S. M. Desenko

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.

Layered crystal structure of bicyclic aziridines as revealed by analysis of intermolecular interactions energy

An X-ray diffraction study of three bicyclic aziridines (2,2-dimethyl-4,6-diaryl-1,3-diazabicyclo-[3.1.0]hex-3-enes) reveals the absence of strong specific intermolecular interactions in the crystals. Therefore, crystal packing has been analyzed on the basis of quantum-chemical calculations of energy of intermolecular interactions between basic molecules located in the asymmetric part of the unit cell and molecules belonging to its first coordination sphere in the crystal. The analysis of the energy of intermolecular interactions indicates that the crystal structures of bicyclic aziridines are layered. The total energy of the interactions between the basic molecule and other molecules belonging to the layer is significantly higher as compared to the energy of the interactions with molecules of two neighbouring layers.

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.

Synthesis and Rotamerism of 9,10-Diarylsubstituted 1,2,3,4,5,6,7,8,9,10-Decahydroacridine-1,8-Diones

Condensation of aromatic aldehydes with 5,5-dimethylcylohexane-1,3-dione and primary arylamines gave 9,10-diaryl-3,3,6,6-tetramethyl-1,2,3,4,5,6,7,8,9,10-decahydroacridine-1,8-diones. Several stereochemical features of the synthesized compounds are discussed. Dynamic NMR was used to determine the inversion barriers for the rotamers formed.

Partially hydrogenated aromatic substituted tetrazolo[1,5-a]pyrimidines

By treating 5-aminotetrazole with aromatic α,β-unsaturated ketones or with Mannich base hydrochlorides there have been synthesized aromatic substituted 4,7-dihydrotetrazolo[1,5-a]-pyrimidines. They can be reduced to the corresponding 4,5,6,7-tetrahydro derivatives by the action of NaBH4. The high thermodynamic stability of the 4,7-dihydrotetrazolo[1,5-a]pyrimidines when compared with the 4,5-dihydro isomers has been revealed. Reaction of 5-aminotetrazole both with cyclohexanone as well as with 2-cyclohexylidenecyclohexanone leads to formation of 9,9-pentamethylene-4,5,6,7,8,9-hexahydrotetrazolo[5,1-b]quinazoline, the structure of which was demonstrated using X-ray crystallography.

Chemical conversions of 5,7-disubstituted dihydro-1,2,4-triazolo[1,5-a]pyrimidines

Hydrolysis, oxidation, reduction, alkylation, and nitrosation of aromatic-substituted dihydro-1,2,4-triazolo-[1,5-a]pyrimidines 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.

Reaction of arylidene derivatives of Meldrum's acid with 3-amino-1,2,4-triazole

The condensation of arylidene derivatives of Meldrums acid with 3-amino-1,2,4-triazole in nitrobenzene leads to 4,5,6,7-tetrahydro-1,2,4-triazolo [1,5-a]pyrimidin-5-ones. In DMF the reaction proceeds with the formation of arylsubstituted N-(2H-1,2,4-triazol-3-yl)-3-(2H-1,2,4-triazol-3-ylamino)propionamides.

Reactions of α-aminoazoles with diethyl benzylidenemalonate

Cyclocondensations of diethyl benzylidenemalonate with 3-amino-5-methylpyrazole, 3,5-diamino-1,2,4-triazole, 3,4,5-triamino-1,2,4-triazole, and 2-amino-benzimidazole in alcohols take a single route and lead to the formation of functionally substituted partially hydrogenated pyrazolo-, triazolo[1,5-a]-pyrimidin-5-ones and pyrimido[1,2-a]benzimidazol-2-one respectively. From reaction mixtures involving 3-amino-1,2,4-triazole and its 5-methylsulfanyl analog in methanol the intermediate products of heterocyclization were isolated forming as a result of alkylation with the β-carbon of the unsaturated ester the endocyclic nucleophilic sites of aminoazoles. The structure of one among the products obtained, diethyl(3-amino-5-methylsulfanyl-1,2,4-triazol-2-yl)benzylmalonate was proved by X-ray crystallography. In DMF the same reagents yielded mixtures of partially hydrogenated triazolo[1,5-a]pyrimidin-5-ones.

Synthesis and tautomerism of 5,7-diaryl-3-cyano-and 5,7-diaryl-3-ethoxycarbonyl-4,7(6,7)-dihydropyrazolo[1,5-a]pyrimidines

The cyclocondensation of 3-amino-4-cyanopyrazole and 3-amino-4-ethoxycarbonylpyrazole with 1,3-diaryl-2,3-propen-1-ones gives the corresponding 3-substituted 5,7-diaryl-4,7(6,7)-dihydropyrazolo[1,5-a]pyrimidines. Their tautomeric composition in solution has been investigated by 1H NMR.