Synthesis and crystal structure of 10-(4-nitrobenzyl)-3,7,9,11-tetraoxo-2,4,6,8,10-pentaaza[3.3.3]propellane

N^3a,N^6a-Dibenzyl-2,5-dioxotetrahydroimidazo[4,5-d]imidazole-3a,6a(1H,4H)-dicarboxamide was obtained by the reaction of diethyl 2,5-dioxotetrahydroimidazo[4,5-d]imidazole-3a,6a(1H,4H)-dicarboxylate with benzylamine, and cyclised to give 10-benzyl-3,7,9,11-tetraoxo-2,4,6,8,10-pentaaza[3.3.3]propellane with p-TsOH as catalyst. 10-(4-nitrobenzyl)-3,7,9,11-tetraoxo-2,4,6,8,10-pentaaza[3.3.3] propellane was afforded by the nitration of the benzyl derivative in 65-68% nitric acid. The structure of 10-(4-nitrobenzyl)-3,7,9,11-tetraoxo-2,4,6,8,10-pentaaza[3.3.3]propellane was further confirmed by single-crystal X-ray diffraction. The syntheses of these propellane derivatives have several advantages such as mild reaction conditions, operational simplicity, and excellent yields.