Synthesis and herbicidal activities of 2‐((3‐pyridinyl‐2‐oxo‐2,3‐dihydrobenzo[d]thiazol‐6‐yl)oxy)propionates

Abstract

AbstractBACKGROUNDThe discovery of lead compounds is fundamental to herbicide innovation, yet the limited availability of valuable lead compounds has impeded their progress in recent years. The study presents a novel molecular scaffold that exhibits remarkably potent herbicidal activity.RESULTSThrough a scaffold‐hopping strategy, a highly potent lead compound for herbicides, namely 3‐(2‐pyridinyl)‐benzothiazol‐2‐one, was unexpectedly discovered during attempts to structurally modify haloxyfop, a commercial aryl‐oxy‐phenoxy‐propionate herbicide. To investigate the structure–activity relationship (SAR) of the newly discovered herbicidal chemicals, a series of 2‐(2‐oxo‐3‐(pyridin‐2‐yl)‐2,3‐dihydrobenzo[d]thiazol‐6‐yloxy)propanoic acid derivatives, I‐01 ~ I‐27, were designed and synthesized. SAR analysis revealed that trifluoromethyl at the 5‐position of pyridine is crucial for herbicidal activity, whereas additional fluorine or Cl atom at the 3‐position of pyridine significantly enhances activity. Carboxylic ester derivatives exhibit superior herbicidal activity compared with amide derivatives. Moreover, the activity of carboxylic ester derivatives decreases with C chain extension, but the introduction of O atoms in the side chain benefits activity enhancement. Pot experiments conducted in a glasshouse demonstrated that I‐01 and I‐09 exhibited potent postemergence herbicidal activity against broadleaf weeds, and completely inhibited growth of Amaranthus retroflex, Abutilon theophrasti and Portulaca oleracea at a dosage of 75 g ha−1.CONCLUSIONDespite the initial goal of scaffold‐hopping not being achieved, we have successfully identified a novel molecular scaffold exhibiting exceptional herbicidal activity, thereby presenting innovative prospects for herbicide development. © 2024 Society of Chemical Industry.