4-chloro-5-methoxy-2-(beta,-trifluoro)ethyl-3(2H)-pyridazinone

4-chloro-2-(2-hydroxyethyl)-5-methoxypyridazin-3-one

4-chloro-5-ethoxy-2-ethylpyridazin-3-one

3,4-dichloro-5-methoxypyridazine