- Chemoselective electrochemical reduction of nitroarenes with gaseous ammonia
-
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)
-
- Photocatalytic oxidative coupling of arylamines for the synthesis of azoaromatics and the role of O2 in the mechanism
-
The photocatalytic oxidative coupling of aryl amines to selectively synthesize azoaromatic compounds has been realized. Multiple different photocatalysts can be used to perform the general reaction; however, Ir(dF-CF3-ppy)2(dtbpy)+, where dF-CF3-ppy is 2-(2,4-difluorophenyl)-5-(trifluoromethyl)-pyridine and dtpby is 4,4′-tert-butyl-2,2′-bipyridine, showed the greatest range of reactivity with various amine substrates. Both electron-rich and -deficient amines can be coupled with yields up to 95% under an ambient air atmosphere. Oxygen was deemed to be essential for the reaction and is utilized in the regeneration of the photocatalyst. Fluorescence quenching and radical trap experiments indicate an amine radical coupling mechanism that proceeds through a hydrazoaromatic intermediate before further oxidation occurs to form the desired azoaromatic products.
- Sitter, James D.,Vannucci, Aaron K.
-
supporting information
p. 2938 - 2943
(2021/03/01)
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- Single crystal MnOOH nanotubes for selective oxidative coupling of anilines to aromatic azo compounds
-
Catalytic synthesis of aromatic azo compounds by oxidative coupling of anilines using molecular oxygen represents a facile, green and valuable process; however, such an economical process suffers from poor catalytic activity and selectivity. Herein, novel single crystal MnOOH nanotubes with abundant Mn3+sites and high oxygen defects were successfully synthesized. The catalyst exhibited high selectivity for oxidative coupling of anilines, achieving complete transformation into aromatic azo compounds under mild conditions, even at room temperature.
- Cao, Fangxian,Li, Jiayuan,Qu, Yongquan,Zhang, Mingkai,Zhang, Sai,Zou, Yong
-
supporting information
p. 19692 - 19697
(2021/09/20)
-
- Tandem selective reduction of nitroarenes catalyzed by palladium nanoclusters
-
We report a catalytic tandem reduction of nitroarenes by sodium borohydride (NaBH4) in aqueous solution under ambient conditions, which can selectively produce five categories of nitrogen-containing compounds: anilines, N-aryl hydroxylamines, azoxy-, azo- and hydrazo-compounds. The catalyst is in situ-generated ultrasmall palladium nanoclusters (Pd NCs, diameter of 1.3 ± 0.3 nm) from the reduction of Pd(OAc)2 by NaBH4. These highly active Pd NCs are stabilized by surface-coordinated nitroarenes, which inhibit the further growth and aggregation of Pd NCs. By controlling the concentration of Pd(OAc)2 (0.1-0.5 mol% of nitroarene) and NaBH4, the water/ethanol solvent ratio and the tandem reaction sequence, each of the five categories of N-containing compounds can be obtained with excellent yields (up to 98%) in less than 30 min at room temperature. This tunable catalytic tandem reaction works efficiently with a broad range of nitroarene substrates and offers a green and sustainable method for the rapid and large-scale production of valuable N-containing chemicals.
- Yan, Ziqiang,Xie, Xiaoyu,Song, Qun,Ma, Fulei,Sui, Xinyu,Huo, Ziyu,Ma, Mingming
-
supporting information
p. 1301 - 1307
(2020/03/11)
-
- Immobilized antimony species on magnetite: A novel and highly efficient magnetically reusable nanocatalyst for direct and gram-scale reductive-coupling of nitroarenes to azoarenes
-
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
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p. 13112 - 13121
(2019/05/10)
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- Synthesis of Azobenzene Dyes Mediated by CotA Laccase
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An eco-friendly protocol for the synthesis of azobenzene dyes by oxidative coupling of primary aromatic amines is reported. As efficient biocatalytic systems, CotA laccase and CotA laccase/ABTS (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) enable the oxidation of various substituted anilines, in aqueous medium, ambient atmosphere and under mild reaction conditions of pH and temperature. A series of azobenzene dyes were prepared in good to excellent yields in an one-pot reaction. A mechanistic proposal for the formation of the azo derivatives is presented. Our strategy offers an alternative approach for the direct synthesis of azobenzene dyes, avoiding the harsh conditions generally required for most of the traditional synthetic methods.
- Sousa, Ana Catarina,Baptista, Sara R.,Martins, Lígia O.,Robalo, M. Paula
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p. 187 - 193
(2018/12/04)
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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
-
p. 375 - 385
(2019/02/14)
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- Catalytic Nitrene Homocoupling by an Iron(II) Bis(alkoxide) Complex: Bulking Up the Alkoxide Enables a Wider Range of Substrates and Provides Insight into the Reaction Mechanism
-
The reaction of HOR′ (OR′ = di-t-butyl-(3,5-diphenylphenyl)methoxide) with an iron(II) amide precursor forms the iron(II) bis(alkoxide) complex Fe(OR′)2(THF)2 (2). 2 (5-10 mol %) serves as a catalyst for the conversion of aryl azides
- Yousif, Maryam,Wannipurage, Duleeka,Huizenga, Caleb D.,Washnock-Schmid, Elizabeth,Peraino, Nicholas J.,Ozarowski, Andrew,Stoian, Sebastian A.,Lord, Richard L.,Groysman, Stanislav
-
supporting information
p. 9425 - 9438
(2018/08/17)
-
- A Highly Efficient Near-Infrared-Emissive Copolymer with a N=N Double-Bond π-Conjugated System Based on a Fused Azobenzene–Boron Complex
-
Fused azobenzene–boron complexes (BAzs) show highly efficient near-infrared (NIR) emission from the nitrogen–nitrogen double bond (N=N) containing π-conjugated copolymer. Optical measurements showed that BAz worked as a strong electron acceptor because of the intrinsic electron deficiency of the N=N double bond and the boron–nitrogen (B?N) coordination which dramatically lowered the energy of the lowest unoccupied molecular orbital (LUMO) of the azobenzene ligand. The simple donor–acceptor (D–A) type copolymer of bithiophene (BT) and BAz exhibited intense photoluminescence (PL) in the NIR region both in the dilute solution (λPL=751 nm, ΦPL=0.25) and in the film (λPL=821 nm, ΦPL=0.038). The BAz monomer showed slight PL in the dilute solution, and aggregation-induced emission (AIE) was detected. We proposed that N=N double bonds should be attractive and functional building blocks for designing π-conjugated materials.
- Gon, Masayuki,Tanaka, Kazuo,Chujo, Yoshiki
-
supporting information
p. 6546 - 6551
(2018/04/30)
-
- Rh(III)-catalyzed [4?+?1]-annulation of azobenzenes with α- carbonyl sulfoxonium ylides toward 3-acyl-(2H)-indazoles
-
A Rh(III)-catalyzed [4 + 1]-annulation of azobenzenes with α- carbonyl sulfoxonium ylides was developed to access 2H-indazoles in moderate to excellent yields with good functional group compatibilities. It proceeded with the sequential insertion of the Rh(III) carbene to the C?H bond and cyclization steps, where sulfoxonium ylides served as efficient and stable carbene precursor.
- Zhu, Jiawei,Sun, Song,Cheng, Jiang
-
supporting information
p. 2284 - 2287
(2018/05/23)
-
- Convenient Electrocatalytic Synthesis of Azobenzenes from Nitroaromatic Derivatives Using SmI2
-
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
-
p. 8480 - 8486
(2017/12/08)
-
- Impact of Functional Groups on the Copper-Initiated N-Arylation of 5-Functionalized Pyrrolidin-2-ones and Their Vinylogues
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The electronic effects governing the N-arylation of pyrrolidone were investigated. The generalization of our preliminary findings on a copper(I)-catalyzed Csp2-N coupling process was first improved with a wide variety of aryl and heteroaryl halides and methyl pyroglutamate. The optimized protocol was further extended to pyrrolidin-2-ones substituted at the C5-position with an aryl group bearing an electron-donating or electron-withdrawing group as well as to some of their substituted enaminoester vinylogues. The impact of substituents at the N- and C5-position on these coupling processes seemed to be pivotal for determining both the reaction profiles and yields.
- Baudelet, Davy,Da?ch, Adam,Rigo, Beno?t,Lipka, Emmanuelle,Gautret, Philippe,Homerin, Germain,Claverie, Christelle,Rousseau, Jolanta,Abuhaie, Cristina-Maria,Ghinet, Alina
-
p. 2226 - 2244
(2016/07/15)
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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
-
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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- Bismuth nanoparticles: an efficient catalyst for reductive coupling of nitroarenes to azo-compounds
-
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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- A mild CuBr-NMO oxidative system for the coupling of anilines leading to aromatic azo compounds
-
An efficient, mild and cost-effective method has been developed utilizing CuBr with N-methylmorpholine N-oxide (NMO/NMMO) for the oxidative coupling of anilines to access symmetrical and unsymmetrical azo compounds in high yield. The reactivity was found to be governed by electronic and steric factors of anilines.
- Singh, Shikha,Chauhan, Parul,Ravi, Makthala,Taneja, Isha,Wahajuddin,Yadav, Prem. P.
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p. 61876 - 61880
(2015/08/03)
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- Highly efficient synthesis of azos catalyzed by the common metal copper (0) through oxidative coupling reactions
-
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
-
p. 16607 - 16611
(2014/05/06)
-
- Schiff base complexes of rare earth metal ions: Synthesis, characterization and catalytic activity for the oxidation of aniline and substituted anilines
-
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
-
-
- Mg/Triethylammonium formate: A useful system for reductive dimerization of araldehydes into pinacols; Nitroarenes into azoarenes and azoarenes into hydrazoarenes
-
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
-
p. 969 - 974
(2014/03/21)
-
- Meso-tetraphenylironporphyrin(III) chloride catalyzed oxidation of aniline and its substituents by m-chloroperbenzoic acid
-
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
-
p. 1355 - 1360
(2013/06/27)
-
- A facile superoxide induced conversion of aromatic amines to azo compounds under microwave irradiation
-
The present report demonstrates an efficient use of tetraethylammonium superoxide under non-aqueous conditions to bring about a mild and convenient transformation of aromatic amines to azo compounds in good yield under mono-mode microwave irradiation.
- Singh, Sundaram,Singh, Krishna Nand
-
experimental part
p. 841 - 843
(2012/04/04)
-
- Iron(III)-salen-H2O2 as a peroxidase model: Electron transfer reactions with anilines
-
Iron(III)-salen complexes catalyze the H2O2 oxidation of various ring-substituted anilines in MeCN have been studied, and [O=Fe IV(salen)]+? is proposed as the active species. Study of the kinetics of the reaction by spectrophotometry shows the emergence of a new peak at 445 nm in the spectrum which corresponds to azobenzene. Further oxidation of azobenzene by H2O2 leads to the formation of azoxybenzene. ESI-MS studies also support the formation of these products. The rate constants for the oxidation of meta- and para-substituted anilines were determined from the rate of decay of oxidant as well as the rate of formation of azobenzene, and the reaction follows Michaelis-Menten kinetics. The rate data show a linear relationship with the Hammett σ constants and yield a ρ value of -1.1 to -2.4 for substituent variation in the anilines. A reaction mechanism involving electron transfer from aniline to [O=Fe(salen)] +? is proposed. The presence of axial ligands modulates the activity of the complex. Graphical Abstract: [Figure not available: see fulltext.]
- Aslam, Adhem Mohamed,Rajagopal, Seenivasan,Vairamani, Mariappanadar,Ravikumar, Maddula
-
scheme or table
p. 751 - 759
(2012/07/01)
-
- Electrochemical oxidation of o-anisidine, p-anisidine, diphenylamine and o-toluidine at platinum electrode
-
The oxidation of o-anisidine, p-anisidine, diphenylamine and o-toluidine was carried out at constant potential in non-aqueous system at platinum electrode. The electrolysis was carried out at controlled anodic potential in an electrochemical cell assembly containing reaction mixture, working as well as counter electrode and reference electrode. The oxidative products formed during the electrolysis of aromatic amines at platinum anode are discussed and reported here.
- Sharma, Laxmi Kant,Kumar, Sanjeev,Singh,Siddiqui
-
experimental part
p. 1117 - 1123
(2011/05/05)
-
- Catalytic oxidation of primary aromatic amines with sodium periodate catalyzed by Mn(III)salophen complex supported on polystyrene-bound imidazole
-
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
-
experimental part
p. 641 - 645
(2010/12/18)
-
- Concise preparation of azenes by oxidation of aromatic amines with molecular oxygen in subcritical water
-
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
-
experimental part
p. 1089 - 1091
(2012/06/18)
-
- Cupric chloride-catalyzed synthesis of symmetrical azo compounds from primary aromatic amines
-
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
-
experimental part
p. 3428 - 3435
(2009/12/05)
-
- Oxidation of arylaminomagnesium compounds by copper salts
-
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
-
experimental part
p. 124 - 125
(2009/10/15)
-
- Isoquinolinium bromochromate; new, efficient and stable reagent for oxidation of aromatic amines and phenols
-
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.
-
experimental part
p. 1343 - 1346
(2010/08/19)
-
- CuCl-catalyzed aerobic oxidative reaction of primary aromatic amines
-
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
-
p. 4011 - 4015
(2008/09/20)
-
- An efficient and product selective reduction of azoxyarenes into azoarenes or hydrazoarenes by tin/hydrazine hydrate
-
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
-
p. 1086 - 1089
(2007/10/03)
-
- Facile, product-selective reduction of azoxyarenes into azoarenes or hydrazoarenes by aluminium/hydrazine hydrate
-
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
-
p. 2163 - 2168
(2007/10/03)
-
- A facile reduction of azoxyarenes with hydrazine hydrate/magnesium: Formation of different products under different reaction conditions
-
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.
-
p. 772 - 774
(2007/10/03)
-
- A simple and efficient method for the dehydrogenation of symmetric hydrazo compounds with NaNO2-Ac2O
-
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
-
p. 677 - 678
(2007/10/03)
-
- 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
-
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
-
p. 4673 - 4677
(2007/10/03)
-
- The synthesis of azo compounds from nitro compounds using lead and triethylammonium formate
-
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
-
p. 5835 - 5837
(2007/10/03)
-
- Oxidation of primary aromatic amines to azo derivatives with sodium periodate using polystyrene-bound manganese(III) porphyrin
-
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)
-
- Application of lead and ammonium formate as a new system for the synthesis of azo compounds
-
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
-
p. 460 - 462
(2007/10/03)
-
- A simple and efficient method for the dehydrogenation of symmetric hydrazo compounds with NaNo2/NaHSO4·H2O/SiO2
-
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
-
p. 540 - 541
(2007/10/03)
-
- 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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- An exceptionally stable Ti superoxide radical ion: A novel heterogeneous catalyst for the direct conversion of aromatic primary amines to nitro compounds
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A matrix-bound superoxide radical anion, generated by treating Ti(OR)4 (R =iPr, nBu) with H2O2, is a selective heterogeneous catalyst for the oxidation of anilines to the corresponding nitroarenes with 50 % aqueous H2O2 [Eq. (1)]. Yields of 82-98 % are obtained, even with anilines bearing electron-withdrawing substituents (R = NO2, COOH).
- Dewkar, Gajanan K.,Nikalje, Milind D.,Ali, Iliyas Sayyed,Paraskar, Abhimanyu S.,Jagtap,Sudalai
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p. 405 - 408
(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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- Reduction of hydrazines, azo and azoxy compounds, and amine N-oxides with the NiCl2·2H2O-Li-DTBB (cat.) combination
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The NiCl2·2H2O/Li/DTBB (10 mol%) combination allows the reduction of aromatic hydrazines 1 (to amines), azo compounds 2 (to primary amines), azoxy compounds 3 (to azo compounds or to primary amines, depending on the reaction conditions) or amine N-oxides 4 (to tertiary amines), under mild reaction conditions (THF, room temperature). (C) 2000 Elsevier Science Ltd.
- Alonso, Francisco,Radivoy, Gabriel,Yus, Miguel
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p. 8673 - 8678
(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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- A new method for dehydrogenation of symmetric hydrazo compound
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A new synthetic route with N-bromosuccinimide (NBS) and pyridine as oxidation system to dehydrogenate symmetric hydrazo compounds for preparing azo compounds is reported for the first time. Eight azo compounds are prepared in good yields under mild conditions and possible mechanism has been suggested.
- Wang, Cailan,Wang, Xiaoxia,Wang, Yulu
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p. 964 - 965
(2007/10/03)
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- The preparation of symmetrical azobenzenes from anilines by phase transfer catalyzed method
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Used Galvinoxyl as catalyst, the phase transfer catalyzed method of oxidation of primary amines to symmetrical azobenzenes with a saturated solution of potassium ferricyanide in 2N aqueous potassium hydroxide and dichloromethane is described for the first time in this paper. The reaction has intimate relation with Hammett substituent constants. This report offers an efficient and rapid method to prepare azobenzenes and a possible mechanism is also suggested.
- Wang, Xiao-Yang,Wang, Yu-Lu,Li, Jian-Ping,Duan, Zhi-Fang,Zhang, Zi-Yi
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p. 2271 - 2276
(2007/10/03)
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- Phase transfer catalyzed method to prepare symmetrical azobenzenes from anilines
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Using free radical 4-hydroxy-2,2,6,6-tetramethyl-l-piperidinyolxyl as catalyst, the phase transfer catalyzed method of oxidation of anilines to symmetrical azobenzenes with a saturated solution of potassium ferricyanide in 2N aqueous potassium hydroxide and dichloromethane is described for the first time. The reaction has an intimate relation with Hammett substituent constants. This report offers an efficient and rapid method to prepare azobenzenes, and a possible mechanism is also suggested.
- Wang, Xiao-Yang,Wang, Yu-Lu,Wang, Cai-Lan,Li, Jian-Ping,Wang, Hong,Zhang, Zi-Yi
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p. 971 - 974
(2007/10/03)
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- Lack of linear free energy relationship: Tungsten(VI) catalyzed perborate oxidation of anilines
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Operation of linear free energy relationships in tungsten(VI) catalyzed perborate oxidation was studied with 29 para-, meta- and ortho-substituted anilines. The activation parameters were calculated from k*( = rate/[substrate]2) at 35, 40, 45, 50 and 55 °C using the Erying relationship by the method of least squares. The oxidation is not isoentropic; in an isoentropic series only enthalpy of activation determines the reactivity and the isokinetic temperature is at infinity. At the isokinetic temperature all the compounds of the reaction series react at equal rate, the variation of substituent at this temperature has no influence on the free energy of activation.
- Karunakaran,Palanisamy
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p. 571 - 575
(2007/10/03)
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- Efficient Catalytic Oxidation of Primary Aromatic Amines to Azo Derivatives by Manganese(III) Tetraphenylporphyrin
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The oxidation of primary aromatic amines to the corresponding azo derivatives has been observed in catalytic systems containing manganese(III) tetraphenylporphyrin and sodium periodate in the presence of heterocyclic nitrogen bases acting as axial ligands.
- Habibi, Mohammad Hossein,Tangestaninejad, Shahram,Mirkhani, Valiollah
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p. 648 - 649
(2007/10/03)
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- Free Radical Reactions of N-Heterocyclic Compounds, VI. - Radical Reactions of Cyclic 2,2-Diacyl-1-arylhydrazyls. - A New N-N Bond Cleavage Reaction
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Diacylhydrazyl radicals 5 are generated from N-(phenylamino)dicarboximides 1, 2a, b, 3a-f, and 4 by oxidation with different oxidants.The intermediates 5 react in two ways depending on the substituents in the anilino group.Dimerization of the hydrazyl radikals 5 to stable tetrazanes 8 is favoured by acceptor substituents in the Ar group.N-N bond dissoziation (α-decomposition) of the hydrazyl radicals 5 is favoured by donor substituents in the phenyl ring of the anilino group.The fragments of such reactions are imide radicals 22 and phenylnitrenes 23.The formation of these fragmentation products is proven by analysis of the reaction products.The formation of benzoxazole (25) (15percent yield) is an evidence for an intramolecular insertion reaction of the o-methoxyphenylnitrene, generated by oxidation of 3e.The hydrazyl radicals 5 are also trapped by the stable free radical 2,4,6-tri-tert-butylphenoxyl (9).The thermal decomposition of the isolated radical adducts was studied.
- Schulz, Manfred,Kluge, Ralph,Willscher, Sabine
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p. 671 - 678
(2007/10/02)
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