Natsuko Okano

Synthesis and Herbicidal Activity of New Imidazolidinedione Derivatives

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 activites. 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.