Synthesis and Herbicidal Activities of Novel Substituted Acetophenone Oxime Esters of Pyrithiobac

Abstract A series of substituted acetophenone oxime esters of Pyrithiobac were synthesized as potential herbicides. The structures of the synthesized new compounds were confirmed by 1 H NMR, 13 C NMR, HRMS, and X‐ray single‐crystal diffraction (XRD). The pre‐emergence and post‐emergence herbicidal activity studies show that 4‐CF 3 ( 6 f ), 4‐NO 2 ( 6 i ), 4‐NH 2 ( 6 j ), 4‐F ( 6 l ), and 2,4‐2OCH 3 ( 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.