Heterocycles with azido-azomethine structural entity undergo dynamic azide-tetrazole equilibrium in solution phase. The equilibrium can be shifted towards one or other tautomer by altering ambient conditions such as solvent polarity and temperature. Thus, azide-tetrazole ring-chain tautomerism is known to influence SNAr reactivity and regioselectivity. We have synthesized a new class of tetrazolopyridopyrimidines 3 and characterized their azido-azomethine - tetrazole tautomerism (Scheme 1). FT-IR and X-ray analysis of 3 reveals tetrazole to be the major tautomeric form present in the solid state. On the other hand, the equilibrium can be shifted in solution phase and the liberated azido group can be further functionalized in Huisgen cycloaddition reactions. Thermodynamic heats of tautomerization in solutions were calculated using variable temperature NMR and DFT.