Construction of fused N-oxide via in situ ring closure strategy: New pathway to high energy low sensitivity energetic compounds

A mild and efficient way to form fused N→O moiety by in situ ring closure reaction was proposed and studied. Compared with other methods to synthesize fused N-oxides, the new strategy is much safer and easier. The obtained compound, 4-amino-7-nitro-[1,2,4]triazolo[5,1-d][1,2,3,5]tetrazine-2-N-oxide (NTTO), was isolated with good purity and fully characterized. NTTO has a high density of 1.841 g⋅cm⁻³ and a high decomposition temperature of 262 °C. Compared with the traditional high energy insensitive energetic compound FOX-7, NTTO shows a higher detonation velocity of 8907 m⋅s⁻¹ and lower sensitivity (IS = 40 J, FS = 252 N), demonstrating a promising candidate as a high energy insensitive energetic material. Compared with the traditional ortho-C-amino/C-nitro structure, the formed 4-amino-1,2,3,5-tetrazine-2-oxide ring shows greater promise in designing energetic materials with high energy and low sensitivity.