Synthesis of Advanced Pyrazole and N–N-Bridged Bistriazole-Based Secondary High-Energy Materials

In this work, we have synthesized 3,5-dihydrazinyl-4-nitro-1H-pyrazole (2), 9-nitro-1H-pyrazolo[3,2-c:5,1-c′]bis([1,2,4]triazole)-3,6-diamine (3), and N–N-bonded N,N′-{[4,4′-bi(1,2,4-triazole)]-3,3′-diyl}dinitramide (5) and its stable nitrogen-rich energetic salts in one and two steps in quantitative yields from commercially available inexpensive starting material 4,6-dichloro-5-nitropyrimidine (1). Along with characterization via nuclear magnetic resonance, infrared, differential scanning calorimetry, and elemental analysis, the structures of 2and 4–8were confirmed by single-crystal X-ray diffraction. Interestingly, 5–8show excellent thermal stability (242, 221, 250, and 242 °C, respectively) compared to that of RDX (210 °C). Detonation velocities of 2, 4, 6, and 7range from 8992 to 9069 m s–1, which are better than that of RDX (8878 m s–1) and close to that of HMX (9221 m s–1). All of these compounds are insensitive to impact (10–35 J) and friction (360 N) sensitivity. These excellent energetic performances, stabilities, and synthetic feasibilities make compounds 2, 4, 6, and 7promising candidates as secondary explosives and potential replacements for the presently used benchmark explosives RDX and HMX.