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A series of new trifluoromethyl‐substituted phenyl alkyl ketoxime esters of Bispyribac were synthesized as potential herbicides. All synthesized compounds were characterized by nuclear magnetic resonance (NMR) spectroscopy and high‐resolution mass spectrometry (HRMS). Sprout method and foliar spray method were used to study the herbicidal activity of the synthesized compounds. Among all synthesized compounds, compound 3 (4‐trifluoromethylphenyl n‐butyl ketoxime ester of Bispyribac) exhibits the highest herbicidal activity against Echinochloa crusgalli (L.) Beauv with median effect dose (ED50) of 1.7 μg/mL in pre‐emergence herbicidal activity study. The structure‐activity relationship analysis indicates that trifluoromethyl substitution on the phenyl group exhibits better activity than methoxy and methyl substitution on the phenyl group. The alkyl chain length also affects the activity significantly and the optimal alkyl chain length is four among the tested compounds. However, the substitution position of trifluoromethyl exhibits very limited influence on the activity. In post‐emergence herbicidal activity study, compound 3 (ED90 69.1056 g/hm2) exhibits better herbicidal activity against Echinochloa crusgalli (L.) Beauv than Pyribenzoxim (ED90 99.0810 g/hm2). Moreover, compound 3 exhibits better safety to hybrid rice variety II you 084 and rice variety Nanjing 44 than Pyribenzoxim in crop safety study. Compound 3 may serve as a lead compound for future herbicide discovery. [ABSTRACT FROM AUTHOR]

A series of substituted acetophenone oxime esters of Pyrithiobac were synthesized as potential herbicides. The structures of the synthesized new compounds were confirmed by 1H NMR, 13C NMR, HRMS, and X‐ray single‐crystal diffraction (XRD). The pre‐emergence and post‐emergence herbicidal activity studies show that 4‐CF3 (6 f), 4‐NO2 (6 i), 4‐NH2 (6 j), 4‐F (6 l), and 2,4‐2OCH3 (6 s) substituted acetophenone oxime esters of Pyrithiobac exhibit better pre‐emergence and post‐emergence herbicidal activities against monocotyledon and dicotyledon weeds than other synthesized new compounds. In pre‐emergence herbicidal activity study, 6 f, 6 i, 6 j, 6 l, and 6 s exhibit similar herbicidal activities against monocotyledon and dicotyledon weeds as compared to Staple (Pyrithiobac‐sodium). In post‐emergence herbicidal activity study, 6 f, 6 i, 6 j, 6 l, and 6 s exhibit similar herbicidal activities against dicotyledon weeds and better herbicidal activities against monocotyledon weeds as compared to Staple. Compounds 6 i and 6 l with high herbicidal activities and similar binding mode with acetolactate synthase as compared to Staple were further subjected to crop safety study. The results show that the safety of compound 6 l to cotton is as good as Staple and better than 6 i. The present work indicates that compound 6 l may serve as a new candidate for potential herbicides. [ABSTRACT FROM AUTHOR]

O‐(2,6‐bis(4,6‐dimethoxypyrimidin‐2‐yloxy)benzoyl)oxime 3‐trifluoromethylacetophenone (HB‐002) was synthesized as potential acetolactate synthetase (ALS)‐inhibiting herbicides. HB‐002 was characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, high resolution mass spectrometer (HRMS), and X‐ray single‐crystal diffraction. The herbicidal activities of HB‐002 against four weeds were studied in greenhouse. The results show that the control effects of HB‐002 on Eclipta prostrata L. and Cyperus difformis are very weak. However, HB‐002 exhibits higher herbicidal activity against Leptochloa chinensis (L.) Nees than that of Pyribenzoxim. HB‐002 also shows certain control effect on Echinochloa oryzoides (Ard.) Flritsch. Molecular docking simulation was performed to study the binding affinity and probable binding modes of HB‐002 with ALS. In the binding mode, the trifluoromethyl group of HB‐002 forms two halogen bonds (fluorine) with ALS, contributing to the lower binding free energy of HB‐002 (‐45.336 kcal/mol) as compared to Pyribenzoxim (‐40.1286 kcal/mol) and m‐trifluoromethyl Pyribenzoxim (‐44.451 kcal/mol). The present work suggests that HB‐002 may serve as a new candidate for potential herbicides. [ABSTRACT FROM AUTHOR]