Synthesis of Pyrazole-Fused Heterocyclic <i>N</i> -Nitroacetamides with High Energy and Low Sensitivity

In this study, pyrazole-fused heterocyclic <i>N</i>-nitroacetamide explosives 4-amino-7-nitramine-8-nitropyrazolo[5,1-<i>c</i>][1,2,4]triazine-3-nitrocarbamoyl (<b>2</b>) and 4-amino-7,8-dinitropyrazolo[5,1-<i>c</i>][1,2,4]triazine-3-nitrocarbamoyl (<b>4</b>) were synthesized through the nitration of cyano groups, featuring high energy and low sensitivity. Meanwhile, 7-amino-8-nitro-4-oxo-1,4-dihydropyrazolo[5,1-<i>c</i>][1,2,4]triazine-3-carbonitrile (<b>6</b>) (<i>D</i>_v = 8233 m s^-1 and <i>T</i>_d = 366 °C) and potassium (7-amino-8-nitro-4-oxo-1,4-dihydropyrazolo[5,1-<i>c</i>][1,2,4]triazin-3-yl)methanamide (<b>7</b>) (<i>D</i>_v = 7573 m s^-1 and <i>T</i>_d = 369 °C) were synthesized via hydroxylation of the amino group in 4,7-diamino-8-nitropyrazolo[5,1-<i>c</i>][1,2,4]triazine-3-carbonitrile (<b>1</b>). Both compounds <b>6</b> and <b>7</b> exhibit acceptable detonation velocity and high thermal stability. In comparison to previous <i>N</i>-nitroacetamide explosives, compound <b>2</b> has superior density and detonation performance (ρ = 1.94 g cm^-3, <i>D</i>_v = 9259 m s^-1, and <i>D</i>_p = 39.4 GPa), higher thermal stability, and lower sensitivity (<i>T</i>_d = 166 °C, IS = 18 J, and FS = 120 N). Meanwhile, <b>4</b> (8820 m s^-1) performs comparably to RDX (<i>D</i>_v = 8795 m s^-1) but has the highest thermal stability (<i>T</i>_d = 167 °C) and lowest sensitivity (IS = 23 J and FS = 144 N) compared to previous <i>N</i>-nitroacetamide explosives. The superior detonation performance and lower sensitivity of <i>N</i>-nitroacetamide explosive <b>2</b> thereby demonstrate its great potential as an alternative to HMX.