Novel heteropolycyclic nitrogen systems as pyrazoles, phthalazines and 1,2,4-triazines bearing a thiazolopyrazole moiety (4-11) have been synthesized via heterocyclization of 2-hydrazino-thiazolo [5,4-d]pyrazole (3) with α,β-bifunctional compounds under different conditions. Structures of the new products established by their elemental analysis and spectral data. Some of these products exhibit moderate-good antibacterial activity towards E. coli and S. aureus in compare with streptomycin and tetracycline antibiotic.