1.3.5.7- Tetrazocines

Semi bull valcncs are well-known intermediates in the synthesis of cyclooctatetraenes, 1,5-diazo-cines and 1,3,5,7-tetrazocines. There are also some examples for the synthesis of azocines, although so far only for W-substituted lactam derivatives, e.g. 1.25,26... 

Semibullvalenc systems with two incorporated nitrogen atoms readily isomerize to eight-mem-bered rings,44 as in the corresponding formation of azocines (see Section 1.1.1.1.2.) and 1,3,5,7-tetrazocines (see Section 1.7.1.4.). 

Acid-catalyzed cyclization of thiosemicarbazide 1 leads to the 1,2,4,6-tetrazocine 2.5... 

Most of the reported 1,2,5,6-tetrazocine systems probably do not exist in the monocyclic form but rather as the tetraazapentalene betaine structure (see Introduction) 2 3 7"13 for the tetra-phenyl-substituted system, the compound does actually exist as the mesoionic tetraphenyl-[1,2.3]triazolo[l,2-h][l,2,3]triazole, as determined by H and 13C NMR spectroscopy.15 The following syntheses arc therefore questionable. 

The method most often described for the synthesis of 1,2,5,6-tetrazocines consists of the self-condensation of 1,2-diketone monohydrazones 1 14.16-19... 

Dimethyl 4,8-diphenyl-l,2,5,6-tetrazocine-3,7-dicarboxylate (3, vide supra) can be saponified and dccarboxylated in excellent yield.18... 

The condensation of dihydrazones of aryl-substituted 1,2-diketones with aryl-substituted 1,2-diketones has also been described, albeit with rather low yields (up to 15 %).20 Subsequently, it was explicitly shown that this reaction leads to the same products as the dimerization of benzil monohydrazones, i.e. the 1,2,5,6-tetrazocine system, is not produced, rather the bicyclic tetraazapentalene system is obtained,21... 

The synthesis of 1,3,5,7-tetrazocines 3 can be accomplished by oxidation of tetraazapentalene derivatives 1 the likely formed tetraazasemibullvalene intermediates 2 cannot be trapped.22 25... 

The diethoxy derivative 4 can be transformed to the monolactame 5 by stirring an ethereal solution with silica gel, or used in substitution reactions to afford other derivatives, e g. JV,Ar,jV, jV -tetraethyl-4,8-dimethyl-l, 3,5,7-tetrazocine-2,6-diamine (6).23-24... 

Triazolo[l,2-a]triazolediylium salts 7 can be reductively transformed to the corresponding 1,3,5,7-tetrazocine system.26... 

Thyagarajan and Majumdar (Ref 18) have studied the condensations of urethanes with formaldehyde under various exptl conditions and accomplished the selective synthesis of either six-membered 1,3,5-triazines or eight-membered 1,3,5,7-tetrazocines. These are nonnitrated analogs of RDX and HMX respectively. Their results are summarized in Fig 4... 

TMAD= Me2NCON=NCONMe2 DHTD = 4,7-dimethyl-3,5,7-hexahydro-l,2,4,7-tetrazocin-3,8-dione Tsudoda. T. Nagaku, M. Nagino, C. Kawamura, Y. Ozaki, F. Hioki, H. Ito, S. Tetrahedron Lett, 1995, 36, 2531... 

Dinitrophenylacetyl chloride 2.4- Dinotrophenylhyd razine 1,3,5,7-Tetranitroperhydro-1,3,5,7-tetrazocine... 

Monteil-Rivera F, L Paquet, A Halasz, MT Montgomery, J Hawari (2005) Reduction of octahydro-l,3,5,7-tetra-nitro-l,3,5,7-tetrazocine by zero-valent iron product distribution. Environ Sci Technol 39 9725-9731. 

Reed Canary Grass Phalaris arundinacea) was grown in liquid culture and exposed to RDX that was metabolized to the potentially toxic 4-nitro-2,4-diazabutanal (Just and Schnoor 2004). This metabolite is also produced from RDX by strains of Rhodococcus sp. and from the homologous octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine (HMX) by Phanerochaete chrysosporium. 

HMG-CoA reductase inhibitors (Statins), 5 137, 138-140t, 142-143 HMX (High Melting eXplosive octahydro-1,3,5,7- tetranitro-l,3,5,7-tetrazocine), 70 735-736... 

Energetic Materials. 2. Deuterium Isotope Effects and Isotopic Scrambling in Condensed-Phase Decomposition of Octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine. 

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