Constructing Heat-Resistant and Insensitive Energetic Compounds with the Introduction of Cyano Group into Fused Pyrazolotriazine Skeleton

Fused pyrazolotriazine frameworks have been used to develop novel heat-resistant energetic compounds. Diazotization of 3,4-diamino-4-nitropyrazole (1) and 3-anmio-4,5-dinitropyrazole (ADNP) followed by treatment with malononitrile afford compounds 2 and 3, including fused pyrazolotriazine ring surrounded by amino and cyano groups, respectively. Compounds 2 and 3 were thoroughly characterized by multinuclear NMR spectroscopy, infrared spectroscopy, and elemental analysis. The molecular structures of 2 and 3 were further confirmed by single crystal X-ray diffraction with the densities of 1.794 and 1.817 g·cm^–3 (298 K), respectively. Moreover, compounds 2 and 3 have low impact and friction sensitivities (IS > 50 J, FS > 324 N). In particularly, compound 2 possesses the crossing stacking mode and high onset decomposition temperature of 370 °C, whose comprehensive performances are better than those of (2,2′,4,4′,6,6′-hexanitrostilbene) HNS and (2,6-bis(picrylamino)-3,5-dinitropyridine) PYX. The efficient method of malononitrile cyclization provides a new idea for the development of novel heat-resistant energetic compounds.