Structure-Activity Relationships of Herbicidal Aryltriazolinones

✍ Scribed by Theodoridis, George

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 246 KB
• Volume: 50
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199708)50:4<283::aid-ps600>3.0.co;2-l

✦ Synopsis

A series of substituted aryltriazolinones, known to inhibit protoporphyrinogen oxidase, were prepared and their structureÈactivity requirements at positions 4 and 5 of the aromatic ring investigated. A QSAR equation obtained for substituents at the 5 position identiÐed the hydrophobicity term n and the Sterimol minimum width as the two parameters a †ecting in-vitro B 1 biological activity. Greenhouse pre-emergence activity correlated with in-vitro activity and the hydrophobicity term n of the substituent at that position. It was found that the phenoxy-4-oxyacetate group at aromatic position 5 was an outlier and had to be considered separately. SAR analysis of substituents at aromatic position 4 revealed that two di †erent models were required to explain all observed substituent e †ects. In the Ðrst model, where the 5 position was occupied by hydrogen, the 4-chlorobenzyloxy group at aromatic position 4 gave the best compound. The second model, where the 5 position of the aromatic ring was occupied by a group other than hydrogen, resulted in a QSAR equation, previously derived, which links substituent e †ects at position 4 with n and with the electronic para inductive term

In this model the chloro group provides F p . optimum biological activity. The need to separate the aryltriazolinone herbicides into several di †erent classes in order to explain their substituent e †ects at aromatic positions 4 and 5 could be rationalized if more than one binding conformation, within the same binding site, is possible.