Synthesis, structures, and herbicidal activity of isoxazole derivatives

Abstract magnified image The several novel 3‐substituted phenyl isoxazole derivatives were prepared from substituted phenyl‐butan‐1,3‐dione. Their structures were confirmed by element analysis, IR, MS, and 1 H NMR. X‐ray structure analysis indicated that the dihedral angles of the phenyl ring with the isoxazole ring in compounds 4a and 4b were 19.46° and 49.18°, respectively. Preliminary bioassay showed that the title compounds had good activity to various weeds, and 4a exhibited almost the same activity with 4b . This was different from the former works, which showed that the big dihedral angle of the phenyl ring with the heterocyclic moiety was necessary for high‐herbicidal activity. J. Heterocyclic Chem., (2010).