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Electron transfer processes in a series of pyrazole-2-in-5-ones (“pyrazolones-5”) and some of their thioanalogues are studied experimentally and theoretically for the first time. The electrochemical behavior of thiopyrazolones and oxygen analogues is found to differ. The effect the nature of the electrode, heteroatom, and substituents exerts on the redox potentials is established. Schemes of redox processes for the compounds studied in nonaqueous media are suggested. The schemes take account the ability of pyrazolones-5 to autoprotonation. Electrooxidation of 1-phenyl-3-methyl-4-benzoylpyrazole-2-in-5-one and its thioanalogues is shown to occur similarly to electroless oxidation with the formation of various dimers. It is established that, in the absence of active substituents during the electroreduction of compounds under study, the reaction center is the pyrazolone cycle, whose reduction does not involve decomposition of heterocyclic system.

Cyclic voltammetry and electrolysis in combination with ESR were used to study the electro- chemical oxidation of 1-R-4-hydroxyimino-3-methyl-2-pyrazolin-5-ones (R = H, C6H5, 4-BrC6H4, and 2-NO2-4-CF3C6H3) in acetonitrile on the background of 0.1 M Et4NClO4on glassy carbon and platinum electrodes in the absence and in the presence of bases (pyridine, piperidine, tetraethylammonium hydroxide). With all the compounds, one-electron transfer gives rise to iminoxyl radicals (g2.0045, aN630.78-31.33, aN11.87- 2.12). In alkaline medium the iminoxyl radical derived from 4-hydroxyimino-3-methyl-2-pyrazolin-5-one is unstable and oxidizes to 3-methyl-4-nitroso-1-pyrazolin-5-one. The oxidation potentials are much reduced with decreasing electron-acceptor power of the substituents and increasing basicity of the bases.

New 1,2-diacyl-1-arylhydrazines, containing a hydroxy group or a mobile halogen atom in the 1-acyl fragment, were obtained by the reaction of the arylhydrazones of acetyl and benzoyl chlorides with the salts of 2-hydroxy-, 2-acetoxy-, and 2-halogeno-3-nitrobenzoic acids. 1-(2-Hydroxybenzoyl)-1-aryl-2-acylhydrazines could not be converted into cyclic products. On heating in alkaline and acidic media elimination of the more hindered salicyloyl group and not dehydration occurred. When boiled in DMF in the presence of bases, 1-(2-halogeno-3-nitro-5-R-benzoyl)-1-aryl-2-acylhydrazines gave 2-aryl-5-R-7-nitroindazol-3-ones and not the expected 4,5-dihydrobenzo[f]-1,3,4-oxadiazepin-5-ones.

1.Oxidation of the arylhydrazones of the acetylhalides by PbO2 leads to the formation of 1,3,4,6-tetraaryl-1,4-dihydro-1,2,4,5-tetrazines, which, in turn, form stable cation-radicals under electrochemical oxidation.2.The stability of the dihydrotetrazine cation-radicals can be reduced, either by replacing the phenyl group at the nitrogen atom with a tosyl group or a hydrogen atom, or by replacing the phenyl groups at the carbon atoms with acetyl groups.3.Substituents at the amine N atom are more influential than substituents at the C atoms in fixing the first wave potential for the electrochemical oxidation of 1,4-dihydro-1,2,4,5-tetrazine.

It has been found that the final stage in the growth of an epitaxial film is decoration of the surface; to obtain objective information on the growth relief, it is necessary to examine at least two successive carbon replicas.

Three-component condensation of diethyl 2,4,6-trioxoheptanedicarboxylate with salicylaldehyde and ammonium acetate in EtOH affords 2,5-diethoxycarbonyl-5-hydroxy-4-oxo-4,4a, 5,10b-tetrahydro-1H-[1]benzopyrano[4,3-b]pyridine.

When the 2,4-dinitrophenylhydrazones of acetone, diethyl ketone, and cyclohexanone are treated with Br2 in AcOH, they are converted to the corresponding perbromides, which possess fungicidal and bacteriostatic properties.

1.Employing classical and cyclic polarography, and polarography with a Kalousek switch, a study was made of the electrochemical reduction of some phenyl-substituted arhylhydrazones of methylglyoxal, diketobutyric acid and its ethyl ester in dimethylformamide.2.The nitro derivatives of the arylhydrazones form the most stable anion-radicals.3.It is postulated that an intramolecular hydrogen bond is present in theo-nitro-substituted arylhydrazones, which is formed by the hydrazone proton and the nitro group.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.