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The condensation of thiosemicarbazones with bromopyruvic acid gives thiazolylhydrazone hydrobromides, which were converted to the free bases. The question of the site of protonation was studied by PMR spectroscopy. The possibility of self-protonation in 4-carboxythiazolylhydrazone crystals is not excluded. The thiazolylhydrazones are brominated in the 5 position. Both cyclization to thiazolyltriazoles and the Chetteueya—Walker reaction are realized in the case of oxidation with lead tetraacetate.

The condensation of dichloromethyl tert-butyl ketone (1) with benzaldehyde, para-bromobenzaldehyde, and 2,4-dichlorobenzaldehyde under conditions for the Darzens reaction gives 1-aryl-1-chloro-4,4-dimethyl-2,3-pentanediones (2–4). In the case of nitrobenzaldehydes, the reaction products are 1-aryl-2-chloro-1,2-epoxy-4,4-dimethylpentanones (5 and 6), which isomerize to α-chloroketones (7 and 8) upon prolonged storage or heating at reflux in benzene.

The products of condensation of 2-H-phthalazone hydrazones with carbonyl compounds in solution and in the crystalline form have phthalazone ylidenehydrazone (unsymmetrical azine) rather than phthalazinylhydrazone I structures, as has previously been assumed. 2-H-Phthalazone arylidenehydrazones exist in the EE′ form, and their analogs methylated in the 2-N position of the phthalazone ring exist in the ZE' form. Facile ZE' → ZZ' isomerization was noted for 2-methyl-4-chlorophthalazone ethylenehydrazone in halogen-containing solvents. Its unmethylated analog — 4-chlorophthalazone ethylenehydrazone (VIIIb) — is a mixture of geometrical isomers (EE'/EZ'=3∶1).

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.

1. The basicity constants of substituted benzaldehyde (BDMH) and acetophenone (ADMH) dimethylhydrazones in anhydrous acetonitrile are determined. 2. The amine nitrogen atom is the center of protonation in the dimethylhydrazones. 3. The effect of the substituents in the benzene ring on the reaction center is weakened 1.6-fold in the acoplanar ADMH molecules as compared to the BDMH molecules.

An increase in the resistance of the N-N bond to hydrogenolysis on Raney nickel in alkaline media is observed not only for 1,2,4-trisubstituted 3,5-dioxopyrazolidines but also for other types of 3,5-dioxopyrazolidines that are capable of enolization. 3,5-Dioxopyrazolidines that are capable of forming betaines also do not undergo hydrogenation in neutral ethanol. The use of the potentiometric method of Sokol'skii and Druz′ made it possible to establish very slight adsorption of the enolates and betaines on the catalyst surface. The decrease in adsorbability is explained by a decrease in the effective charges on the nitrogen atom of the heteroring; this is in agreement with the results of calculations of the enolate and enol by the Pariser-Parr-Pople method. An assumption regarding the greater aromatic character of the enolate as compared with the enol is expressed on the basis of a comparison of the bond lengths.

1. Electrochemical reduction of arylhydrazones of aromatic aldehydes begins with fragmentation at the N-N bond, whereas in the case of acylhdyrazones saturation of the azomethine bond precedes the fragmentation. 2. The contrast in the electroreduction of these types of hydrazones is determined by the difference in character of the lowest free MO of the hydrazone fragment; in acylhydrazones in contrast to arylhydrazones the orbital of the unshared pair of the amine nitrogen atom does not participate in the formation of this orbital.

1. It is shown that a number of aryl and acylhydrazones can be electrochemically carboxylated in non-aqueous media (acetonitrile, DMF) to give α-hydrazino (or hydrazido) acids. 2. On passing from benzoyl to acetylhydrazones electrocarboxylation no longer occurs, probably because of the predominance in the acetylhydrazones of the EE′E″ form, in which the basicity of the imino nitrogen atom is lower than in the EE′Z″ form.

1. p-Nitrobenzaldehyde thiosemicarbazone and semicarbazone have quinonoid structures in an alkaline medium, and p-dimethylaminobenzaldehyde derivatives have quinonoid structures in an acid medium. 2. A study was made of the effect of S-methylation on the ultraviolet spectra of the thiosemicarbazones of benzaldehyde, acetophenone, cyclohexanone, and acetone. 3. It was shown that there is a hypsochromic shift of the absorption maximum as we pass to a polar solvent for some thiosemicarbazones and their S-methyl derivatives.

The rate of hydrogenolysis of 3,5-dioxopyrazolidines at the N-N bond is determined by the number, position, and nature of the substituents in the heteroring. The introduction of a phenyl group into the 1 and 2 positions increases the rate of hydrogenation, while a phenyl group in the 4 position lowers it. On the other hand, an alkyl substituent in the 1 and 2 positions lowers the rate of hydrogenation, while an alkyl substituent in the 4 position increases it. It is assumed that the effect of substituents is a consequence of an increase or decrease in the adsorption of a molecule by the β-dicarbonyl or hydrazine fragments; this is in agreement with the results of calculation of the charges on the heteroring atoms. The hydrogenation of 4alkyl-1, 2-diphenyl-3,5-dioxopyrazolidines is limited by their activation, while the hydrogenation of the 4-phenyl derivative is limited by the activation of hydrogen.

By means of polarographic and microcoulometric methods it was shown that the reduction of semi- and thiosemicarbazones of acetophenone, p-chloroacetophenone and p-aminoacetophenone and also benzophenone semicarbazone at a dropping mercury electrode takes place irreversibly with participation of two electrons.

Die Azine (I) (analog auch entsprechende Hydrazone) reagieren mit den Diazoniumchloriden (II) in Eisessig bei 3-5°C zu den Hydrazonen (III); diese Hydrazone entstehen auch bei Einsatz von Gemischen entsprechender Aldehyde mit Hydrazinhy drat an Stelle des Azins (I).

Durch Umsetzung des Aminotriazols (I) mit einer Reihe aromatischer Aldehyde (II) wurden die Verbindungen (III) und ihre quartaren Salze (IV) dargestellt und ihre UV-Spektren in Athanol und in konzentrierter Schwefelsaure untersucht.

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.