Abstract
New photodynamic herbicidal 2,3-dihydro-2,2,4,5,6-pentamethylbenzofuran-5-yl, (I) and 2,3-dihydro-2-ethyl-2,4,5,6-tetramethylbenzofuran-5-yl, (II) substituents in 6-benzofury-2-[1-( alkoxyimino )alkyl]-3 hydroxycyclohex-2-en-1-one derivatives were synthesized and their herbicidal activities against rice plant (Oryza sativa L.), barnyard grass (Echinochloa crus-galli) and pickerel weed (Monochoria vaginalis presl.) were measured under submerged pre and post-emergence conditions. Particularly, a series of (I) compounds showed good selective herbicidal activities between the 3 leaf stage of rice plant and barnyard grass at rates of $0.25{\sim}0.0007kg/ha$. The structure activity relationships (SAR) on the herbicidal activity with changing N-alkoxy groups were discussed quantitatively. According to the SAR results, it was expected that the selectivity factor between seed of rice plant and barnyard grass should be rely on the N-alkoxy groups with bigger dipole moment and bigger (or smaller) $B_3$ constant than optimal value $(B_3)_{opt.}=4.41{\AA}$. Compared with (I), the (II) substituents showed more superior herbicidal activities.
광역동 제초성 6-benzofuryl-2-[1-(alkoxyimino)alkyl]-3-hydroxycyclohex-2-en-1-one 유도체 중 2,3-dilly-dro-2,2,4,5,7-pentamethylbenzofuryl(I) 및 2,3-dihydro-2-ethyl-2,4,5,7-tetramethylbenzofuryl(II) 치환체들을 합성하여 발아 전 후, 벼(Oryza sativa L., 직파 및 3엽기 이앙)와 강피(Echinochloa crus-galli) 그리고 물달개비(Monochoria vaginalis presl.)에 대한 제초활성을 측정한 결과, (I)은 $0.25{\sim}0.0007kg/ha.$의 농도 수준에서 벼의 발아 후, 3엽기와 강피 간에 선택적인 제초활성이 관찰되었다. 또한, N-alkoxy-기가 변화함에 따라 제초활성에 미치는 영향을 정량적으로 검토한 바, 직후 벼와 강피 사이에 선택성 조건은 폭에 관한 $B_3$ 상수의 적정 값$(B_3)_{opt.}=4.41$을 벗어난 쌍극자능율이 큰 치환체이어야 할 것으로 예상되었으며 (II)가 (I)보다 다소 우세한 제초활성을 나타내었다.
