Regioisomeric Switching via Thermal Rearrangement: Toward Safer High-Performance Energetic Materials

High-energy density materials (HEDMs) demand precise structural and energetic control to achieve optimal detonation performance, thermal stability, and insensitivity. Now we report a thermally induced rearrangement in the cine-substitution of 1,3,4-trinitropyrazole with 5-aminotetrazole, resulting in two regioisomeric pyrazole-tetrazole frameworks. At room temperature, nucleophilic substitution at the more reactive tetrazole N1-position gave the kinetic product, 1-(3,4-dinitro-1<i>H</i>-pyrazol-5-yl)-1<i>H</i>-tetrazol-5-amine (<b>1</b>), which undergoes thermal rearrangement to form a C5-NH-linked thermodynamic isomer, <i>N</i>-(3,4-dinitro-1<i>H</i>-pyrazol-5-yl)-2<i>H</i>-tetrazol-5-amine (<b>2</b>) upon heating via a Dimroth-like rearrangement. To enhance performance and safety, compound <b>2</b> was converted into energetic salts, with the hydroxylammonium (<b>2b</b>, Dv: 9412 m/s) and hydrazinium salts (<b>2c</b>, Dv: 9441 m/s) exhibiting superior detonation velocities, superior to HMX. Meanwhile, nitration of the kinetic product yielded <i>N</i>-(1-(3,4-dinitro-1<i>H</i>-pyrazol-5-yl)-1<i>H</i>-tetrazol-5-yl)nitramide (<b>3</b>), which demonstrated the highest detonation velocity (Dv: 9451 m/s), exceeding HMX, while its energetic salts further improve stability with optimized performance. Additionally, carbonyl azide functionalization of <b>1</b> resulted in (3,4-dinitro-1<i>H</i>-pyrazol-5-yl)carbamoyl azide (<b>4)</b>, which displayed the highest detonation properties (Dv: 8799 m/s; P: 33.2 GPa) among carbonyl azides, comparable to RDX. This study highlights thermally controlled regioisomeric switching as a promising strategy for designing safer, high-performance energetic materials.