Novel Ring Systems: Spiro[Cycloalkane] Derivatives of Triazolo- and Tetrazolo-Pyridazines

In orderto synthesize new pyridazine derivatives anellated with different nitrogen heterocyclic moieties, spirocycloalkane]pyridazinones were transformed into the corresponding thioxo derivatives via a reaction with phosphorus pentasulfide. The reaction of the formed 2,3-diazaspiro5.5]undec-3-ene-1-thiones with hydrazine provided the corresponding 1-hydrazono-2,3-diazaspiro5.5]undec-3-ene, whose diazotization led to the desired spirocyclohexane-1,8′-tetrazolo1,5-b]pyridazines. The reaction of dihydropyridazinethiones with benzhydrazide afforded the corresponding 7H-spiro1,2,4]triazolo4,3-b]pyridazin-8,1′-cyclohexanes]. As a result of our work, seven new pyridazinethione intermediates were prepared, which served as starting materials for the synthesis of two kinds of new ring systems: tetrazolo-pyridazines and triazolo-pyridazines. The six new annulated derivatives were characterized by physicochemical parameters. The new N-heterocycles are valuable members of the large family of pyridazines.