M. G. Shirobokova

Synthesis of partially hydrogenated 1,2,4-triazoloquinazolines by condensation of 3,5-diamino-1,2,4-triazole with aromatic aldehydes and dimedone

Three-component condensation of 3,5-diamino-1,2,4-triazole with aromatic aldehydes and dimedone in dimethylformamide gives 2-amino-5-aryl-8,8-dimethyl-5,6,7,8,9,10-hexahydro[1,2,4]triazolo[3,2-b]quinazolin-6-ones. The reaction of 3,5-diamino-1,2,4-triazole with dimedone in the absence of aldehyde involves dimethylformamide as one of the carbonyl components to afford 2-amino-8,8-dimethyl-6,7,8,9-tetrahydro[1,2,4]triazolo[2,3-a]quinazolin-6-one.

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.

Cyclocondensation of 2-Aminobenzimidazole with Dimedone and Its Arylidene Derivatives

The reactions of 2-aminobenzimidazole with substituted benzaldehydes and dimedone, 2-arylidene derivatives of dimedone, 9-arylhexahydro-1H-xanthene-1,8(2H)-diones and also with dimedone and DMF have been studied. The direction of formation of the pyrimidine ring has been established and discussed. An X-ray structural investigation of 2,2-dimethyl-2,3-dihydrobenzimidazo[1,2-a]quinazolin-4(1H)-one has been carried out.

Cascade cyclization of 3(5)-aminopyrazoles with aromatic aldehydes and cyclohexanediones

Three-component condensation of 5(3)-amino-3(5)-methylpyrazole with aromatic aldehydes and 1,3-cyclohexanedione afforded mixtures of 3-methyl-4-aryl-2,4,6,7,8,9-hexa hydro-5H-pyrazolo[3,4-b]quinolin-5-ones and 2-methyl-9-aryl-5,6,7,9-tetrahydro pyrazolo[5,1-b]quinazolin-8(4H)-ones. The reaction of 3-aminopyrazolo-4-carbonitrile and ethyl 3-aminopyrazolo-4-carboxylate with aldehydes and cyclo hexanedione or dimedome is regioselective and leads to the formation of partially hydrogenated pyrazolo [5,1-b]quinazolin-8-one systems. In all compounds the dihydroazine ring exists in the enamine tautomeric form.

Synthesis of partially hydrogenated pyrazolo[3,4-b]quinolinones by condensation of 3-amino-5-methylpyrazole with aromatic aldehydes and dimedone

Cyclocondensation of 3-amino-5-methylpyrazole with 2-arylmethylidene-5,5-dimethylcyclohexane-1,3-diones or 9-aryl-3,3,6,6-tetramethyl-2,3,4,5,6,7,8,9-octahydro-1H-xanthene-1,8-diones, as well as with synthetic precursors of the latter (para-substituted benzaldehydes and dimedone), in dimethylformamide or methanol gives the corresponding 4-aryl-3,7,7-trimethyl-2,4,6,7,8,9-hexahydropyrazolo[3,4-b]quinolin-5-ones. The structure of 4-(4-methoxyphenyl)-3,7,7-trimethyl-2,4,6,7,8,9-hexahydropyrazolo[3,4-b]quinolin-5-one was proved by the X-ray diffraction data.

Chemical Reactions of 2-Methyl-5,7-diphenyl-6,7-dihydropyrazolo[1,5-a]pyrimidine

The hydrolysis, oxidation, reduction, alkylation, formylation, and nitrosation reactions of 2-methyl-5,7-diphenyl-6,7-dihydropyrazolo[1,5-a]pyrimidine have been studied.

Cyclocondensation of 3-Amino-1,2,4-triazoles with Esters of Substituted Cinnamic Acids and Aromatic Unsaturated Ketones

We have studied the reactions of 3-amino, 3,5-diamino-, and 3-amino-5-trifluoromethyl-1,2,4-triazole with esters of substituted cinnamic acids and aromatic unsaturated ketones; we have established the directionality of formation of the tetrahydrooxopyrimidine ring. We have carried out hydrolysis and hydrazinolysis of 7-phenyl-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidin-5-one. We have conducted an X-ray diffraction study of isopropylidene hydrazide of 3-(5-amino-1,2,4-triazol-1-yl)-3-phenylpropionic acid.

Multicomponent Reaction of 2-aminobenzimidazole, Arylglyoxals, and 1,3-cyclohexanedione

Three-component reactions of 2-aminobenzimidazole with arylglyoxals and 1,3-cyclohexanedione have been studied under conventional heating and microwave irradiation. Different product types including the Michael adduct and fused heterocyclic systems were obtained. Conditions for the selective formation of 12-aroylbenzimidazo[2,1-b]quinazolin-1(2H)-ones and 3-oxo-2-(2-aryl-1H-imidazo[1,2-a]-benzimidazol-9-ium-3-yl)cyclohex-1-enolates have been determined. The structures of all compound types were established by an X-ray diffraction study.

Heterocyclizations of 5-methylpyrazol-3-amine with unsaturated arylaliphatic carboxylic acid derivatives

Cyclocondensation of 5-methylpyrazol-3-amine with methyl cinnamate and arylmethylidenemalonic acids in DMF and methanol leads to the formation of 7-aryl-2-methyl-6,7-dihydropyrazolo[1,5-a]-pyrimidin-5(4H)-ones. Arylmethylidenemalonic acids react with the title amine at a ratio of 1:2 in nitrobenzene to give 4-aryl-3,5-dimethyl-1,7-dihydrodipyrazolo[3,4-b:4′,3′-e]pyridines. Heterocyclizations of 5-methylpyrazol-3-amine with 5-arylmethylidene-2,2-dimethyl-1,3-dioxane-4,6-diones or their precursors, para-substituted benzaldehydes and 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum’s acid) in all solvents (methanol, DMF, and nitrobenzene) give the corresponding 4-aryl-3-methyl-2,4,5,7-tetrahydropyrazolo[3,4-b]pyridin-6-ones. The structure of 3-methyl-4-(4-nitrophenyl)-2,4,5,7-tetrahydropyrazolo[3,4-b]pyridin-6-one was proved by X-ray analysis.

Interaction of aminoazoles with meldrum's acid and dialkyl ketones or cyclohexanone

Interaction of 3-amino-5-methylpyrazole, 3-amino-5-methylthio-, and 3,5-diamino-1,2,4-triazole with Meldrum’s acid, acetone, ethyl methyl ketone, and cyclohexanone leads to alkyl-substituted pyrazolo[3,4-b]pyridin-6-ones and 1,2,4-triazolo[1,5-a]pyrimidin-7-ones respectively. The structure of 5,5-dimethyl-2-methylthio-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidin-7-one was demonstrated by an X-ray structural investigation.