Abstract
A series of new 3-(5-alkoxy-2, 4-dihalophenyl)-5-alkylidene-1, 3-imidazolidine-2, 4-dione derivatives was synthesized and their herbicidal activities against various weeds were examined. The herbicidal activities varied with the substituents on the benzene ring and the compounds having a 5-alkynyloxy-4-chloro-2-fluorophenyl group exhibited relatively higher herbicidal activities. In the case of monocyclic Imidazolidinedione derivatives, introduction of an isopropylidene group at the 5-position and a lower alkyl group at the 1-position of the imidazolidinedione ring was most effective in enhancing the activity. In the case of bicyclic imidazolidinedione derivatives, 5, 6-dihydroimidazo [1, 5-a] pyridine derivatives gave a higher selectivity than tetrahydroimidazo [1, 5-a] pyridine derivatives, therefore, it was thought that the presence of a double bond was important for the crop safety. Among the compounds synthesized, a bicyclic imidazolidinedione compound, 2-(4-chloro-2-fluoro-5-propargyloxyphenyl)-5, 6-dihydroimidazo[1, 5-a]pyridine-1, 3[2H, 7H]-dione is considered to be the most promising candidate as a corn herbicide.
