Nucleophilic substitution reactions, molecular aggregation, structure and lipophilicity of 6-chloro-3-chloromethyl-1,2,4-triazolo[4,3-b]pyridazine

The synthesis of 6-chloro-3-chloromethyl-1,2,4-triazolo[4,3-b]pyridazine and its vicarious nucleophilic substitution products are described and characterized by spectroscopic methods and X-ray diffraction. The lipophilicities of the title compound, its acetate, and the derived 3-methyl tetrazolopyridazine have been measured and correlated with the chlorine substitution. The title compound co-crystallizes with acetic acid in the structure of the same symmetry and very similar layered arrangement as the crystals of its acetoxymethyl analog, despite the considerably different substituents and intermolecular contacts. The details of the intermolecular interactions are discussed.