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Synthesis 1992; 1992(9): 879-883
DOI: 10.1055/s-1992-26251
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Synthese von Imidazo- und Diimidazo[1,2,4,5]tetrazinen; zur Tautomerie von Dihydro-1,2,4,5-tetrazinen

Heinrich Wamhoff* , Harald W. Strobl, Martin Jansen, Martina Ralle
  • *Institut für Organische Chemie und Biochemie der Universität Bonn; Gerhard-Domagk-Str. 1, D-5300 Bonn 1, Germany
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Publication Date:
17 September 2002 (online)

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Synthesis of Imidazo- and Diimidazo[1,2,4,5]tetrazines; For Tautomerism of Dihydro-1,2,4,5-tetrazines Dimethyl 1,4-dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate (1) reacts with isocyanates to afford the 2,7-disubstituted 1H6H -diimidazo[1,5-b: 1′,5′-e] [1,2,4,5]tetrazine-1,3,6,8(2H,7H)-tetrones 2a-m, a hitherto unknown ring system. The linear annulation of 2m was established by X-ray analysis, and as a consequence the 1,4-dihydro tautomer found to be the main constituent of all other potential isomers. Compound 1 reacts with isothiocyanates to give the corresponding 1,6-dithioxo derivatives 5a,b as well as the 7-substituted methyl 2,6,7,8-tetrahydro-8-oxo-6-thioxoimidazo[1,5-b] [1,2,4,5]tetrazine-3-carboxylates 6b,c respectively, while the unsymmetrically substituted 2-tert-butyl-7-(4-chlorophenyl)-6-thioxo-1H, 6H-diimidazo[1,5-b: 1′,5′-e] [1,2,4,5]tetrazine-1,2,8-(2H,7H)-trione (8) is obtained from 6c and the corresponding isocyanate.