Computational insight into the reactivity of FOX-7 and its bridge-ring energetic derivatives from Diels-Alder reactions

The reaction characteristics of FOX-7 and NH₂/NO₂-substituted oxazole compounds in the Diels-Alder reaction were studied, based on which six series of novel bridge-ring energetic compounds were designed. The reaction feasibility, energetic properties and stability of the designed compounds were extensively evaluated based on density functional theory. The preferred dienes tend to undergo normal or inverse Diels-Alder reactions with FOX-7. And, the formation of the most designed bridge-ring energetic compounds tends to follow a two-step reaction mechanism rather than the common one-step concerted cycloaddition mechanism. All the designed bridge-ring energetic compounds exhibited excellent detonation performance, except for P1 and P2 series compounds. In a comprehensive evaluation of detonation performance and stability, compounds P6-1 and P6-3 (ρ > 2.08 g cm⁻³, D > 9800 m s⁻¹, P > 44 GPa, h₅₀ values are comparable to that of CL-20) and compounds P4-1, P4-4, P5-1, and P5-4 (ρ: 1.952-1.976 g cm⁻³, D: 9474-9508 m s⁻¹, P: 40.5-41.5 GPa, h₅₀ values are superior to that of CL-20) are the most promising high-energy-density compounds. This study can provide some guidance for the extension of the derivative reaction of FOX-7, as well as the design and experimental synthesis of these novel bridge-ring energetic compounds.