One-Pot Synthesis of Triazolo[5,5]-Fused Heterocycles via Heteroaryl Diazonium Salts

Triazolo-[5,5]-fused ring systems have attracted growing interest due to their diverse applications in biomedicine, agrochemicals, and, particularly, in energetic materials, owing to their rigid, nitrogen-rich architectures. However, efficient construction of these [5,5]-fused frameworks remains synthetically challenging, largely due to steric congestion and limited functional group compatibility. Here, we report a modular and operationally simple strategy involving the in situ generation of heteroaryl diazonium salts, followed by tandem nucleophilic addition and intramolecular cyclization with diazo compounds, to access three distinct classes of triazolo-[5,5]-fused heterocycles: triazolotriazoles, imidazotriazoles, and pyrazolotriazoles. Subsequent derivatization of these scaffolds furnishes high-nitrogen energetic compounds with excellent detonation properties, surpassing RDX in some cases and demonstrating strong potential as advanced gas-generating materials. This work establishes a versatile platform for the streamlined synthesis of structurally complex triazolo-[5,5]-fused heterocycles with broad implications for molecular design in energetic and functional materials.