Synthesis and herbicidal activity against barnyard grass of novel diarylmethanone O-(2,6-bis((4,6-dimethoxypyrimidin-2-yl)oxy)benzoyl)oximes.

Pyribenzoxim is an excellent herbicide that can effectively control barnyard grass. However, there're few reports on its structural analogs and SAR, which makes pyribenzoxim an isolated case. In this paper, a series of diarylmethanone oxime esters characterized by pyridine heterocycles were designed and synthesized for herbicidal screening and SAR investigating against barnyard grass.At 1.17 ~ 37.5 μg/mL greenhouse treatment, the title compounds showed positive dose-toxicity correlation to barnyard grass plants, and the damage became more and more serious with the time. When the concentration was up to 18.75 μg/mL and above, obvious damages were observed in 3 days, most plants died in 7 days and completely died in 14 days. Damages also occurred in different degrees when the concentration was lower than 9.38 μg/mL. The selected compounds 5-20 and 5-21 showed excellent control effects on Echinochloa crusgalli (L.) Beauv., Leptochloa chinensis (L.) Nees, Cyperus difformis L. and Lindernia procumbens (Krock.) Philcox in paddy fields, which was slightly better than pyribenzoxim.SAR analysis of greenhouse data revealed that the type and position of substituents on aromatic rings had great influences on the activity, but the LogP values were not correlated obviously with it. Combined with both compound 5-20 and 5-21, which showed moderate and excellent activity in greenhouse experiment, exhibited excellent activity in controlling barnyard grass in field, we conclude that pyribenzoxim analogues probably act as prodrugs, and this might be the direction that needs to be paid attention on structural optimization of the herbicide in future. This article is protected by copyright. All rights reserved.