Study of the Formation and Thermal Decomposition of an Azo-Bridged Tricyclic Ring System, Zoltán Novák, Zoltán Vincze, Zsuzsanna Czégény, Gábor Magyarfalvi, David M. Smith, András Kotschy, Eur. J. Org. Chem. 2006, 15, 3358-3363. DOI: 10.1002/ejoc.200600058 | [Full Text Link]

1-Amino-2-methyl-1,3-pentadienes were treated with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate to give diazatricyclo[2.2.2.0]octenes and dimethyl 4-methylpyridazine-3,6-dicarboxylate, the product distribution being largely dependent on the nature of the amino substituent. Under similar conditions the analogous 1-morpholino-1,3-butadiene afforded dimethyl pyridazine-3,6-dicarboxylate as the major product. The tricyclic products underwent selective thermal decomposition to give dimethyl 4-methylpyridazine-3,6-dicarboxylate in excellent yield. The proposed mechanism of the formation as well as of the decomposition was supported by quantum chemical calculations and experimental evidence.