Nitration of Tricyclic Compound Bis([1,2,4]triazole)[1,5-b:3′,4′-f]pyridazin-8-amine: Mechanistic Insights and Synthetic Exploration

The nitration reaction plays a pivotal role in the construction and synthesis of energetic compounds. A new [5,6,5]-tricyclic compound bis([1,2,4]triazole)[1,5-b:3′,4′-f]pyridazin-8-amine (4) was synthesized, and its nitration reaction was investigated thoroughly. The nitrated products 5·H₂O, 6, 8, and 9 and rearrangement products 7 were obtained by nitration screening performed across a range of temperature gradients (0–100 °C), acid concentrations (HNO₃ = 40% to 100%), nitration systems (HNO₃ and HNO₃/H₂SO₄), and reaction durations (1 h–12 h). A new methodology for azasydnone synthesis is established by the synthesis of 7. The nitration and rearrangement reaction mechanism was fully studied by quantum chemical calculations. Compound 9 has good thermal stability (T_dec = 222 °C), high detonation properties (v = 8554 m·s^–1), and insensitivity (IS > 40 J; FS > 360 N). These findings provide deep mechanistic insights while broadening the synthetic landscape of fused-ring nitration.