarenes Using Iron-Alkoxide Catalysis and Investigation of the Cis-Trans Isomerism of Selected Bulky Asymmetric Azoarenes
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Heterocoupling of different aryl nitrenes (originating in organoazides) to produce asymmetric azoarenes using two different iron-alkoxide catalysts is reported. Fe(OCtBu2(3,5-Ph2C6H3))2(THF)2 was previously shown to catalyze the homocoupling of a variety of aryl nitrenes. While bulky nitrenes featuring ortho substituents were coupled more efficiently, coupling of the less bulky meta- and para-substituted aryl nitrenes was also demonstrated. In contrast, the iron(II) complex of a chelating bis(alkoxide) ligand, Fe[OO]Ph(THF)2, was previously shown to efficiently couple nonbulky aryl nitrenes lacking substituents in ortho positions. In the present work, we demonstrate that the combination of two different nitrenes (10 equiv overall, 5 equiv each) with Fe(OCtBu2(3,5-Ph2C6H3))2(THF)2 (10 mol %) produced a statistical or close to statistical distribution (25:25:50 for the two homocoupled products and the heterocoupled product, respectively) for various combinations containing one or two ortho alkyl substituents at one nitrene and a single ortho alkyl group at another. Surprisingly, the combination of Fe[OO]Ph(THF)2 with two different nonbulky organoazides was found to primarily catalyze the homocoupling of the resulting aryl nitrenes (21-49%), with a smaller proportion (~8-15%) of asymmetric product formation. Six different heterocoupled products featuring one or two alkyl groups in the ortho positions were isolated as a mixture of cis and trans isomers at room temperature and characterized by NMR spectroscopy, UV-vis spectroscopy, and high-resolution mass spectrometry. Following their isolation, cis-trans isomerism in these species was investigated. Heating the cis-trans mixture to 60 °C produced the trans isomer cleanly, while shining UV light on the cis-trans mixture significantly increased the amount of the cis isomer (up to 90%). The cis isomer was found to be relatively stable, exhibiting t1/2 values of approximately 10 days at room temperature.
- Groysman, Stanislav,Kurup, Sudheer S.,Wannipurage, Duleeka
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p. 3637 - 3644
(2021/11/12)
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- Synthesis of novel 1,2-diarylpyrazolidin-3-one–based compounds and their evaluation as broad spectrum antibacterial agents
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There is a continuous need to develop new antibacterial agents with non-traditional mechanisms to combat the nonstop emerging resistance to most of the antibiotics used in clinical settings. We identified novel pyrazolidinone derivatives as antibacterial hits in an in-house library screening and synthesized several derivatives in order to improve the potency and increase the polarity of the discovered hit compounds. The oxime derivative 24 exhibited promising antibacterial activity against E. coli TolC, B. subtilis and S. aureus with MIC values of 4, 10 and 20 μg/mL, respectively. The new lead compound 24 was found to exhibit a weak dual inhibitory activity against both the E. coli MurA and MurB enzymes with IC50 values of 88.1 and 79.5 μM, respectively, which could partially explain its antibacterial effect. A comparison with the previously reported, structurally related pyrazolidinediones suggested that the oxime functionality at position 4 enhanced the activity against MurA and recovered the activity against the MurB enzyme. Compound 24 can serve as a lead for further development of novel and safe antibiotics with potential broad spectrum activity.
- Abadi, Ashraf H.,Abdel-Halim, Mohammad,El-Sharkawy, Lina Y.,Engel, Matthias,Fathalla, Reem K.,Mokbel, Salma A.
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- Conversion of anilines into azobenzenes in acetic acid with perborate and Mo(VI): correlation of reactivities
-
Azobenzenes are extensively used to dye textiles and leather and by tuning the substituent in the ring, vivid colours are obtained. Here, we report preparation of a large number of azobenzenes in good yield from commercially available anilines using sodium perborate (SPB) and catalytic amount of Na2MoO4 under mild conditions. Glacial acetic acid is the solvent of choice and the aniline to azobenzene conversion is zero, first and first orders with respect to SPB, Na2MoO4 and aniline, respectively. Based on the kinetic orders, UV–visible spectra and cyclic voltammograms, the conversion mechanism has been suggested. The reaction rates of about 50 anilines at 20–50?°C and their energy and entropy of activation conform to the isokinetic or Exner relationship and compensation effect, respectively. However, the reaction rates, deduced by the so far adopted method, fail to comply with the Hammett correlation. The specific reaction rates of molecular anilines, obtained through a modified calculation, conform to the Hammett relationship. Thus, this work presents a convenient inexpensive non-hazardous method of preparation of a larger number of azobenzenes, and shows the requirement of modification in obtaining the true reaction rates of anilines in acetic acid and the validity of Hammett relationship in the conversion process, indicating operation of a common mechanism.
- Karunakaran,Venkataramanan
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p. 375 - 385
(2019/02/14)
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- Rhodium-Catalyzed Reaction of Azobenzenes and Nitrosoarenes toward Phenazines
-
A rhodium-catalyzed annulative reaction between azobenzenes and nitrosoarenes has been developed, leading to a series of phenazines in moderate to good yields. This procedure proceeds with sequential chelation-assisted addition of aryl C-H to nitrosoarenes and ring closure by electrophilic attack of azo group to aryl. During this transformation, the azo group served as not only a traceless directing group but also a building block in the final products.
- Xiao, Yan,Wu, Xiaopeng,Wang, Hepan,Sun, Song,Yu, Jin-Tao,Cheng, Jiang
-
supporting information
p. 2565 - 2568
(2019/04/30)
-
- Immobilized antimony species on magnetite: A novel and highly efficient magnetically reusable nanocatalyst for direct and gram-scale reductive-coupling of nitroarenes to azoarenes
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In this study, magnetic nanoparticles of Fe3O4@SbFx from the immobilization of SbF3 on magnetite were synthesized. The prepared nanocomposite system was then characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry and inductively coupled plasma optical emission spectroscopy. Next, the catalytic activity of Fe3O4@SbFx MNPs was highlighted by one-pot reductive-coupling of aromatic nitro compounds to the corresponding azoarene materials with NaBH4. The reactions were carried out in refluxing EtOH within 6-25 min to afford the products in high yields. The reusability of the Sb-magnetite system was also studied for 6 consecutive cycles without significant loss of catalytic activity. This synthetic protocol provided several advantages in terms of introducing a novel catalytic system based on antimony species for direct and gram-scale preparation of azoarenes from nitroarenes, low loading of the nanocatalyst, mild reaction conditions, using ethanol as a green and economic solvent and high yield of the products.
- Zeynizadeh, Behzad,Faraji, Fariba
-
p. 13112 - 13121
(2019/05/10)
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- Super electron donor-mediated reductive transformation of nitrobenzenes: A novel strategy to synthesize azobenzenes and phenazines
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The transformation of nitrobenzenes into azobenzenes by pyridine-derived super electron donor 2 is described. This method provides an efficient synthesis of azobenzenes because of not requiring the use of expensive transition-metals, toxic or flammable reagents, or harsh conditions. Moreover, when using 2-fluoronitrobenzenes as substrates, phenazines were found to be obtained. The process affords a novel synthesis of phenazines.
- Nozawa-Kumada, Kanako,Abe, Erina,Ito, Shungo,Shigeno, Masanori,Kondo, Yoshinori
-
supporting information
p. 3095 - 3098
(2018/05/22)
-
- Convenient Electrocatalytic Synthesis of Azobenzenes from Nitroaromatic Derivatives Using SmI2
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The synthesis of azobenzenes has been a long-standing challenge. Their current preparation at a preparative or industrial scale requires stoichiometric amounts of environmentally unfriendly reactants. Herein, we demonstrate that the catalytic use of electrogenerated samarium diiodide (SmI2) could promote, in one-step synthesis, the reduction of nitrobenzenes into azobenzenes in high yields under mild reaction conditions. This catalytic procedure contains many elements satisfying a sustainable chemical process for the preparation of one of the most widely wanted family of chemical compounds. The easy synthetic procedure, and the absence of precious metals, bases, and nonhazardous substances, already makes our catalytic procedure a serious alternative to currently available methods. This is a promising method for the efficient synthesis of both symmetrical and asymmetrical azo compounds with a high functional group tolerance.
- Zhang, Yu-Feng,Mellah, Mohamed
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p. 8480 - 8486
(2017/12/08)
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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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- Aromatic amine oxidation process for preparing aromatic azobenzene method
-
The invention relates to a method for preparing an aromatic azo compound by utilizing aromatic amine oxidation. In the method, air or oxygen serves as an oxygen source, and under the effect of a catalyst, aromatic amine is oxidized into the aromatic azo compound. The method is high in oxidization efficiency and product yield; the air or the oxygen serves as the oxygen source, and the method is economical and environmentally friendly. The product and the catalyst can be separated easily, and the aftertreatment is simple. The catalyst is easy to reuse, and the method has very good application prospect.
- -
-
Paragraph 0013; 0017
(2017/10/11)
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- Copper-Manganese Spinel Oxide Catalyzed Synthesis of Amides and Azobenzenes via Aminyl Radical Cations
-
A highly efficient Cu-Mn-catalyzed process for the aminolysis of esters was developed. Also, the catalyst promoted the self- And cross-dehydrogenative coupling of anilines to generate symmetrical and unsymmetrical azobenzenes, respectively. The reactions were performed under neutral conditions with an inexpensive catalyst, gave high yields, and offered wide functional group tolerance. Spinel tap: A novel facet of aminyl radical cation reactivity with esters for the synthesis of amides is presented. The developed method also gives access to symmetrical and unsymmetrical azobenzenes. The reactions are performed under neutral conditions with an inexpensive catalyst, give high yields, and have a wide functional group tolerance.
- Sultan, Shaista,Kumar, Manjeet,Devari, Shekaraiah,Mukherjee, Debaraj,Ali Shah, Bhahwal
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p. 703 - 707
(2016/03/05)
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- The palladium and copper contrast: A twist to products of different chemotypes and altered mechanistic pathways
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A novel contrast in palladium and copper catalysis is revealed to form products of different chemotypes resulting in a phenazine to azoarene twist through an altered mechanistic pathway (from non-radical C-H activation mode of C-N coupling to radical N-N coupling) during the oxidative self-coupling of anilines catalysed by Pd-Ag and Cu-Ag nanoclusters.
- Seth, Kapileswar,Roy, Sudipta Raha,Kumar, Asim,Chakraborti, Asit K.
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p. 2892 - 2896
(2016/05/24)
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- Oxidative coupling of anilines to azobenzenes using heterogeneous manganese oxide catalysts
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We herein report the transition metal oxide-catalyzed synthesis of azobenzenes through the oxidative coupling of anilines. An octahedral molecular sieve of manganese oxide, OMS-2, exhibited the best activity and selectivity. Nine examples of symmetric azobenzenes and twenty unsymmetric ones were synthesized with 62-99% conversion and 64-99% selectivity. In the aniline cross-coupling reactions, the difference of the Hammett constants of two substituted groups (Δσ) determines the selectivity to unsymmetric azobenzenes, which are the major products at Δσ 0.32. In-depth studies reveal that the surface defect sites of the mixed-valence manganese oxide play a key role in facilitating electron transfer and activating molecular oxygen. The single-electron transfer (SET) reaction mechanism is proposed based on electron paramagnetic resonance and X-ray powder diffraction characterization.
- Wang, Min,Ma, Jiping,Yu, Miao,Zhang, Zhe,Wang, Feng
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p. 1940 - 1945
(2016/04/05)
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- Bismuth nanoparticles: an efficient catalyst for reductive coupling of nitroarenes to azo-compounds
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The synthesis of azoarenes from corresponding nitroarenes was developed by virtue of in situ bismuth nanoparticles. A series of aromatic azo compounds can be obtained under mild reaction conditions with excellent yields.
- Pothula, Kishore,Tang, Lin,Zha, Zhenggen,Wang, Zhiyong
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p. 83144 - 83148
(2015/10/19)
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- Deoxygenative coupling of nitroarenes for the synthesis of aromatic azo compounds with CO using supported gold catalysts
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A facile and efficient catalytic system based on a mesostructured ceria-supported gold (Au/meso-CeO2) catalyst was developed for the synthesis of various aromatic azo compounds by the reductive coupling of the corresponding nitroaromatics, using CO as the sole deoxygenative reagent, under additive-free and mild reaction conditions.
- Li, Hai-Qian,Liu, Xiang,Zhang, Qi,Li, Shu-Shuang,Liu, Yong-Mei,He, He-Yong,Cao, Yong
-
supporting information
p. 11217 - 11220
(2015/07/07)
-
- Graphene oxide supported MnO2 nanorods: An efficient heterogeneous catalyst for oxidation of aromatic amines to azo-compounds
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Graphene oxide supported MnO2 nanorods (GOnc), a composite material, has been synthesized and characterized by XRD, FE-SEM, EDX, BET surface area measurement, FTIR and Raman Spectroscopy. The composite material (GOnc) was found to be a highly efficient, reusable and cost effective heterogeneous catalyst for the one-pot, selective synthesis of azo-compounds from aromatic amines under an N2 atmosphere. After completion of the reaction, the catalyst is readily recovered by filtration and can be reused at least three times without significant loss in activity. This journal is
- Kumari, Shweta,Shekhar, Amiya,Pathak, Devendra D.
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p. 61187 - 61192
(2015/02/19)
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- Highly efficient synthesis of azos catalyzed by the common metal copper (0) through oxidative coupling reactions
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A facile and efficient approach to synthesize symmetric, asymmetric and bridged aromatic azo compounds (AAzos) from aromatic amines was developed by using red copper as catalyst. Despite numerous efforts towards the catalytic synthesis of symmetric and asymmetric AAzos derivatives, most reactions present certain drawbacks inhibiting their industrial applications, such as laborious multi-step processes, harsh reaction conditions and expensive reagents. And the synthesis of bridged azos had low yields before. With the presence of ammonium bromide as co-catalyst, pyridine as a ligand and molecular dioxygen as a sole oxidative reagent, red copper, a common and abundant metal in nature, exhibited unexpected catalytic activity towards the preparation of AAzos in high yields via one-step reaction, making this catalyst an attractive candidate for industrial and synthetic applications.
- Wang, Jiaqing,He, Jing,Zhi, Cong,Luo, Bin,Li, Xinming,Pan, Yue,Cao, Xueqin,Gu, Hongwei
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p. 16607 - 16611
(2014/05/06)
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- Schiff base complexes of rare earth metal ions: Synthesis, characterization and catalytic activity for the oxidation of aniline and substituted anilines
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Several new lanthanide complexes of Pr(III), Sm(III), Gd(III), Tb(III), Er(III) and Yb(III) with the sodium salt of the Schiff base, 2-[(5-bromo-2-hydroxy-benzylidene)-amino]-5-methyl-pentanoic acid, derived from leucine and 5-bromosalicylaldehyde have been synthesized. These complexes having general formula [Ln(HL)(NO3)2(H2O)] ·NO3 were characterized by elemental analysis, UV-vis., FT-IR, EPR, Mass spectrometry and Thermal analysis. The FT-IR spectral data suggested that the ligand behaves as a tridentate ligand with one nitrogen and two oxygen donor atoms, sequence towards central metal ion. From the analytical data, the stoichiometry of the complexes was found to be 1:1 (metal:ligand). The physico-chemical data suggested eight coordination number for Ln(III) Schiff base complexes. Thermal behaviour (TGA/DTA) and fluorescence nature of the complexes were also studied. The Gd(III) Schiff base complex was found to be an efficient catalyst for the oxidation of aniline and substituted anilines under mild conditions.
- Lekha,Kanmani Raja,Rajagopal,Easwaramoorthy
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- An efficient catalyst-free and chemoselective synthesis of azobenzenes from nitrobenzenes
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NaOH mediated reaction of nitrobenzenes in EtOH was performed at 80 °C temperature affording azobenzenes in excellent yield. This methodology presents an easy synthesis of a wide variety of azo compounds from readily available nitrobenzene derivatives. This journal is
- Gund, Sitaram H.,Shelkar, Radheshyam S.,Nagarkar, Jayashree M.
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p. 42947 - 42951
(2015/02/19)
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- Gold-catalyzed direct hydrogenative coupling of nitroarenes to synthesize aromatic azo compounds
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The azo linkage is a prominent chemical motif which has found numerous applications in materials science, pharmaceuticals, and agrochemicals. Described herein is a sustainable heterogeneous-gold-catalyzed synthesis of azo arenes. Available nitroarenes are deoxygenated and linked selectively by the formation of N-N bonds using molecular H2 without any external additives. As a result of a unique and remarkable synergy between the metal and support, a facile surface-mediated condensation of nitroso and hydroxylamine intermediates is enabled, and the desired transformation proceeds in a highly selective manner under mild reaction conditions. The protocol tolerates a large variety of functional groups and offers a general and versatile method for the environmentally friendly synthesis of symmetric or asymmetric aromatic azo compounds.
- Liu, Xiang,Li, Hai-Qian,Ye, Sen,Liu, Yong-Mei,He, He-Yong,Cao, Yong
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supporting information
p. 7624 - 7628
(2014/08/05)
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- One-pot preparation of azobenzenes from nitrobenzenes by the combination of an indium-catalyzed reductive coupling and a subsequent oxidation
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We demonstrated how a reduction step with a reducing system comprised of In(OTf)3 and Et3SiH and a subsequent oxidation that occurred under an ambient (oxygen) atmosphere allowed the highly selective and catalytic conversion of aromatic nitro compounds into symmetrical or unsymmetrical azobenzene derivatives. This catalytic system displayed a tolerance for the functional groups on a benzene ring: an alkyl group, a halogen, an acetyl group, an ester, a nitrile group, an acetyl group, an ester moiety, and a sulfonamide group.
- Sakai, Norio,Asama, Shun,Anai, Satsuki,Konakahara, Takeo
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p. 2027 - 2033
(2014/03/21)
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- Mg/Triethylammonium formate: A useful system for reductive dimerization of araldehydes into pinacols; Nitroarenes into azoarenes and azoarenes into hydrazoarenes
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Studies are reported which describes the effectiveness of triethylammonium formate in the presence of magnesium for the efficient intermolecular pinacol coupling using MeOH as solvent, Various aromatic carbonyls underwent smooth reductive coupling to give the corresponding I ,2-diols. A series of azo compounds were obtained by the reductive coupling of nitroaromatics while azo compounds were reduced to the corresponding hydrazoarenes by this system. There was no adverse effect on the other reducible and hydrogenolysable groups such as ether linkage, hydroxy and halogens. The reactions are clean, high yielding and inexpensive. All the reactions proceeded smoothly at ambient temperature.
- Pamar, M. Geeta,Govender,Muthusamy,Krause, Ruiw M.,Nanjundaswamy
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p. 969 - 974
(2014/03/21)
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- Palladium-catalysed transfer hydrogenation of aromatic nitro compounds - An unusual chain elongation
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Aromatic nitro compounds are reduced via transfer hydrogenation in the presence of palladium on magnesium-lanthanum mixed oxide support in ethanol yielding the corresponding amines. With several acetophenone derivatives, the reduction was accompanied by c
- Németh, János,Kiss, árpád,Hell, Zoltán
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p. 6094 - 6096
(2013/10/22)
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- The effect of water on the hydrogenation of o-chloronitrobenzene in ethanol, n-heptane and compressed carbon dioxide
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Water as a clean solvent and promoter in the organic synthesis have attracted more attention, herein the effect of water was studied for the hydrogenation of o-chloronitrobenzene (o-CNB) over Pt/C and Pd/C catalysts in ethanol, n-heptane and compressed CO2. Very interesting, the reaction rate decreased in ethanol, but increased in n-heptane and compressed CO 2 with the addition of water. The role of water in the reaction was mainly discussed from the experimental data and phase behavior analysis, one is to activate the functional group of NO2 through the interactions via a hydrogen bonding, and the other is to affect the solubility of hydrogen in ethanol and n-heptane. The positive effect of the interaction between water and reactants may be counteracted by the negative effect of hydrogen solubility in ethanol. However, the concentration of o-CNB and hydrogen changed slightly in n-heptane with the addition of water, so the interaction of water with reactants may play a main role in improving the TOF. The combination of H2O and CO2 is more efficient than the pure H2O, CO 2 and H2O-n-heptane systems. The phase behavior may play important role also for the improved activity except for the interactions of H2O and CO2 with the reactants. o-CNB phase was expanded in the compressed CO2 and so the concentration of H2 in o-CNB phase increased due to the miscible of CO2 and H2, resulting in the enhancement of reaction rate and the maximum conversion at pressure of 9 MPa CO2, at which the volume was expanded to the largest one. The similar results were also obtained in the compressed CO 2 system without H2O. In addition, the stability of Pt/C and Pd/C was studied in H2O-n-heptane and H2O-CO 2. As a result, the H2O-CO2 media and Pt/C catalyst is one of the most effective systems for the hydrogenation of o-CNB.
- Cheng, Haiyang,Meng, Xiangchun,Yu, Yancun,Zhao, Fengyu
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- Organocatalytic oxidative dehydrogenation of aromatic amines for the preparation of azobenzenes under mild conditions
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(Diacetoxyiodo)benzene used as stoichiometrically and catalytically in the preparation of azobenzenes under mild reaction conditions was developed. The metal-free oxidation systems demonstrated wide substituents tolerance, alkyls, halogens, and several versatile functional groups, such as amino, ethynyl, and carboxyl substituents are compatible well, and the corresponding products could be formed with good to excellent yields. In this disclosed method, the more large scale formation of azo compounds also could be carried out successfully. Of note that 3-ethynylbenzenamine applied as a very useful cross dehydrogenative partner, which coupled with different anilines, providing asymmetrical azo compounds with acceptable yields in one step under very mild reaction conditions.
- Ma, Hengchang,Li, Wenfeng,Wang, Jian,Xiao, Guanghai,Gong, Yuan,Qi, Chunxuan,Feng, Yunpeng,Li, Xiufang,Bao, Zhikang,Cao, Wei,Sun, Qiangsheng,Veaceslav, Caraus,Wang, Feng,Lei, Ziqiang
-
experimental part
p. 8358 - 8366
(2012/09/21)
-
- Meso-tetraphenylironporphyrin(III) chloride catalyzed oxidation of aniline and its substituents by m-chloroperbenzoic acid
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The most fascinating feature of heme-enzymes such as cytochromes P450 is their ability to carry out oxidations with high selectivity. Metalloporphyrin complexes are used as replicate compounds for cytochrome P450. A kinetic analysis has been carried out with the aim of understanding the mechanistic studies on oxidation of anilines by m-chloroperbenzoic acid catalyzed by meso-tetraphenylironporphyrin(III) chloride in aqueous acetic acid medium. The order of the reaction is found to be second order with respect to the substrate and first order with respect to the catalyst and oxidant. Product analysis proves that azobenzene is the sole product in the catalytic oxidation. The increase of [H+] in this oxidation retards the rate of the reaction. The effects of substituents on the oxidation rate are studied with 19 ortho-, meta- and para- substituted anilines at five different temperatures. The thermodynamic parameters for the oxidation have been determined and discussed. The catalysed m-chloroperbenzoic acid oxidation with substituted anilines fulfills the isokinetic relationship and Exner correlation but not to any of the linear free energy relationships. The solvent interaction also plays a major role in leading the reactivity. Based on the kinetic results and product analysis a probable mechanism is proposed.
- Raja,Karunakaran
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p. 1355 - 1360
(2013/06/27)
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- Catalytic oxidation of primary aromatic amines with sodium periodate catalyzed by Mn(III)salophen complex supported on polystyrene-bound imidazole
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The catalytic activity of Mn(III)salophen complex supported on polystyrene-bound imidazole, [Mn(salophen)Cl-PSI], was studied in the oxidation of primary aromatic amines in acetonitrile/water, using sodium periodate as an oxygen source. Amines were oxidized efficiently to their corresponding azo derivatives in the presence of this catalyst. The heterogeneous catalyst showed high stability and reusability in the oxidation reactions and could be reused several times without loss of its activity. The effect of different solvents was studied in the oxidation of p-toluidine and CH3CN/H2O was chosen as the solvent.
- Mirkhani,Moghadam,Tangestaninejad,Hajibagheri
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experimental part
p. 641 - 645
(2010/12/18)
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- Concise preparation of azenes by oxidation of aromatic amines with molecular oxygen in subcritical water
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Reaction of organic substrates with molecular oxygen, the most abundant and accessible oxidant, has always been an attractive method for preparation of target molecules. In terms of green chemistry, non-metal-catalyzed oxidation of organic substrates is very attractive. This paper describes a general procedure for synthesis of azenes by oxidation of primary aromatic amines with molecular oxygen (3O2) in subcritical water. The reactions afforded the corresponding azenes in moderate to good yield. Springer-Verlag 2010.
- Kus, Nermin Simsek
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experimental part
p. 1089 - 1091
(2012/06/18)
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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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- Selective hydrogenation of chloronitrobenzene to chloroaniline in supercritical carbon dioxide over Ni/TiO2: Significance of molecular interactions
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The hydrogenation of chloronitrobenzene to chloroaniline was investigated over Ni/TiO2 at 35 °C in supercritical CO2 (scCO2), ethanol, and n-hexane. The reaction rate followed the order of scCO2 > n-hexane > eth
- Meng, Xiangchun,Cheng, Haiyang,Fujita, Shin-ichiro,Hao, Yufen,Shang, Yanjiao,Yu, Yancun,Cai, Shuxia,Zhao, Fengyu,Arai, Masahiko
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scheme or table
p. 131 - 139
(2010/09/17)
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- Oxidation of arylaminomagnesium compounds by copper salts
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Oxidation of arylaminomagnesium compounds by cupric chloride has been investigated. A possible oxidation reaction mechanism is considered.
- Zhang, Ming,Zhang, Rongli,Zhang, Ai-Qin,Zhao, Yongli,Wang, Tao
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experimental part
p. 124 - 125
(2009/10/15)
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- Cupric chloride-catalyzed synthesis of symmetrical azo compounds from primary aromatic amines
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Symmetrical azo compounds were synthesized from primary aromatic amines using n-BuMgBr as a base, oxygen as an oxidant, and CuCl2 as a catalyst.
- Zhang, Ming,Zhang, Rongli,Zhang, Ai-Qin,Li, Xinfei,Liang, Haihua
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experimental part
p. 3428 - 3435
(2009/12/05)
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- Isoquinolinium bromochromate; new, efficient and stable reagent for oxidation of aromatic amines and phenols
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The new chromium(VI) oxidizing reagent isoquinolinium bromochromate (IQBC) was prepared and characterized. This new compound has been found to be an efficient reagent for oxidation of primary amines and phenols. The oxidation of primary amines and phenols with isoquinolinium bromochromate proceeded smoothly to afford corresponding azobenzenes and quinones in good to excellent yield. The synthesized isoquinolinium bromochromate is more ideal reagent, with number of specifications including higher yield, mild conditions and easy preparation. The results obtained with isoquinolinium bromochromate are satisfactory and suggest that this new reagent is valuable addition to the existing chromium(VI) reagents.
- Khansole, Sandeep V.,Patwari, Shivaji B.,Vibhute, Yeshwant B.
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experimental part
p. 1343 - 1346
(2010/08/19)
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- CuCl-catalyzed aerobic oxidative reaction of primary aromatic amines
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The oxidations of primary aromatic amines were investigated. Cuprous chloride-air system can catalyze the oxidation of primary aromatic amines to azo derivatives, anils, and/or quinone anils. The experimental procedure is simple and the products could be easily isolated in high yields.
- Lu, Wenchao,Xi, Chanjuan
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p. 4011 - 4015
(2008/09/20)
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- An efficient and product selective reduction of azoxyarenes into azoarenes or hydrazoarenes by tin/hydrazine hydrate
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A general and rapid method is described for the reduction of azoxyarenes to give the corresponding hydrazoarenes under microwave irradiation and azoarenes at reflux conditions on treatment with hydrazine hydrate in the presence of tin metal in methanol. The reactions are found to be fast and clean, give excellent yield and high purity of the products. Ether linkage and Cl are unaffected.
- Nanjundaswamy,Pasha
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p. 1086 - 1089
(2007/10/03)
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- Facile, product-selective reduction of azoxyarenes into azoarenes or hydrazoarenes by aluminium/hydrazine hydrate
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Azoxyarenes, on treatment with hydrazine hydrate in presence of aluminium powder in methanol, undergo reduction. The reactions have been carried under microwave irradiation as well at reflux to get the corresponding hydrazoarenes and azoarenes as reduced products. The reaction is very fast, which gives excellent yield of the product. Substituents such as OCH3, OC 2H5, and Cl are unaffected. Copyright Taylor & Francis, Inc.
- Nanjundaswamy,Pasha
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p. 2163 - 2168
(2007/10/03)
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- A facile reduction of azoxyarenes with hydrazine hydrate/magnesium: Formation of different products under different reaction conditions
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Azoxyarenes on treatment with hydrazine hydrate in presence of magnesium turnings in methanol undergo reduction. The reactions have been carried under microwave irradiation as well as at reflux to give the corresponding hydrazoarenes and azoarenes as reduced products. The reactions are very fast and give excellent yields of the products. Substituents like OCH3, OC2H5 and Cl are unaffected.
- Nanjundaswamy, Hemmaragala M.,Pasha, Mohamed A.
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p. 772 - 774
(2007/10/03)
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- Cytochrome P-450 dependent monooxygenases model system: Rapid and efficient oxidation of primary aromatic amines to azo derivatives with sodium periodate catalyzed by manganese(III) Schiff base complexes
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Rapid and efficient oxidation of primary aromatic amines was investigated. Mn(III)-salophen catalyst can catalyze the oxidation of primary aromatic amines to azo derivatives with sodium periodate. The ability of various Schiff base complexes in this oxidation system was also investigated.
- Mirkhani, Valiollah,Tangestaninejad, Shahram,Moghadam, Majid,Moghbel, Maryam
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p. 4673 - 4677
(2007/10/03)
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- A simple and efficient method for the dehydrogenation of symmetric hydrazo compounds with NaNO2-Ac2O
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Rapid oxidation of eighteen symmetric hydrazo compounds to corresponding azo compounds using NaNO2-acetic anhydride as a novel oxidizing agent under mild condition is reported for the first time.
- Li, Xiaochuan,Wang, Yulu,Wang, Jinye
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p. 677 - 678
(2007/10/03)
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- Facile synthesis of azo compounds from aromatic nitro compounds using magnesium and triethylammonium formate
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Magnesium/triethylammonium formate is a convenient reagent for the reduction of aromatic nitro compounds to corresponding symmetrically substituted azo compounds. Various azo compounds containing additional reducible substituents, including halogen, nitrile, acid, phenol, ester, and methoxy functions, have been synthesized in a single step by the use of this reagent. The conversion is reasonably fast, clean, high yielding, and occurs at room temperature in methanol.
- Srinivasa,Abiraj,Gowda, D. Channe
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p. 609 - 610
(2007/10/03)
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- Reactions of nitrosoarenes containing electron-withdrawing substituents with coordinated CO. Synthesis and structure of complexes Pd2(OAc) 2(p-ClC6H4N[p-ClC6H 3NO])2 and Pd2(OAc)2(o-ClC 6H4N[o-ClC6H3NO])2
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The reaction of tetranuclear Pd4(μ-COOCH3) 4(μ-CO)4 cluster (1a) with p- and o- chloronitrosobenzenes was found to give dinuclear nitrosoamide complexes, Pd2(OAc)2(p-ClC6H4N[p-ClC 6H3NO])2 (4) and Pd2(OAc) 2(o-ClC6H4N[o-ClC6H 3NO])2 (5), respectively. The formation of complexes 4 and 5 is accompanied by evolution of CO2, resulting from oxidation of CO coordinated in cluster 1. Complexes 4 and 5 were characterized by elemental analysis and IR and 1H NMR spectroscopy; their structures were studied by EXAFS. The reactions of dinuclear complex 4 with molecular hydrogen and CO were studied. The major products of reduction of 4 with hydrogen include metallic palladium, acetic acid, cyclohexanone, and molecular nitrogen. Treatment of complex 4 with CO under mild conditions (1 atm, 20°C) affords p-chlorophenyl isocyanate.
- Orlova,Stromnova,Kazyul'kin,Boganova,Kochubey,Novgorodov
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p. 819 - 824
(2007/10/03)
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- Oxidation of primary aromatic amines to azo derivatives with sodium periodate using polystyrene-bound manganese(III) porphyrin
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The manganese (III) complex of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin covalently bound to crosslinked chloromethylated polystyrene [Mn(H 2NTPP)-CMP] can act as an efficient catalyst for oxidation of primary aromatic amines to the corresponding azo compounds by sodium periodate in the presence of imidazole as axial ligand.
- Mirkhani, Valiollah,Tangestaninejad, Shahram,Moghadam, Majid,Karimian, Zohreh
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p. 792 - 794
(2007/10/03)
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- The synthesis of azo compounds from nitro compounds using lead and triethylammonium formate
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Aromatic nitro compounds were reduced to the corresponding symmetrically substituted azo compounds using lead as catalyst and triethylammonium formate as hydrogen donor. Various azo compounds containing additional reducible substituents including halogens, nitrile, acid, phenol, ester, methoxy functions, etc, have been synthesized in a single step by the use of this reagent. The conversion is reasonably fast, clean, high yielding and occurs at room temperature in methanol.
- Srinivasa,Abiraj,Gowda, D. Channe
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p. 5835 - 5837
(2007/10/03)
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- Mechanism and reactivity in perborate oxidation of anilines in acetic acid
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Perborate but not percarbonate in acetic acid generates peracetic acid on standing and the peracetic acid oxidation of anilines is fast. The oxidation with a fresh solution of perborate in acetic acid is smooth and second order but the specific oxidation rate increases with increasing [perborate]0 or [boric acid]. Perborate on dissolution affords hydrogen peroxide and a borate; the latter assists the former in the oxidation. The oxidation rates of anilines under identical conditions do not conform to any of the linear free energy relationships but the reaction rates of molecular anilines do. Perborate oxidation proceeds via two reaction paths but the overall oxidation rates of molecular anilines conform to structure reactivity relationships; the transition states do not differ significantly. Analysis of the oxidation rates of perborate and percarbonate reveals that while perborate oxidation is faster than percarbonate it is at least as selective as the latter.
- Karunakaran, Chockalingam,Kamalam, Ramasamy
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p. 2011 - 2018
(2007/10/03)
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- A simple and efficient method for the dehydrogenation of symmetric hydrazo compounds with NaNo2/NaHSO4·H2O/SiO2
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In this paper, 18 symmetric hydrazo compounds undergo rapid oxidation to corresponding azo compounds using NaNO2/NaHSO4·H2O/SiO2 as a novel oxidising agent under mild conditions for the first time.
- Li, Xiao-Chuan,Wang, Yu-Lu,Wang, Jin-Ye
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p. 540 - 541
(2007/10/03)
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- Application of lead and ammonium formate as a new system for the synthesis of azo compounds
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Aromatic nitro compounds containing additional reducible substituents such as acid, phenol, halogen, ester functions are reduced to the corresponding symmetrically substituted azo compounds by employing lead and ammonium formate in methanol or tetrahydrofuran or dioxane medium at reflux temperature. The conversion occurs without hydrogenolysis or hydrogenation of -Cl, -OCH3, -OC2H5, -CO2H, moieties, which are prone to undergo reduction. The conversion is reasonably fast, clean and high yielding.
- Gowda, Shankare,Gowda, D. Channe
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p. 460 - 462
(2007/10/03)
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- A simple, efficient phase-transfer catalyzed method for preparing symmetrical azobenzenes from anilines
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Using 2,4,6-tri-tert-butylphenol as catalyst, the phase transfer catalyzed oxidation of anilines to symmetrical azobenzenes is described for the first time. The ease of oxidation coincides with the Hammett substituent constants. This report offers an efficient and rapid method to prepare azobenzenes. A possible mechanism involving free radical oxidation is also suggested.
- Wang,Wang,Li,Wang,Duan,Zhang
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p. 545 - 547
(2007/10/03)
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- Anti-androgenic activity of substituted azo- and azoxy-benzene derivatives.
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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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