Synthesis of some pyrazolo[3,4-d]pyrimidines and their fused triazole and tetrazole derivatives

Reaction of 2 with different reagents, namely formic acid, acetic anhydride and trichloroacetonitrile, yielded pyrazolo[3,4-d]pyrimidine derivatives 3, 5 and 6, respectively. Pyrazolo[3,4-d]pyrimidine m-thiazine(7) and 2,4-(1H,3H)dithione (8) derivatives were formed by the action of carbon disulfide on 2, depending on the reaction medium. Interaction of 7 with hydrazine hydrate yielded the aminoimino derivative 9 which reacted with acetic anhydride, triethyl orthoacetate and/or appropriate aldehydes to give 11, 12 and 13a,b, respectively. Methylation of compound 8 gave 14, which reacted with hydrazine hydrate to afford the monohydrazino derivative 15. Reaction of 15, with formic acid and nitrous acid afforded pyrazolo[4,3-e]triazolo[1,5-c]pyrimidine (16) and pyrazolo[4,3-e]tetrazolo-[1,5-c]pyrimidine (17) derivatives, respectively. The structures of products 3-17 were identified in light of their elemental analyses and spectra data.