A domino reaction from a sensitive azide: the impact of positional isomerism on chemical reactivity featuring ortho azido/nitro substituted derivatives

Abstract

This study highlights for the first time the impact of positional isomerism on chemical reactivity which involves a domino reaction, salt formation, cyclization, and nucleophilic substitution. The unprecedented reactivity occurs upon treating sensitive 5-azido-3,4-dinitropyrazole (1) with nitrogen rich bases. This results in the development of the first examples of fused catenated N₅ pyrazolo[1,5-d]tetrazole-based energetic salts. The compound structures of 1, 2, and 3 were obtained by single-crystal analysis. Compounds 2 (D_v: 9202 m s⁻¹; P: 32.08 GPa) and 3 (D_v: 8749 m s⁻¹; P: 31.26 GPa) displayed excellent detonation properties (calculated) and good sensitivities (IS ≥ 20 J; FS ≥ 240 N), which are comparable to RDX. The thermal stability of compound 2 (185 °C) further suggests its significant potential use as a secondary explosive. Compound 1 exhibits high detonation properties (D_v: 9023 m s⁻¹; P: 35.3 GPa) and sensitivity to external stimuli (IS: 8 J; FS: 80 N), indicating it has potential as a metal-free primary explosive.