Ko Wakabayashi

Quantitative structure-activity study of herbicidal N-aryl-3,4,5,6-tetrahydrophthalimides and related cyclic imides

Abstract The quantitative relationship between structure and inhibitory activity against the root growth of sawa millet of 30 N-aryl-3,4,5,6-tetrahydrophthalimides and 88 related N-aryl cyclic imide compounds (3-aryl-1,5-tetramethylenehydantoins, 4-aryl-1,2-tetramethylenetriazolidine-3,5-diones, and their thiocarbonyl analogs) was analyzed by means of physicochemical parameters of the aryl substituents and regression analysis. The results showed that, in each series of these classes of compounds, the position-specific steric effects of aromatic substituents, as represented by Verloops STERIMOL values, are highly important in determining the inhibitory potency of the compound.

STRUCTURE-ACTIVITY RELATIONSHIP OF CYCLIC IMIDE HERBICIDES

Abstract N-Aryl-3,4,5,6-tetrahydrophthalimides (I) and other two series of cyclic imide types of compounds (II & III) have been found active as pre-emergence or early post-emergence herbicides. The compounds showed activity at low rates on many grassy and broadleaf weeds and were exceptionally phytotoxic to hairy galinsoga, common purslane and toothcup. Futher biological and biochemical studies showed that these cyclic imide herbicides belonged to the category of diphenylether herbicides having 0-substituent(s) such as CNP or nitrofen in their mechanism of action. In the context of development of cyclic imide herbicides, an information has been obtained on the structural characteristics required for herbicidal activity and a hypothesis that the alkylene ring, the electrondonating moiety, the imide ring and p-substituted ary ring are the prerequisite for activity is presented.