Transformations of C-adducts of 1,4-diazinium salts with dicarbonyl compounds into polycyclic systems

C-Adducts of 5-(het)aryl-2,3-dicyano-1-pyrazinium salts containing a residue of a 1,3-dicarbonyl compound at position 6 can be involved in the cyclization with hydrazine hydrate giving rise to pyrazino2,3-c]pyridazines along with the expected pyrazole derivatives. The reactions of the same σ^H-adducts with hydroxylamine unexpectedly afforded triazacyclopentaa]indene derivatives. The crystallographic data on the three-dimensional structures of new polycyclic compounds were obtained. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 639–643, March, 2008.