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.