Synthesis of 9-Aryl-6,6-dimethyl-5,6,7,9-tetrahydro-1,2,4-triazolo[5,1-b]quinazolin-8(4H)ones

The reaction of 3-amino-1,2,4-triazole with arylidene derivatives of dimedone and their potential synthetic equivalents leading to the formation of 9-aryl-6,6-dimethyl-5,6,7,9-tetrahydro-1,2,4-triazolo[5,1-b]quinazolin-8(4H)ones has been studied. The direction of heterocyclization has been established, and the possible mechanisms for the formation of the pyrimidine heterocycle have been analysed.     

Aryl-substituted 6,7-dihydropyrazolo[1,5-a]pyrimidine

We have studied the reaction of 5-amino-3-phenylpyrazole with chalcones which takes place with the formation of arylsubstituted forms of dihydropyrazolo[1,5-a]pyrimidine and have discussed a possible mechanism for the reaction. Dehydrogenation of the compounds prepared has been effected using N-bromosucciniimide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 962–965, July, 1988.     

Reactions of 2-aryl-4-arylidene-4<Emphasis Type="Italic">H</Emphasis>-oxazol-5-ones with 3-amino-1,2,4-triazole, 5-aminotetrazole,and 2-aminobenzimidazole

The reactions of 3-amino-1,2,4-triazole, 5-aminotetrazole, and 2-aminobenzimidazole with 2-aryl-4-arylidene-4H-oxazol-5-ones (azlactones) were studied. The electron-releasing properties of the azole ring were demonstrated to influence the reaction pathway of azlactones with aminoazoles. The structures of the resulting compounds were established by ¹H and ¹³C NMR spectroscopy using spin-spin decoupling and the nuclear Overhauser effect.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2730–2733, December, 2004.     

Effect of substituents at atoms of double bonds on the conformation of the 1,3-cyclohexadiene ring

The effect of alkyl substituents at atoms of double bonds on the conformation of the 1,3-cyclohexadiene ring was studied using a molecular-mechanics method. It was shown that the introduction of substituents results only in a change of the degree of ring puckering. It is concluded that there is equilibrium between flattening and unflattening factors, which then governs the constancy of the ring conformation.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 4, pp. 334–337, July–August, 1992.     

Imine-enamine tautomerism of dihydroazolopyrimidines. 3. 5-Aryl-substituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines

5-Aryl-substituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines were obtained by condensation of 3-amino-1,2,4-triazole with -dimethylaminopropiophenone hydrochlorides or crotophenone. The effect of steric and electronic factors on the position of the imine-enamine equilibrium in solutions of the synthesized substances is examined. 5-Phenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyriniidine was subjected to x-ray diffraction analysis.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1539–1544, November, 1991.     

Cycle mobility in 1,4-dihydropyridine and its monoalkyl and phenyl derivatives

The conformational mobility of the 1,4-dihydropyridine cycle has been studied by the molecular mechanics method. It was shown that the N(1) and C(4) atoms are displaced asymmetrically from the plane of the double bonds. The asymmetry is the result of conjugation between the nitrogen lone pair and the systems of the double bonds. The influence of alkyl and phenyl substituents at the carbon atoms on the equilibrium conformation and cycle mobility has been investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1217–1219, July, 1993.     

Effect of electronic interactions between double bonds on the conformational flexibility of 1,4-cyclohexadiene

The electronic structure of 1,4-cyclohexadiene for various angles between the double bond planes has been calculated by the AM1 method. The effects of through-bond and through-space interactions, which result in flattening and unflattening, respectively, are oppositely directed. These effects are specified for various bending angles. In addition to steric factors, electronic factors affect the conformational flexibility of 1,4-cyclohexadiene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1676–1677, September, 1994.     

Cascade cyclization reactions of 3,4,5-triamino-1,2,4-triazole with aromatic aldehydes and cycloalkanones

A three-component condensation of 3,4,5-triamino-1,2,4-triazole (1) with aromatic aldehydes 2a–f and dimedone (3) or cyclohexanone (8) afforded partially hydrogenated 9-aryl-[1,2,4]triazolo[5,1-b]quinazolin-8-ones. The structure of 2-amino-6,6-dimethyl-3-(4-nitrobenzylidene)amino-9-(4-nitrophenyl)-5,6,7,9-tetrahydro[1,2,4]triazolo[5,1-b]quinazolin-8-one (4e) was confirmed by X-ray diffraction data. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1178–1182, July, 2006.     

Reaction of thiosemicarbazide with n-cyanoguanidine: synthesis of 3,5-diamino-1-thiocarbamoyl-and 3,5-diamino-1-thiazol-2-yl-1,2,4-triazoles

The reaction of thiosemicarbazide with N-cyanoguanidine in an acidic medium afforded 3,5-diamino-1-thiocarbamoyl-1,2,4-triazole, whose condensation with α-halo ketones gave 3,5-diamino-1-thiazol-2-yl-1,2,4-triazoles 7a–d. The latter were also prepared by the independent synthesis from 2-hydrazinothiazoles and N-cyanoguanidine. Acylation of compounds 7a,d under mild conditions and their condensation with aldehydes occur at the C(3′)NH₂group. The structure of aroyl derivative 11c was established by X-ray diffraction. Acylation of diaminothiazolyltriazole 7a in boiling Ac₂O afforded 3,5-diacetylamino-1-(4-phenylthiazol-2-yl)-1,2,4-triazole. Hydrogenation of arylidene derivatives 14b,c and aroyl derivative 11c gave the corresponding benzylaminotriazoles 15a,b. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 329–334, February, 2006.     

Synthesis, Structure, and Some Properties of Substituted 3-Carbethoxy(methoxy)-5-cyano-1,2,3,4-tetrahydrospirocyclohexane-4-pyridine-2-thiones

The condensation of cyclohexylidenemalononitrile or cyclohexylidenecyanoacetic ester with thioamidoethyl(methyl)malonate in the presence of sodium ethylate gave 6-amino-3-carbethoxy-5-cyano-4-spirocyclohexane-1,2,3,4-tetrahydropyridine-2-thione and 3-carbethoxy(methoxy)-5-cyano-6-oxo-4-spirocyclohexanepiperidine-2-thiones which were used in the synthesis of the corresponding substituted 2-alkylthiotetrahydropyridines. 5-Carbethoxy-3-cyano-3-methyl-6-methylthio-4-spiro-cyclohexane-3,4-dihydropyridine-2(1H)-one was studied by X-ray crystallography.