N-functionalization of 3,4-dinitro-1H-pyrazol-5-amine (ADNP): Incorporating nitromethyl and diazidomethyl into energetic pyrazole derivatives

In the field of energetic materials, N -functionalization on pyrazoles faces challenges such as low nucleophilicity and harsh reaction conditions. In this study, the N -functionalization on 5-amino-3,4-dinitropyrazole (ADNP) gave two compounds 3,4-dinitro-1-(nitromethyl)-1 H -pyrazol-5-amine ( 5 ) and 1-(diazidomethyl)-3,4-dinitro-1 H -pyrazol-5-amine ( 6 ). The compounds 5 and 6 were characterized by IR, 1 H NMR, and 13 C NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Compound 5 , which was the isomer of 3,5-dinitro-1-(nitromethyl)-1 H -pyrazol-4-amine ( 1 ), was obtained from ADNP by electrophilic reaction. 5 has a packing coefficient (PC) of 73.6 % and a density of 1.828 g cm -3 , which surpasses its regioisomeric analogue 1 ( d = 1.76 g cm -3 ; PC = 72.4 %). An unanticipated nucleophilic substitution of 3,4,5-trinitro-1-(nitromethyl)-1H-pyrazole ( 2 ) with sodium azide led to diazidomethyl-functionalized 6 by a streamlined one-step process, and 6 exhibited high sensitivity to external stimuli (Impact Sensitivity: IS = 2 J, Friction Sensitivity: FS = 10 N) due to the presence of azido groups, making it a potential candidate for primary explosives. These compounds are considered as promising candidates for high energy density materials (HEDMs) due to their high density, outstanding heat of formation and good detonation properties. This study successfully achieved N -functionalization of 3,4-dinitro-1 H -pyrazol-5-amine (ADNP) by introducing nitromethyl and diazidomethyl groups, resulting in two novel energetic compounds. They exhibit high density, superior detonation performance, and tunable sensitivity properties, making them promising candidates for high-energy-density materials (HEDMs) and environmentally friendly primary explosives. • This study explores the selective synthesis at specific reaction sites of polynitropyrazoles. • Compound 6 was synthesized by an intriguing pathway to access gem-polyazidomethyl building blocks. • Compound 5 has a higher density and better detonation performance compared to the isomer.