Novel energetic furazans containing isomeric N-(azoxy)-dinitropyrazole moieties: Synthesis, characterization and comparison of properties

Novel energetic furazans 3a–3c and 4a–4c containing isomeric (3,4-dinitro-1H-pyrazol-1-yl)-NNO-azoxy and (3,5-dinitro-1H-pyrazol-1-yl)-NNO-azoxy moieties have been obtained. A synthetic approach to aminofurazans 3a and 4a involves the reaction of 1-amino-3,4-dinitro-1H-pyrazole or 1-amino-3,5-dinitro-1H-pyrazole with 2,2,2-trifluoro-N-(4-nitrosofurazan-3-yl)acetamide and dibromoisocyanuric acid, followed by removal of the trifluoroacetyl group. Transformations of the amino group in aminofurazans 3a and 4a gave the corresponding nitro (3b, 4b) and azo (3c, 4c) substituted furazans. The compounds synthesized exhibit high experimental enthalpies of formation (2093–2847 kJ·kg⁻¹), good thermal stabilities (onset decomposition temperatures 203–228 °C), acceptable densities (1.78–1.87 g·cm⁻³) and high detonation parameters (detonation velocities D = 8.71–8.99 km s⁻¹, detonation pressures p = 33.9–38.7 GPa). Nitro substituted furazans 3b, 4b and azo substituted furazans 3c, 4c have been evaluated as effective energetic fillers for solid composite propellants, providing specific impulse values 9–11 s higher than similar formulations based on RDX and HMX, and 4–6 s higher than similar formulations based on CL-20.