Catalyst-free synthesis of various derivatives of a novel heterocyclic system of 3-alkyl-9-methyl-tetrazolo[1,5-a][1,2,3]triazolo[4,5-d]pyrimidine

Azolo-annulated pyrimidines have attracted continuing interest due primarily to their structural similarity to heterocyclic bases of DNA and RNA. As a consequence, these compounds can act as antimetabolites, being effective biologically active compounds. Numerous advantageous properties of azolopyrimidines such as important industrial, agrochemical and pharmaceutical applications, especially in biological science, material chemistry and medicinal chemistry impelled us to design and synthesis of a number of various and interesting derivatives of 3-alkyl-9-methyl-tetrazolo[1,5-a][1,2,3]triazolo[4,5-d]pyrimidine as a novel heterocyclic system which has not been reported previously. In the present work, initially the reaction of 2,4-dichloro-6-methylpyrimidin-5-amine (1) with different primary amines in refluxing i-PrOH gave the corresponding sec-amino derivatives (2a-e) which were consequently treated with NaNO2/HCl solution to yield quantitatively the corresponding diazo derivatives of 5-chloro-3-alkyl-7-methyl-3H-[1,2,3]triazolo[4,5-d]pyrimidine (3a-e). Further reaction of compounds (3a-e) with NaN3 in EtOH was resulted in various derivatives of novel heterocyclic system of tetrazolo[1,5-a][1,2,3]triazolo[4,5-d]pyrimidine (4a-e) that are in equilibrium with azide forms.