4-Chlorophthalazin-1-amine is used to prepare 2-phenylimidazo[1,2-b]pyridazine derivatives as anthelmintics against Haemonchus contortus. It is also used to synthesize imidazo[2,1-a]phthalazines, potential inhibitors of p38 MAP kinase, prediction of binding affinities of protein ligands.