From synthesis perspective, heterocycles with azido-azomethine structural entity are interesting due to the present 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/or temperature. Thus, azide-tetrazole ring-chain tautomerism is known to influence SNAr reactivity and regioselectivity. Also, nitrogen-rich heterocycles embody explosive properties as the nitrogen balance rises above 70% with the help of multiple azido group installation. Moreover, nitrogen-rich compounds are currently the most promising candidates for the next-generation “green” explosives. Herein, we present synthesis method toward fused tricyclic tetrazolopyridopyrimidines. We discovered that fused 2,4-diazidopyrimidines undergoe azide-tetrazole equilibrium which directs SNAr to take place at the C-5 position displacing residual azide as a leaving group. FT-IR and X ray analysis reveals tetrazole to be the major tautomeric form present in the solid state. On the other hand, the equilibrium in solution phase liberates azido group that can be further functionalized in for characteristic reactions of azido functional group. Calculated thermodynamic heats of tautomerization in solutions via variable temperature NMR experiments and DFT calculations support the observed experimental results. Additionally, we have synthesized a binary C6N16 perazidopyrimido[5,4-d]pyrimidine and tested its explosive properties.