Synthesis and Herbicidal Activity of 2‐Aroxy‐propanamides Containing Pyrimidine and 1,3,4‐Thiadiazole Rings

A series of novelN‐{5‐[2‐(4,6‐dimethoxy‐pyrimidin‐2‐yloxy)‐phenyl]‐[1,3,4]thiadiazol‐2‐yl}2‐aroxy‐propanamides were designed and synthesized by the multistep reactions. 2‐(4,6‐Dimethoxy‐pyrimidin‐2‐yloxy)‐benzaldehyde (1) reacted with aminothiourea to yield2, which undergoes ring closure to give 5‐[2‐(4,6‐dimethoxy‐pyrimidin‐2‐yloxy)‐phenyl]‐[1,3,4]thiadiazol‐2‐amine (3) in the presence of ferric chloride in refluxing ethanol.3reacted with 2‐aroxy‐propionyl chlorides to give the target compounds4a,4b,4c,4d,4e,4f,4g,4h,4iin moderate to good yields. Their structures were confirmed by IR,1H‐NMR, EIMS, and elemental analyses. The preliminary bioassay indicated that some of them displayed moderate to good selective herbicidal activity againstBrassica campestris L. at the concentration of 100 mg/L. However, these compounds did not possess inhibitory activity againstEchinochloa crus‐galliat the tested concentrations.