Synthesis of Pyrazole-Fused Heterocyclic N-Nitroacetamides with High Energy and Low Sensitivity.

In this study, pyrazole-fused heterocyclic N-nitroacetamide explosives 4-amino-7-nitramine-8-nitropyrazolo5,1-c1,2,4triazine-3-nitrocarbamoyl (2) and 4-amino-7,8-dinitropyrazolo5,1-c1,2,4triazine-3-nitrocarbamoyl (4) were synthesized through the nitration of cyano groups, featuring high energy and low sensitivity. Meanwhile, 7-amino-8-nitro-4-oxo-1,4-dihydropyrazolo5,1-c1,2,4triazine-3-carbonitrile (6) (Dv = 8233 m s-1 and Td = 366 °C) and potassium (7-amino-8-nitro-4-oxo-1,4-dihydropyrazolo5,1-c1,2,4triazin-3-yl)methanamide (7) (Dv = 7573 m s-1 and Td = 369 °C) were synthesized via hydroxylation of the amino group in 4,7-diamino-8-nitropyrazolo5,1-c1,2,4triazine-3-carbonitrile (1). Both compounds 6 and 7 exhibit acceptable detonation velocity and high thermal stability. In comparison to previous N-nitroacetamide explosives, compound 2 has superior density and detonation performance (ρ = 1.94 g cm-3, Dv = 9259 m s-1, and Dp = 39.4 GPa), higher thermal stability, and lower sensitivity (Td = 166 °C, IS = 18 J, and FS = 120 N). Meanwhile, 4 (8820 m s-1) performs comparably to RDX (Dv = 8795 m s-1) but has the highest thermal stability (Td = 167 °C) and lowest sensitivity (IS = 23 J and FS = 144 N) compared to previous N-nitroacetamide explosives. The superior detonation performance and lower sensitivity of N-nitroacetamide explosive 2 thereby demonstrate its great potential as an alternative to HMX.