Hydrolysis and Phytotoxic Activity ofN-Aryl-3,4,5,6-tetrahydroisophthalimides

The phytotoxic action of five N-aryl-3,4,5,6-tetrahydroisophthalimides (isoimides) synthesized was studied using green microalga (Scenedesmus acutus) and sawa millet (Echinochloa utilis). Isoimides had the same phytotoxic activity as that of imides and amide-acids. This fact indicates that isoimides are peroxidizing herbicides too. Their phytotoxic activity against E. utilis and S. acutus was studied in relation to conversion of isoimide to imide and/or amide-acid during the bioassay. The isoimides rapidly changed to the amide-acids and imides in cluture solution. The conversion rate depended on structures of their N-aryl residues. The phytotoxicity of isoimides may be mostly due to the corresponding amide-acids and/or imides. However, because the isoimides, N-{4-(4-chlorobenzyloxy)phenyl}-3,4,5,6-tetrahydroisophthalimide, which had a bulky p-substituent on N-aryl ring, slowly converted to the corresponding amide-acid and/or imide, this compound may have the intrinsic phytotoxicity of the isoimide itself.