Discovery, SAR, and putative mode of action of N-benzyl-2-methoxybenzamides as potential bleaching herbicides.

Background: Herbicides acting on biosynthesis of plant pigments have contributed greatly to weed control in recent years. In our previous studies, 2-methoxybenzamides were discovered as a novel type of lead compound for the development of bleaching herbicides.

Results: A total of 67 benzamide analogues were synthesized and evaluated for herbicidal activity. The structure-activity relationship (SAR) revealed that a methoxyl substitution at the 2-position of the benzoyl moiety is essential for the herbicidal activity of benzamide derivatives, and introduction of small substituents at the meta- or para-position of the benzylamine moiety is also beneficial. Compounds 4, 43 and 44 showed 100% inhibition against Abutilon theophrasti and Amaranthus retroflexus at an application rate of 150 g a.i. ha .

Conclusion: The relationship between the structure and herbicidal activity of 2-methoxybenzamides was discussed intensively. Compounds 4, 43 and 44 may serve as novel candidates with a bleaching effect. © 2021 Society of Chemical Industry.