Pyrazolo[1,5-a]pyrimidine with similar “amino–nitro–amino” arrangement characteristics to TATB: a novel heat-resistant explosive with fused structure

Exploring heat-resistant explosives that are easy to synthesize is a major challenge in the research of energetic materials. In this study, two novel fused-ring energetic compounds, namely 3,6-dinitropyrazolo[1,5-a]pyrimidine-5,7-diamine (4) and 5-amino-3,6-dinitropyrazolo[1,5-a]pyrimidin-7(4H)-one (5), were successfully prepared via a simple synthetic method. In addition, their structure, thermal stability, mechanical sensitivity and detonation performance were fully explored. Noteworthily, compounds 4 and 5 both exhibit excellent thermal stability (TD(4) = 325 °C and TD(5) = 291 °C), particularly compound 4, which features an “amino–nitro–amino” arrangement similar to that of TATB and exhibits a high density of 1.88 g cm−3 and a greater thermal decomposition temperature than hexanitrostilbene (HNS, 316 °C). In addition, due to the aza-fused structure, 4 and 5 possess higher positive heats of formation (332.9 kJ mol−1 and 181.4 kJ mol−1) than LLM-105 (11.0 kJ mol−1). These advanced features endow 4 and 5 with superior detonation performance (Vd(4) = 8338 m s−1 and P(4) = 30.7 GPa; Vd(5) = 8097 m s−1 and P(5) = 29.8 GPa) than TATB (Vd = 8179 m s−1 and P = 30.5 GPa) and HNS (Vd = 7170 m s−1 and P = 21.8 GPa). This study enriches prospects for the molecular design and crystal engineering of novel energetic materials with admirable molecular stability.