Recent publication describes hydrolytic cleavage of azole and azine condensed cycles under the action of nucleophiles [1,3,6, 4,9,11,12,15,17,20,25,26,28,29]. It is known that kinetics of the reactions mentioned depends on basic properties of nucleophilic reagents. Strong nucleophiles (hydroxides and alkoxides of alkaline metals, hydrazine hydrate) easily react with the given substrates in the water or alcohol-water medium for 1 h and form products with high yields [4,15,20,25,26,28,29]. Moreover, water may play the role of a nucleophile in hydrolytic cleavage reactions. In this case the reaction proceeds for 1 h and needs acidic catalysis [1,6]. It has been noted that cleavage of the pyridine cycle of 2-aryl-[1,2,4]triazolo[1,5-c]quinazoline is insufficiently known in spite of potentially bioactive products of this transformation. In addition, products of the reactions mentioned may take a worth place in the process of development of approaches for forming new heterocyclic systems and drug discovery [2,8,13,18,19, 23,24].Moreover, we found reports where the hypoglycemic activity of derivatives of 1,2,4-triazole were described. Thus, A.K.Mohammed Iqbal and co-authors discussed in their research the hypoglycemic and hypolipidemic action of novel compounds, which molecules contained the thiazolidone fragment attached to the triazole cycle via phenoxyethenthiol "linker" groups [14]. 4-Methyl-3-(R-phenyl-,1-methyl-1Н-indol-4(5)-yl)-5-(R-phenyl-)-4H-1,2,4-triazoles as selective inhibitors of 11β-hydroxysteroid dehydrogenase 1 were described as prospective glucose-lowering agents by Susan D. Aster and co-authors [7], and "ELI LILLY and COMPANY" applied for patent series of 2-R 1 -4-R 2 -5-alkaryl-(alkheteryl-, aryl-(heteryl-) oxy-, aryl-(heteryl-)thio-, aryl-(heteryl-)amino-)-2,4-dihydro-3H-1,2,4-triazol-3-ones(thiones) with high affinity to nuclear hormonal receptors. They may be used for treating diabetes, cardiovascular disorders, obesity, Xsyndrome and gastrointestinal disorders [21, 22], etc.Thus, the aims of the present research were to study the peculiarities of the given type of the reaction, elucidation of the effect of o-, m-, p-substituted aryl moiety in position 2 of [1,2,4]triazolo [1,5-c]quinazolines on the process of the pyrimidine cycle hydrolytic cleavage, as well as the hypoglycemic action of the compounds synthesized.experimental part 1. Chemistry 1.1. General method. Melting points were determined in open capillary tubes and were uncorrected. The ele-