SYNTHESIS AND CHEMISTRY OF 1,3,5,7-TETRANITROCUBANE INCLUDING MEASUREMENT OF ITS ACIDITY, FORMATION OF O-NITRO ANIONS, AND THE FIRST PREPARATIONS OF PENTANITROCUBANE AND HEXANITROCUBANE

Nitro groups on alternate corners of cubane enhance the acidity of cub yl hydrogen (pK(a) similar to 21) and provide sufficient activation fo r ready anion formation. The sodium salt of 1,3,5,7-tetranitrocubane r eacts easily with electrophiles and leads thereby to yet more highly s ubstituted cubanes, like carbomethoxy- and (trimethylsilyl)tetranitroc ubane. Anions from these species are also easily formed and are useful for further substitution on the cubane nucleus. Dinitrogen tetraoxide reacts with the anion of tetranitrocubane to give 1,2,3,5,7-pentanitr ocubane, the first cubane to contain vicinal nitro groups. The reactio n probably involves oxidation of the anion to the corresponding radica l. Similarly, the anion of pentanitrocubane is used to prepare 1,2,3,4 ,5,7-hexanitrocubane, the most highly nitrated cubane made to date. Si ngle-crystal X-ray structural information is given for both penta- and hexanitrocubane.