STRUCTURE-ACTIVITY-RELATIONSHIPS IN (HALOALKYL)PYRIDAZINES - A NEW CLASS OF SYSTEMIC FUNGICIDES

3,6-Dichloro-4-(2-chloro-l,l-dimethylethyl)pyridazine (1) is one of the most active members of a series of new fungicides active against Oomycetes. We report on 66 compounds representing modifications of structure 1 and showing that only very limited variation in this structure is possible without loss of activity. Activity is retained only when bromine or iodine is substituted for the chlorine on the tert-butyl function. A second chlorine may be added to an adjacent methyl group without large loss of activity. A bromine may be substituted for the 3-chlorine, and to a lesser extent, methyls may be substituted for the ring chlorines. All other changes we explored resulted in partial or complete loss of activity. The parent compound is mobile within plant tissue, moving through the root system to control the pathogen and also toward the tip of the leaf when applied to the middle of the leaf. © 1990, American Chemical Society. All rights reserved.