Polynitro-functionalized 4-phenyl-1H-pyrazoles as heat-resistant explosives

A new class of heat-resistant explosives was synthesized by coupling N-methyl-3,5-dinitropyrazole with polynitrobenzene moieties through carbon-carbon bonds. Simple Pd(0)-based Suzuki cross-coupling reactions between N-methyl-4-bromo-3,5-dinitropyrazole and 4-chloro/3-hydroxy-phenylboronic acid followed by nitration, amination and oxidation lead to the formation of C-C connected penta-nitro energetic derivatives 6 and 10. Various other energetic derivatives, such as amino (5), azido (7), nitramino (8) and energetic salts (11-14), were also explored to fine-tune their properties. All the compounds were thoroughly characterized using IR, NMR [H-1, C-13{H-1}], differential scanning calorimetry (DSC), elemental analysis, and HRMS studies. Compounds 5, 10 and 13 were further characterized through N-15 NMR, and the crystal structures of 6 and 14 were confirmed through single-crystal X-ray diffraction studies. The physicochemical and energetic properties of all the energetic compounds were explored. Most of the synthesized compounds demonstrated high thermal stability (decomposition temperature T-dec > 250 ?), among which compounds 5 and 6 showed excellent thermal stability, having decomposition temperatures above 300 ?. The excellent thermal stability, acceptable sensitivity and good energetic properties of compounds 5, 6, 10 and 13 make them promising heat-resistant explosives. Furthermore, these compounds were found to be more thermally stable than the known N-methyl-3,5-dinitropyrazole-based and C-N coupled 3,4,5-trinitrobenzene-azole-based energetic compounds.

Automated summary

A new class of heat-resistant explosives was synthesized by coupling N-methyl-3,5-dinitropyrazole with polynitrobenzene moieties through carbon-carbon bonds. Various derivatives were explored to fine-tune their properties. The compounds showed high thermal stability and promising properties as heat-resistant explosives.