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-1 H -pyrazole ( 2 ), 9-nitro-1 H -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 2 and 4–8 were confirmed by single-crystal X-ray diffraction. Interestingly, 5–8 show excellent thermal stability (242, 221, 250, and 242 °C, respectively) compared to that of RDX (210 °C). Detonation velocities of 2, 4, 6, and 7 range 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 7 promising candidates as secondary explosives and potential replacements for the presently used benchmark explosives RDX and HMX.