Computational design of a notable nitrogen-rich energetic compound on the basis of Diels-Alder reactions

On the basis of Diels-Alder (D-A) reactions, a newly nitrogen-rich energetic compound, EC-1 (5,5,6,6-tetranitro-2,3-diazabicyclo[2.2.1]hept-2-ene), was constructed by selecting 4H-pyrazole (2N-III) and tetranitroethylene (TNE) as the starting materials. The most suitable diene 2N-III was screened by comparing the reactivity of 17 five-membered dienes. The density functional theory (DFT) method and the distortion/interaction (D/I) model revealed that the origin of the reactivity difference of the D-A reactions is from the distortion of the dienes, with the reactivity order of 3-azadienes < 1-azadienes < 2-azadienes. EC-1 (ΔG^‡ = 99.99 kJ mol⁻¹) has better synthesis feasibility and sensitivity than our previously studied trans-BIT (ΔG^‡ = 116.07 kJ mol⁻¹). The predicted crystal structure of EC-1 belongs most probably to the P2₁2₁2₁ space group.