E. V. Shchegol’kov

Synthesis, analgesic and antipyretic activity of 2-(antipyrin-4-yl)hydrazones of 1,2,3-triketones and their derivatives

Abstract1,2,3-Triketone 2-(antipyrin-4-yl)hydrazones were synthesized via the azo-coupling reactions of 1,3-diketones with 2-(antipyrin-4-yl)diazonium chloride. The fluoroalkyl-containing hetarylhydrazone enters into cyclocondensation with hydrazines at the 1,3-dicarbonyl fragment to yield 3-tetrafluoroethyl derivatives of pyrazole. It was found that 1,2,3-triketone 2-(antipyrin-4-yl)hydrazones and N-(2-hydroxyethyl)-substituted pyrazole exhibit analgesic activity comparable with that of their structural analog analgin (metamizole sodium), but do not possess antipyretic properties. In contrast, N-phenyl-substituted pyrazole did not exhibit analgesic properties but produced a certain antipyretic effect four hours after pyrogenic administration. Fluoroalkyl-containing compounds are less toxic substances than nonfluorinated 2-(antipyrin-4-yl)hydrazone and analgin.

Synthesis of fluoroalkyl-containing 1,2,3-triketone 2-hetarylhydrazones and their reactions with hydrazines

Fluoroalkyl-containing 1,2,3-triketone 2-(2,3-dimethyl-5-oxo-1-phenyl-1,2-dihydropyrazol-4-yl)-, 2-(4-ethoxycarbonylpyrazol-3-yl)-, and 2-(1,2,4-triazol-3-yl)hydrazones were synthesized by the azo coupling reactions of fluorinated 1,3-diketones with the corresponding hetaryldiazonium chlorides. The hetarylhydrazones thus synthesized were subjected to cyclocondensation with hydrazines at the 1,3-dicarbonyl fragment to give 3-fluoroalkyl-4-hetarylazopyrazoles.

Geometric isomerism in the series of fluoroalkyl-containing 1,2,3-trione 2-arylhydrazones

According to the 1H, 13C, and 19F NMR data, fluoroalkyl-containing 1,2,3-trione 2-arylhydrazones in CDCl3 exist exclusively, while in (CD3)2CO preferentially, as isomers in which the acyl or aroyl group is involved in intramolecular hydrogen bond. The isomer structure was assigned on the basis of the chemical shifts of the carbonyl carbon atoms and fluorine atoms and carbon-fluorine spin-spin coupling constants JC-F. X-Ray diffraction data showed that 1,2,3-trione 2-arylhydrazones in crystal have the same structure as in CDCl3 solution. Quantum-chemical calculations were performed to rationalize predominant formation of 1,2,3-trione 2-arylhydrazone isomers with a free polyfluoroacyl group.

Synthesis and structure of 4-hydroxy-4-fluoroalkyl-1,4-dihydroimidazo[5,1-c][1,2,4]triazines

Azo coupling of fluorinated 1,3-diketones with 4-ethoxycarbonyl-1H-imidazole-5-diazonium chloride led to the formation of 4-hydroxy-4-polyfluoroalkyl-1,4-dihydroimidazo[5,1-c][1,2,4]triazines. According to the 1H and 19F NMR data, these compounds in solution give rise to ring-chain tautomerism via opening of the C4-N5 bond, which is especially characteristic of dihydroimidazotriazines with a polyfluoroalkyl substituent longer than trifluoromethyl group.

Synthesis and Tuberculostatic Activity of Some 1,2,4-Triazines

The antituberculosis activity of dihydrotriazolo[5,1-c][1,2,4]triazines, dihydropyrazolo[5,1-c][1,2,4]triazines, dihydroimidazolo[5,1-c][1,2,4]triazines, and dihydrotetrazolo[5,1-c][1,2,4]triazines was studied. A synthetic method for convenient synthons, 3-amino-1,2,4-triazines, was proposed. Their tuberculostatic activity was investigated.

Steric structure of alkyl 2-aryl(hetaryl)hydrazono-3-fluoroalkyl-3-oxopropionates

Steric structure of fluorinated 2-arylhydrazono-3-oxo esters was studied by 1H, 19F, and 13C NMR spectroscopy and X-ray analysis. It was found that these compounds in the crystalline state and in solutions in acetone-d6, DMSO-d6, and CDCl3 exist as Z isomers with the ester fragment involved in intramolecular hydrogen bond with the hydrazone NH proton. Exceptions are alkyl 2-arylhydrazono-4,4-difluoro-3-oxobutanoates which exist in acetone-d6 as mixtures of Z and E isomers, the former prevailing. Unlike fluorinated analogs, ethyl 2-(4-methylphenyl)hydrazono-3-oxobutanoate in crystal has the structure of E isomer in which intramolecular hydrogen bond is formed between the NH proton and acetyl carbonyl group. The same compound in acetone-d6, DMSO-d6, and CDCl3 gives rise to a mixture of Z and E isomers, the latter prevailing.

Fluorinated 2-amino-5-phenyl-1,3,4-thiadiazines: synthesis and structures

Fluorinated 2-amino-5-phenyl-1,3,4-thiadiazines were obtained for the first time. A study of their tautomeric structures revealed that trifluoromethyl-containing 1,3,4-thiadiazines exist as the 4H-tautomer in both solutions and the solid state, while their monofluoroaryl analogs exist as the 6H-tautomer.

Features of synthesis and structure of ethyl (2Z)-3-hydroxy-(2,3,4,5-tetrafluorophenyl)-propyl-2-enoate

The structure of key intermediates in the synthesis of fluoroquinolone antibiotics: diethyl (2,3,4,5-tetrafluorobenzoyl)malonate and ethyl (2Z)-3-hydroxy-(2,3,4,5-tetrafluorophenyl)prop-2-enoate was for first time studied using X-ray diffraction (XRD) and 1H, 19F NMR spectroscopy. In solution both the esters were shown to exist as a mixture of enol and ketone tautomeric forms with predominance of the latter. According to the XRD analysis, ethyl (2Z)-3-hydroxy-(2,3,4,5-tetrafluorophenyl)prop-2-enoate in the solid state exists entirely in the enol form.

Condensation of fluoroalkyl-containing 1,2,3-trione 2-arylhydrazones with methylamine

Fluoroalkyl-containing 1,2,3-trione 2-arylhydrazones react with methylamine in different ways, depending on the substrate structure. Arylhydrazones having a short fluoroalkyl substituent (RF = CF3, HCF2CF2) react at the carbonyl group adjacent to the nonfluorinated substituent to give 3-alkyl(aryl)-2-aryldiazenyl-3-methylamino-1-polyfluoroalkylprop-2-en-1-ones. Arylhydrazones with a long-chain fluoroalkyl group (RF = C3F7 and longer) and a bulky nonfluorinated group take up methylamine molecule at the carbonyl group linked to the fluorinated substituent, and the subsequent haloform reaction yields N-methyl-2-arylhydrazono-3-oxobutanamides. Both types of products are formed in reactions of methylamine with 1,2,3-triketone 2-arylhydrazones having a long fluoroalkyl group and methyl group at the other carbonyl group. Template condensation of fluoroalkyl-containing 1,2,3-trione 2-arylhydrazones with methylamine over Ni(II) template gives bis[3-alkyl(aryl)-1-polyfluoroalkyl-3-methylamino-2-aryldiazenylprop-2-en-1-onato-N,N′]-nickel(II), regardless of the size of the fluoroalkyl substituent. The same complexes and their copper analogs can be obtained by treatment of 3-alkyl(aryl)-2-aryldiazenyl-3-methylamino-1-polyfluoroalkylprop-2-en-1-ones with the corresponding metal salts.

Hydroxy- and alkoxymethylation of polyfluoroalkyl pyrazoles

A synthetic route to 1-hydroxy- and 1-alkoxymethyl-3-polyfluoroalkylpyrazoles via regioselective N-hydroxy- and alkoxymethylation of N-unsubstituted pyrazoles with paraformaldehyde has been proposed. The alkoxyalkylation of polyfluoroalkylpyrazoles proceeds in aqueous-alcohol medium, whereas hydroxymethylation requires anhydrous conditions.