Nitrogen, heterocyclic compounds piperazine

Moore and Willer reported the synthesis of some nitramine explosives containing a furazan ring fused to a piperazine ring. The tetranitramine (46) is synthesized from the condensation of 3,4-diaminofurazan (DAF) (24) with glyoxal under acidic conditions followed by A-nitration of the resulting heterocycle (45). The calculated performance for the tetranitramine (46) is very high but the compound proves to be unstable at room temperature. Instability is a common feature of heterocyclic nitramines derived from the nitration of aminal nitrogens. 

Yet another approach to these compounds consists of substituting the piperazine ring onto the preformed heterocyclic moiety. Ullman condensation of the substituted thiosalyciclic acid (40-1) with ort/zo-chloronitrobenzene results in the displacement of chlorine by thiophenoxide and the formation of the thioether (40-2). The nitro group in this last intermediate is then reduced to an aniline (40-3) the resulting amino acid is then cyclized thermally to the lactam (40-4). Treatment of that with phosphorus oxychloride gives the imino chloride (40-5). Reaction with N-methylpiperazine leads to the replacement of chlorine by nitrogen and the formation of clothiapine (40-6) [39]. 

For the identification of piperazine derivatives powder X-ray diffraction of their picrates has been proposed (113) for gas chromatography of heterocyclic nitrogen compounds on columns with inorganic salts see (114). 

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