Search

We report for the first time a stable and easily recoverable catalytic system that achieves an entirely mutual transformation of azobenzene and hydrazobenzene under very mild conditions. [Display omitted] • A stable catalytic system achieves hydrogenation/dehydrogenation cycles. • Hydrogenation/dehydrogenation reactions proceed under very mild conditions. • Dehydrogenation reaction proceeds with hydrogen as the by-product. Azobenzene and hydrazobenzene compounds are essential intermediates for synthesizing pharmaceuticals and dyes. Meanwhile, the hydrazobenzene/azobenzene couple is a potential hydrogen storage system when both the dehydrogenation of hydrazobenzene and the hydrogenation of azobenzenes can be achieved under mild reaction conditions. In this work, we report an entirely mutual transformation of azobenzene and hydrazobenzene under very mild conditions using porous BN supported Cu nanoparticles (Cu/PBN) as the catalyst for the first time. Direct oxidative dehydrogenation reaction proceeded in the open air with the removal of molecular hydrogen as the by-product and a wide range of hydrazobenzenes readily undergoes dehydrogenation, resulting in an excellent yield of the corresponding azobenzene. [ABSTRACT FROM AUTHOR]

Each of the three new hydrazobenzenes consisting of a hydrazobenzene conjugated with a 5-membered heterocyclic ring (furan or thiophene) at its two para positions, prepared from corresponding azo precursors, was used in the acid-catalyzed benzidine rearrangements. Both rearrangement and disproportionation occurred and product structures were characterized by spectroscopic data such as NMR, MS, and with CHN analysis. We confirm the largest [9, 9]-sigmatropic benzidine-type rearrangement in each case as a prominent pathway accompanied by disproportionation. [ABSTRACT FROM AUTHOR]

Visible-light irradiation (λ ＜ 600 nm) of commercially-available CdS in alcohol successfully promotes hydrogenation of azobenzene to hydrazobenzene with more than 95% selectivity. This is promoted by strong adsorption of azobenzene to the photoformed zerovalent Cd species adjacent to the surface S vacancies on CdS; this leads to efficient reduction to hydrazobenzene. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of nitrobenzene and other members of the nitrobenzene family (nitrosobenzene, azoxybenzene, azobenzene) has been investigated in DMF/TEAP by cyclic voltammetry, polarography, and controlled potential electrolysis at mercury, platinum, copper, and nickel cathodes. At the four electrodes, nitrobenzene and the other members of the family are reduced to aniline via hydrazobenzene upon exhaustive electrolysis at −2.35 V vs. Ag/AgNO3 (0,05 M). The electrochemical reversibility of the nitrobenzene/nitrobenzene radical anion and of the azoxybenzene/azoxybenzene radical anion couples is decreased by the presence of oxides at the surface of copper and nickel. The presence of oxides has little influence on the reversibility of the nitrosobenzene/nitrosobenzene radical anion and azobenzene/azobenzene radical anion couples. [ABSTRACT FROM AUTHOR]

A series of substituted N,N′-diarylhydrazines (ArNHNHAr), Ar = 3,5-(CH3)-C6H3; -Ph; 4-Cl-C6H4; 3,5-Cl-C6H3; 3,5-(CF3)-C6H3, were reacted with Ce(iii)[N(SiMe3)2]3 and lithiated bases to explore the use of Ce(iii) as a reductant and to evaluate the impact of the ligand substitution on the electronic structure at the cerium metal centre of the resulting complexes. The N,N′-diarylhydrazido ligands were coordinated by the Li+ cation and then reduced by a Ce(iii) cation to form Li4(Et2O)4[CeIV(ArNNAr)4] complexes in all cases. Stabilization of the resulting Ce(iv) product depended on the substituents on the N,N′-diarylhydrazido ligands. Isolable cerium products formed only with electron withdrawing substituents on the N,N′-diarylhydrazido rings, whereas electron donating substituents resulted in intractable mixtures of Ce(iii) products and N,N′-bis(aryl)diazenes (ArN=NAr). The presence of electron withdrawing substituents at the N,N′-diarylhydrazido ligands formed relatively electron poor Ce(iv) complexes, which were probed by UV-Vis spectroscopy, cyclic voltammetry, and DFT calculations. The Lewis acid promoted reduction of hydrazobenzene derivatives by Ce(iii) was thus demonstrated to be a successful method to access electron poor cerium(iv) complexes. [ABSTRACT FROM AUTHOR]

When treated with dilute inorganic acids N , N ′-diarylhydrazines (hydrazobenzenes) with an alkyl substituent in the 4-position undergo [5,5]-sigmatropic rearrangement reactions to furnish 4-(4′-aminophenyl)-4-alkylcyclohexa-2,5-dienimines ( ipso -benzidines) in moderate to excellent yields. Steric bulk of the 4-alkyl substituent in the starting material decreases the yield of the respective ipso -benzidine. Additional electron-donating alkyl substituents in the ortho - and/or meta -positions on both rings generally promote the reaction and consequently increase the yield of the 4.4′-benzidine rearrangement product. Described herein are our findings regarding the scope and limits of this unusual benzidine rearrangement. [ABSTRACT FROM AUTHOR]

Electron transfer in azobenzene derivatives bearing two carboxylic acid groups is coupled with intramolecular proton transfer in a stepwise manner in the title 2e− + 2H+ redox couple. The presence of the pendant acid—base functions pushes the redox chemistry of the azo/hydrazo couple toward positive potentials by as much as 0.75 V. This is essentially the result of H-bonding of one of the nitrogen atoms by the neighboring carboxylic group and H-bonding of one carboxylate by the neighboring protonated nitrogen atom. The two electron-transfer reactions, particularly the second one, are accompanied by strong structural changes, which results in the occurrence of a square scheme mechanism in which electron transfer and structural change are not concerted. These are typical phenomena that are likely to be encountered when attempting to boost proton-coupled electron-transfer stoichiometric or catalytic processes by installing pendant acid—base functionalities in the close vicinity of the reacting center. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, 2,2′-dichlorohydrazobenzene was synthesized by the electrochemical reduction of o-chloronitrobenzene using the ion-exchange membrane method. The effects of different catalysts (litharge, lead tetroxide, and lead nitrate) on the synthesis were investigated. The influence of different catalyst loading approaches on the electrochemical reduction were also examined. The structure and surface morphology of the catalysts were characterized by X-ray diffraction and scanning electron microscopy. Catalyst activity was examined by dynamic potential analyses and cyclic voltammetry. Litharge was found to induce the greatest improvement in the electrolysis reaction rate and also decreases the reaction time. Coating the catalyst on the cathode helps enhance the product yield. The possible reaction mechanism was studied, and the catalyst was found to play a key role in transforming raw substances into intermediates. However, there is little effect on intermediate product transformation into the desired product. [Copyright &y& Elsevier]

Male F344 rats were exposed to hydrazobenzene (HZB) by dietary feed at concentrations of 0, 5, 20, 80, 200, or 300 ppm for 5 days, 2 weeks, 4 weeks, or 13 weeks duration. End points evaluated included clinical observations, body weights, liver weights, serum chemistry, blood HZB, gross pathology, and liver histopathology. There were no HZB exposure-related clinical signs of toxicity. During study weeks 8 through 13, body weight means in rats of the 300 ppm group were 6% lower compared to control rat means. Serum alkaline phosphatase concentrations were decreased in rats of the 300 ppm group at all time points. Relative (to body weight) liver weight increases were observed in rats of the 200 and 300 ppm groups following 5 days (300 ppm only), 2 weeks, 4 weeks, and 13 weeks of exposure. Following 13 weeks of exposure, microscopic findings in the liver were observed only in rats of the 200 and 300 ppm groups and consisted of hypertrophy, macrovesiculation, eosinophilic granular cytoplasm, and bile duct duplication. Blood HZB concentrations ranged from 0.002 to 0.006 µg/mL in rats of the 200 or 300 ppm groups. A no observed effect level of 80 ppm (4.80 mg/kg per d) was selected based on the observation of microscopic hepatocyte alterations at ≥200 ppm HZB. [ABSTRACT FROM AUTHOR]

In this study, two hydrazine derivatives, azobenzene and hydrazobenzene, were compressed in a diamond anvil cell at room temperature up to 28 GPa followed by decompression. In situ Raman spectroscopy was employed to monitor the pressure-induced structural evolutions. Azobenzene was found to undergo a phase transition at ∼10 GPa. Further compression to 18 GPa resulted in an irreversible breakdown of the molecular structure. Although hydrazobenzene exhibited a structural transition at a similar pressure of 10 GPa, it was found to sustain a compression pressure as high as 28 GPa without chemical reactions. The transition sequence of hydrazobenzene upon compression and decompression was thus entirely reversible in the pressure region studied, in strong contrast to that of azobenzene. The high-pressure structures of these two molecules were examined based on the spectroscopic data, and their drastically different high-pressure behaviors were analyzed and interpreted with the aid of ab initiomolecular orbital calculations. [ABSTRACT FROM AUTHOR]

The reactivity of tantalum dimethyl and diphenyl complexes (ONOcat)TaMe2(2) and (ONOcat)TaPh2(3) with aryl azides and 1,2-diphenylhydrazine is reported. p-Tolyl azide inserts into a Ta–C bond of 2or 3to afford (ONOcat)TaMe(η2-MeNNN-p-C6H4Me) (6) or (ONOcat)TaPh(η2-PhNNN-p-C6H4Me) (7), respectively. In the presence of another 1 equiv of azide, another insertion occurs, affording the bis(triazenido) complexes (ONOcat)Ta(η2-MeNNN-p-C6H4Me)2(4) and (ONOcat)Ta(η2-PhNNN-p-C6H4Me)2(5). Complexes 2and 3also react with 1,2-diphenylhydrazine, resulting in the loss of 2 equiv of methane or benzene, respectively, along with 1/2equiv of azobenzene. The tantalum-containing product was isolated as the pyridine adduct {(ONOcat)Ta(μ2-NPh)(py)}2(8), which implicates a tantalum(III) intermediate. The viability of this (ONOcat)TaIIIintermediate was proven by KC8reduction of (ONOcat)TaCl2(1) in THF, resulting in activation of a C–O bond of THF and formation of {(ONOcat)Ta(μ-O(CH2)3CH2)}2(10), which was characterized by single-crystal X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

Three silicon centered spirocyclic compounds 1-3, possessing silicon fused six- and five-membered rings have been prepared by the reaction of NHSi (L) [L = CH{(C=CH2)(CMe)(2,6-iPr2C6H3N)2}Si] with benzoylpyridine, diisopropyl azodicarboxylate, and 1,2-diphenylhydrazine, respectively, in a 1:1 ratio. The three spirocyclic compounds (1- 3) were obtained by three different pathways. The reaction of L with benzoylpyridine leads to the activation of the pyridine ring, and dearomatization occurred. Treatment of diisopropyl azodicarboxylate with L favors a [1 + 4]- rather than a [1 + 2]-cycloaddition product, and the azo compound was converted to hydrazone derivative. Finally the reaction of 1,2-diphenylhydrazine and L results in the elimination of hydrogen by activating one of the C-H bonds present in the phenyl ring. All three complexes 1- 3 were characterized by single crystal X-ray structural analysis, NMR spectroscopy, EI-MS spectrometry, and elemental analysis. In addition the optimized structures of probable products and possible intermediates were investigated using density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Abstract: 1,2-Bis(2,4,6-trinitrophenyl) hydrazine (3) is one of the precursors in the synthesis of an important energetic material viz., hexanitrazobenzene. The simple and convenient lab scale synthesis of title compound (3) was carried out by the condensation of picryl chloride (2) with hydrazine hydrate at 30–50°C in methanol based on the lines of scanty literature reports. Picryl chloride was synthesized by the reaction of picric acid (1) with phosphorous oxychloride based on the lines of reported method. The synthesized compound (3) was characterized by IR and 1H NMR spectral data. Some of the energetic properties of the synthesized compound have also been studied. The theoretically computed energetic properties of the title compound (3) indicated the superior performance in comparison to tetranitrodibenzo tetraazapentalene (TACOT) and hexanitrostilbene (HNS) in terms of velocity of detonation. [Copyright &y& Elsevier]

Abstract: Thin films of organic pigments were prepared at higher than pH 1 by the contact plating method using an anionic surfactant (AZNa, first figure of this article (part c) (n =4)) containing an azobenzene moiety. The effects of hydrophilic group of the surfactants on the rate of following reaction of the reduction product were studied by cyclic voltammetry. The positive shift of the reduction peak potential of AZNa compared to those of cationic and non-ionic surfactants was ascribed to higher rate of following reaction of reduction product due to the presence of the anionic hydrophilic group of the surfactant. The present investigation revealed that the anionic hydrophilic group accelerates the cleavage of the h name="dbnd" />Nthe azobenzene group. This phenomenon enabled us to prepare the organic thin film at higher pH condition. [Copyright &y& Elsevier]

Abstract: Pd/C catalysts doped with cerium oxide and iron oxide nanoparticles were prepared by thermal decarboxylation in the presence of cetylsulfonyl acetate, and used in the hydrogenation of o-chloronitrobenzene to give high yields of 2,2′-dichlorohydrazobenzene. It was found that the stability and activity of the Pd/C catalysts were significantly affected by doping with the nanosized metal oxides. The chemical structure of 2,2′-dichlorohydrazobenzene was confirmed by 1H and 13C NMR spectroscopy. [Copyright &y& Elsevier]

Abstract: Hydrogenation of azo bonds with hydrazine, mono-substituted hydrazine, and hydrazobenzene was studied with selected diazene compounds under oxygen-free conditions. The reactions proceed rapidly and in high yield in several solvents, utilizing all N–H protons. While the reduction process is accompanied by the evolution of nitrogen gas in the case of N2H4, the intermediacy of diimide could not be confirmed by standard trapping experiments. [Copyright &y& Elsevier]

Discusses the mechanism of formation of hydrogen trioxide in the ozonation of 1,2-diphenylhydrazine and 1,2-dimethylhydrazine. Initiation of ozonation by the formation of an ozone-hydrazine complex; Evidence showing that radical recombination can lead to a hydrazine hydrotrioxide which decomposes quickly even at low temperatures.

Describes the semiconductor-mediated photocatalyzed degradation of two selected priority organic pollutants, benzidine and 1,2-diphenylhydrazine in aqueous suspension. Degradation kinetics studied under different conditions such as reaction pH, substrate and photocatalyst concentration; Degradation rates and photonic efficiencies found to be strongly influenced by several parameters.

The values of isotropic HFS constants a were obtained for nitroxyl radicals (NR) of the piperidine series in hexane and water. The interrelation between rate constants for NR reduction and oxidation reactions, isotropic HFS constants a, inductive constants σ″ of the piperidine substituents, and electrochemical characteristics of NR were found. The dependence of the rate constants for the reduction of NR by hydrazobenzene (HB) and its oxidation by tetranitromethane (TNM) upon the Hammett type inductive constants σ, obtained using HFS constants a as the basis, was analyzed. The solvent effect on the reduction and oxidation reaction rate constants, the kinetic isotopic effect of the reduction reaction for a number of NR-HB systems, and alternative reaction mechanisms are considered. [ABSTRACT FROM AUTHOR]

Mn4(μ-NHPh)4(μ-PhNNPh-κ²N,N')2(py)4 (3) is synthesized via self assembly from dimeric Mn2(μ-NHPh)2(NR2)2 and PhNHNHPh (R = SiMe3). This cluster represents the N-N cleaved version of the previouslyreported Mn4(μ-NHPh)2(μ3-PhNNPh-κ³N,N')2(μ-PhNNPh-κ²N,N')(py)4 ''pinned butterfly'' cluster (2), formally reduced by two hydrogen atoms. Cluster 2 may be converted to 3 by addition of N,N'-diphenylhydrazine as a two-electron reductant. [ABSTRACT FROM AUTHOR]

The first general synthetic approach to 1,1′-bisindoles is described. Two simultaneous, ambient temperature Mori–Ban reactions were used to effect bisindolization of several diallylated hydrazobenzenes with minimal cleavage of the N–N bond. [ABSTRACT FROM AUTHOR]

An increase is found in the reactivity of organomercury and organothallium nitroxyl mono- and biradicals of the imidazoline type in comparison with the analogous compounds without organometallic fragments. This is explained by the formation of coordination bonds N→Hg, N→Tl, and N→O→Hg. [ABSTRACT FROM AUTHOR]

• Efficient and controllable synthesis of azobenzene and hydrazobenzene in one pot. • LSPR of Au NPs enhances the catalytic performance on the nitrobenzene hydrogenation. • TOF of nitrobenzene reduction is up to 404 h−1. • The Au–H species play a key role as important intermediate in hydrogenation step. The selective reduction of nitroaromatics has long been the focus of fundamental and practical interest. The challenging issue lies in how to finely control the product selectivity. Herein, we report a light-assisted thermocatalytical process to convert nitrobenzene into azobenzene and hydrazobenzene with high selectivity and high yields by simply controlling the reaction time. The light-enhanced efficiency of Au/TiO 2 catalyst is up to 14.8% at 90 °C due to the localized surface plasmon resonance (LSPR) effect of Au nanoparticles. Moreover, the hydrogen-delivery rate here is much faster than that of current reported systems. The reaction mechanism was also investigated by EPR technique, where Au–H intermediate species is found to account for the high efficiency in this reduction process. The favorable results demonstrated that plasmon-enhanced catalytic reaction might be more attractive and applicable in industrial organic synthesis. [ABSTRACT FROM AUTHOR]

A graphical abstract of the study "The 4.4'-Benzidine Rearrangement of 4-Alkyl Substituted Hydrazobenzenes" by M. E. Bouillon is presented.

The article describes a type of catalyst for the two-electron disproportionation of a zirconium(IV) redox-active ligand complex with 1,2-diphenylhydrazine to azobenzene and aniline. According to the authors, the metal catalysts relie on two-electron valence changes that occur at a redox-active ligand rather than at the metal center. They add that a two-electron oxidized [N2O2ox]Zr-imido species is implicated as an intermediate in the disproportionation reaction.