Potential Insensitive and High-Energy Materials Based on a Pyrazole-Triazine-Oxadiazole Skeleton

The pyrazole-triazine-oxadiazole skeleton was constructed via introducing an oxadiazole ring onto a pyrazole-triazine fused ring through the cyclization reaction of a hydroximoylamine group. A series of heat-resistant compounds, namely, 3-(5-amino-1,2,4-oxadiazol-3-yl)-4,7-diamino-8-nitropyrazolo-5,1-c1,2,4triazine (4) and 7-amino-3-(5-amino-1,2,4-oxadiazol-3-yl)-8-nitro-1H-pyrazolo5,1-c1,2,4triazin-4-one (10), based on the pyrazole-triazine-oxadiazole skeleton were synthesized, exhibiting low sensitivity and high stability. Unexpectedly, oxidation of compound 4 afforded the ring-opened product 6, and the high-energy compound 3-(5-amino-1,2,4-oxadiazol-3-yl)-7-(nitroamino)-8-nitro-1H,4H-pyrazolo5,1-c1,2,4triazin-4-one (8) was synthesized via two distinct synthetic routes, with compounds 4 and 10 serving as the respective starting materials. Compared with the classic heat-resistant explosive HNS (Td = 318 °C, Dv = 7612 m·s-1, Dp = 24.3 GPa), compounds 4 and 10 have higher thermal stability (Td = 343 °C and Td = 325 °C, respectively) and superior detonation performance (Dv = 8317 m·s-1 and Dv = 7937 m·s-1, respectively), thereby demonstrating great potential as alternatives to HNS. Compound 8 (Dv = 8736 m·s-1) performs comparably to RDX (Dv = 8795 m·s-1, IS = 7.4 J, FS = 120 N) in detonation velocity but outperforms it in both sensitivity (IS = 15 J, FS = 192 N) and thermal stability (Td = 214 °C), indicating its potential as a high-energy explosive.