Abstract
A series of new 3-(substituted phenyl)-5-alkylidene-1, 3-oxazolidine-2, 4-dione derivatives was synthesized by reacting substituted phenyl isocyanates with 2-hydroxy-3-alkenoates prepared through an acid-catalyzed isomerization of 3, 3-disubstituted glycidates, and their herbicidal activities against various weeds as well as the crop safeties were examined. The herbicidal activities of these oxazolidinedione derivatives were primarily influenced by the substituents on the phenyl group and by the structure of the alkylidene moiety. The compounds having a 2, 4-dihalo-5-alkoxyphenyl moiety exhibited relatively higher herbicidal activities while the introduction of a long chain alkylidene group at the 5-position of the oxazolidine ring reduced the activity. The crop safety was found to be markedly affected by the substituent at the 5-position of the phenyl group and a cyclopentyloxy group seemed to be the most preferable one. Among the compounds synthesized, 3-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)-5-isopropylidene-1, 3-oxazolidine-2, 4-dione (KPP-314) was selected as a promising paddy rice herbicide. In green-house pot tests, KPP-314 exhibited an excellent activity against annual lowland weeds by pre- and post-emergence soil treatments at 150 to 450g a.i./ha with a wide safety margin between rice plant and Echinochloa oryzicola.
