Electrophilic and nucleophilic substitution in oxazolo[3,2-f]xanthines

Bromination of 2-aryloxazolo[3,2-flxanthines gives the 3-bromoderivatives whereas 8-methyl-2-phenyloxazolo[3,2-f]xanthine is nitrated in the para-position of the phenyl substituent. Alkylation of oxazolo[3,2-f]xanthines by ethylmonoiodoacetate gives the ethyl esters of oxazolo[3,2-f]xanthinyl-6-acetic acids. Reaction of oxazolo[3,2-f]xanthines with sodium sulfide gives thiazolo[3,2-f]xanthines whereas the reaction with secondary amines opens the oxazole ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1396–1399, October, 1990.     

Synthesis and transformations of 3-azido-5-amino-1,2,4-triazines

The reaction of the tetrazolediazonium ion with malonic acid dinitrile and nitroacetonitrile leads to the formation of 3-azido-5-amino-1,2,4-triazine derivatives. According to the mass-spectrometric data and the results of X-ray diffraction analysis, the crystalline compounds exist in the amino form. The facile hydrolysis of the amino and azido groups to azauracils is an argument in favor of the existence of the imino form in solution.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 557–561, April, 1984.     

Synthesis and properties of derivatives of 7-aroylalkylxanthinyl-8-thioacetic acid

When 7-aroylalkyl-8-bromo-3-methyl- and 1,3-dimethylxanthines are boiled with an excess of thioglycolic acid, a reductive dehalogenation takes place, while reaction with an equimolar amount of thioglycolic acid in DMFA leads to 7-aroylalkyl-3-methyl- and 1,3-dimethylxanthinyl-8-thioacetic acids. Cyclization of the latter with acetic anhydride in the presence of anhydrous sodium acetate results in the formation of 3-aryl-1,4-dihydro-9-methyl- and-7,9-dimethylthiazino[3,2-f]xanthine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 967–970, July, 1990.     

Ionization potentials of dipyridyls and diquinolyls

The ionization potentials of a number of isomeric dipyridyls and diquinolyls were determined. The differences in their values make it possible to establish the site of fusion of the rings in the 2,2, 3,3, and 4,4 positions of the system. The absence of an appearance potential for the fragment ion, the existence of which is due to cleavage of the interannular bond in the doubled hetaryl compounds, constitutes evidence for its double-bond character.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 812–814, June, 1976.     

Quaternary salts of quinolybenzimidazoles

The nitrogen atoms of the benzimidazole ring are alkylated initially in the quaternization of 2-(2-quinolyl)benzimidazole, and the nitrogen atom of the quinoline ring is alkylated only after this. Pyridyl- and quinolylbenzimidazoles and their quaternary salts were synthesized in order to study geometrical isomerism in the dihetaryl series. It was concluded that geometrical isomerism cannot occur in the case of the protonated forms or any other quaternary salts of dihetaryls, since as a result of the mutual electron-acceptor effect of the heteroaromatic cations the carbon-carbon bond between them is converted to a single bond, despite the fact that it is a bond between two sp² carbon atoms.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1662–1669, December, 1980.     

Naphthyridines in hetarylation reactions

The reaction of indole (2-methylindole) with 1,5-, 1,6-, and 1,8-naphthyridines at 20C, in the presence of benzoyl chloride, leads to the preferential formation of dihydro structures with one indolyl substituent at the -position to the hetero atom. With increase in temperature, dibenzoyl and monobenzoyl tetrahydro-substituted naphthyridines with two indolyl residues in both pyridine rings are formed besides the above compounds.Preliminary communication, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1218–1222, September, 1986.