1990 Volume 35 Issue 3 Pages 273-281
New 2, 6-dimethyl-4-pyridone-3-carboxamide derivatives were synthesized and their herbicidal activity against Echinochloa oryzicola and safety for transplanted rice were examined.
1) For the pre-emergence herbicidal activity against Echinochloa oryzicola and the safety for transplanted rice, it was found essential that the 3 (R3)-and 1 (R1)-position of the 4-pyridone ring be substituted by anilide and benzyl groups, respectively (Tables 3, 4). The introduction of a methyl, chloro or fluoro group to the para-position of the benzyl moiety (Y) further enhanced the activity (Table 5).
2) The 1-benzyl derivatives were tested in vials for their herbicidal activity against Echinochloa oryzicola and the effects of substituents of the benzyl moiety (Y) were examined quantitatively with substituent parameters by regression analysis. The variations in the activity were rationalized in terms of steric parameters, the optimal value being Eso, Esm=0 and Esp=-0.90 (Table 7, Eq. (1)).
3) From the results so far obtained, 1, 4-dihydro-2, 6-dimethyl-1-(4-methylphenylmethyl)-4-oxo-N-phenyl-3-pyridinecarboxamide (code number, DLH-0213) was selected due to it's high herbicidal activity and selectivity. DLH-0213 effectively controlled Echinochloa oryzicola from the pre-emergence to the 1.5 leaf stages and actively controlled some sedge weeds (Cyperus difformis, Scirpus juncoides, Cyperus serotinus) at pre-emergence at a dose of 10g a. i./a (Tables 9, 10).
