Pyridopyridazines. III. The synthesis and reactions of 5- and 8-Chloropyrido[2,3d]pyridazine

Abstract

Pyrido[2,3-d]pyridazin-5-one and -8-one have been synthesized by several methods and converted into 5- and 8-chloropyrido[2,3- d]pyridazine. These latter compounds were also prepared by dehydrazination of the requisite chlorohydrazino- pyrido[2,3-d]pyridazines. Some nucleophilic reactions of the chloropyrido[2,3-d]- pyridazines have been studied. Cyclization of 5- and 8-hydrazino- and 5,8-dihydrazino-pyrido[2,3-d]pyridazine with formic acid has led to the new heterocyclic compounds pyrido[2,3-d]- and pyrido[3,2-d]-s- triazolo[4,3-d]pyridazine.