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, ¹H NMR, and ¹³C 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.