Hydrazo Compounds Research Articles

Synthesis and photochemical properties of azidohemicyanine

Photochemical activity of azidohemicyanine (1-methyl-4-(4-azidostyryl)quinolinium iodide) was predicted by quantum chemical calculations and confirmed experimentally. The azidohemicyanine, which was synthesized, is characterized by a long-wavelength absorption band (LWAB) in the spectral region 350–500 nm with a maximum at 417 nm; it decomposes with a quantum yield of 0.84±0.17 upon irradiation within the LWAB, the quantum yield being independent of the presence of oxygen. The reaction products identified by ESI mass spectrometry include the corresponding primary amine as well as azo, hydrazo, nitroso, and nitro compounds, some of them are unidentified. The azidohemicyanine possesses the longest-wavelength visible light sensitivity among aromatic azides known so far.

Solvent‐Free Basic or KF/Alumina‐Assisted Dehydrogenation of Hydrazo Compounds.

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Catalytic Oxidation of Hydrazo Derivatives Promoted by a TiCl3/HBr System

Through a novel catalytic process of general synthetic interest, hydrazo compounds were efficiently and selectively converted into corresponding azo derivatives. The proposed mechanism of this process comprises two separate and distinctive catalytic cycles, linked together by radical species. The first cycle includes formation of a hydroxy radical, generated by Ti(III) single-electron reduction of H2O2. In the second cycle, the hydroxy radical oxidizes HBr into hypobromous acid, which in turn is reduced back to HBr and water by a hydrazo substrate.

Solvent-Free Basic or KF/Alumina-Assisted Dehydrogenation of Hydrazo Compounds

A reduction of organic solvents in the organic chemical industry is of serious importance for sustainable chemistry. With this viewpoint, we successfully established the useful dehydrogenation of hydrazo compounds using basic alumina or KF/alumina ­under solvent-free conditions to afford azo compounds in good to excellent yields.

Polarographic Behavior and Determination of 1,1-Dimethyl-3-phenyltriazene

Polarographic behavior of the genotoxic substance 1,1-dimethyl-3-phenyltriazene was investigated and optimum conditions were found for its determination by sampled direct current polarography and differential pulse polarography at a static mercury drop electrode in the concentration range from 1 × 10-4 to 1 × 10-7 mol l-1. It was established that for reduction of the triazene group four electrons are required resulting in the formation of amino and hydrazo compound. The resulting products were identified, and the reduction pathway was proposed.

Dehydrogenation of Unsymmetric Hydrazo Compounds in Ionic Liquid: Novel Green Synthesis of Azo Compounds

Using NBS (N-bromosuccinimide) and the ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) as an oxidation system, twelve unsymmetric azo compounds were efficiently prepared from hydrazo compounds for the first time. In contrast to the known methods, this novel access to azo compounds presented here is operationally simple, environmentally benign and has the advantage of enhanced atom utilization. Furthermore, the solvent and the basic catalyst used can be recovered conveniently and reused efficiently.

The oxidation kinetics of reduction intermediate product of methyl red with hydrogen peroxide

The reduction of methyl red and oxidation of intermediate product of its reduction in the presence of molecular oxygen and hydrogen peroxide in 0.2 mol L −1 HAc–NaAc buffer (pH 4.4) were studied at carbon paste electrode by voltammetry. The pseudo-reversible reduction of methyl red in red quinonoid form in a 2e −, 2H + addition ended to the colorless corresponding hydrazo compound without any following reaction. When dissolved oxygen or hydrogen peroxide were present, the intermediate product of methyl red reduction was oxidized to re-form the original. The apparent rate constant k f of the oxidation reaction of intermediate product by hydrogen peroxide was 744 mol −1 L s −1.

Facile Transfer Hydrogenation of Azo Compounds to Hydrazo Compounds and Anilines by Using Raney Nickel and Hydrazinium Monoformate

Azo compounds are conveniently reduced to either partially reduced hydrazo compounds or completely reduced anilines by employing Raney nickel in presence of hydrazinium monoformate depending upon reaction conditions. The other reducible moieties like ‒COOH and halogens are tolerated. The reduction process is selective, rapid and high yielding.

Graphical Abstracts

Synth. Commun. 2004, 34, 1 Facile Transfer Hydrogenation of Azo Compounds to Hydrazo Compounds and Anilines by Using Raney Nickel and Hydrazinium Monoformate H. S. Prasad, Shankare Gowda, and D. Channe Gowda* Department of Studies in Chemistry, University of Mysore, Mysore, Karnataka, India

Polarographic and voltammetric investigation of 8-hydroxy-7-(4-sulfo-1-naphthylazo)-5-quinoline sulfonic acid

The behaviour at HMDE and SMDE of 8-hydroxy-7-(4-sulfo-1-naphthylazo)-5-quinolinesulfonic acid has been studied by several techniques including Square wave voltammetry (SWV), Differential pulse plarography (DPP), Direct current polarography (DCP) and Cyclic voltammetry (CV). Current–potential curves recorded at HMDE and SMDE electrode provide information on electrode reaction mechanism. The reduction of a pre-protonated azo group involving a four-electron process and two peaks or waves, gives amine derivatives in acidic solutions. In alkaline solution the reduction process occurs at more negative potential with the formation of a stable hydrazo compound. The electrochemical reduction mechanism of the azo compound is suggested using SWV, DPP, DCP and CV techniques in aqueous solutions of varying pH.

Ammonium Chloride Mediated Reduction of Azo Compounds to Hydrazo Compounds.

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A Simple and Efficient Method for the Dehydrogenation of Symmetric Hydrazo Compounds with NaNO2—Ac2O.

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Facile Transfer Hydrogenation of Azo Compounds to Hydrazo Compounds and Anilines by Using Raney Nickel and Hydrazinium Monoformate.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Ammonium Chloride Mediated Reduction of Azo Compounds to Hydrazo Compounds

The reduction of azo compounds with magnesium powder as catalyst in the presence of ammonium chloride at room temperature in methanol leads to hydrazo compounds.

The mechanism and kinetics of the electrochemical cleavage of azo bond of 2-hydroxy-5-sulfophenyl-azo-benzoic acids

The electrochemical reduction of 2-hydroxy-5-[(4-sulfophenyl)azo]benzoic acid, 2-hydroxy-5-[(3-sulfophenyl)azo]benzoic acid, 2-hydroxy-5-[(2-sulfophenyl)azo]benzoic acid and 2-hydroxy-5-azo-benzoic acid has been carried out in aqueous solutions at glassy carbon electrode using cyclic voltammetry and chronoamperometry. The position of sulfo substituent relative to azo bridge as well as pH of the solution have significant impact on the electrochemical behavior of these compounds. It has been proposed that these compounds are reduced predominantly as hydrazone tautomers resulting in corresponding hydrazo compounds. The overall electrochemical reduction follows DISP2 mechanism, ultimately leading to the 5-amino salicylic acid and sulfanilic acid. The rate determining step is the homogenous redox reaction between intermediate hydrazo compound and 5-amino salicylic acid quinoneimine. The mechanism is proposed in which activated complex of 5-amino salicylic acid quinoneimine and intermediate hydrazo compound is formed with the simultaneous loss of one proton.

A Simple and Efficient Method for the Dehydrogenation of Symmetric Hydrazo Compounds with NaNO2/NaHSO4×H2O/SiO2.

Azo compounds have caused great interest in organic synthesis. They are widely used as dyes and analytical reagents. 1 Optical-switching and image storage can be made using azobenzene liquid crystal films. 2,3 Recently, many noteworthy studies have shown that some azo compounds possess excellent optical memory and photoelectric properties. 4,5 The oxidation of ArNHNHAr to azo compounds is an important transformation in organic synthesis. We have been paying particular and continuous attention to this field. In the previous work, NBS/pyridine 6 and FeCl3·6H2O 7 and galvinoxyl 8 have been used as effective reagents to synthesise azo benzene. These existing methods have their merits, but they also have drawbacks such as tedious operation and using a large amount of volatile and poisonous solvent, which affects human health and the environment. To continue our research on the synthesis of azo compounds, we decided to develop a new reagent system for the dehydrogenation of ArNHNHAr. The combination of sodium nitrite and sodium hydrogen sulfate in the presence of wet SiO2 has been used as an effective oxidising agent for the dehydrogenation of 4-substituted- 1,2,4-triazole-3,5-diones successfully. 9

Catalytic Transfer Hydrogenation of Azo Compounds to Hydrazo Compounds Using Inexpensive Commercial Zinc Dust and Hydrazinium Monoformate

Azo compounds are conveniently reduced to hydrazo compounds by using commercial zinc dust and hydrazinium monoformate at room temperature. Many reducible and hydrogenolysable groups like OCH3, OC2H5, OH, COOH, CH3, SO3Na and halogens are tolerated. The reduction is fast, clean, high‐yielding and inexpensive.

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.

Heterocyclic derivatives from natural occurring naphthoquinones: synthesis, characterization and X-ray structure of beta-lapachone hydrazo compounds

β-Lapachone-5-phenylhydrazone and β-lapachone-6-phenyl-hydrazone were synthesised and characterised using 1H and 13C NMR, IR, and UV–visible and X-ray analyses. 1H NMR and UV–visible spectroscopic data indicate that the hydrazo form dominates in solution. Similarly, X-ray crystallographic data indicated that the hydrazo form exists exclusively in the solid state.

Coulometric and spectroscopic investigations of the oxidation and reduction of some azosalicylic acids at glassy carbon electrodes

Constant potential coulometry in combination with cyclic voltammetry, UV–Vis, 1H and 13C NMR spectroscopy were used to identify the oxidation and reduction products for some structurally similar azosalicylic acids, including the azosalicylic drugs Sulfasalazine ® and Olsalazine ®. The experiments were carried out in aqueous solutions at pH 4.5 to 10.0. Voltammetric and UV–Vis spectroscopic comparisons involving standard substances confirm that all compounds studied, except 4,4′-azobis-[2-hydroxybenzoic acid], are reduced in an overall four-electron process to their corresponding amines. For 4,4′-azobis-[2-hydroxybenzoic acid], the reduction involves only two electrons and most likely gives rise to the corresponding hydrazo compound. The oxidations of 3,3′-azobis-[6-hydroxybenzoic acid] (Olsalazine ®), 3,3′-azoxybis-[6-hydroxybenzoic acid] and 2-hydroxy-5-[(3′-carboxy-2′-hydroxyphenyl)azo]benzoic acid were found to involve an initial two-electron step. Based on UV and NMR spectroscopic data, it is proposed that the oxidation of 3,3′-azobis-[6-hydroxybenzoic acid] gives rise to a 2,2′-dicarboxy-1,4-dibenzoquinone azine.