Light-dependent herbicidal activity of 4-pyridone-3-carboxanilide derivatives against Echinochloa oryzicola

Novel 4‐pyridone‐3‐carboxanilide derivatives containing various substituents on the anilide benzene and 4‐pyridone rings were synthesized, and their herbicidal activity against Echinochloa oryzicola was evaluated. These compounds exhibited light‐dependent herbicidal activity, except for some 1‐N‐benzyl analogs substituted on the anilide moiety which were light‐independent. Among compounds synthesized, 5‐bromo‐2′,6′‐diethyl‐1,4‐dihydro‐2,6‐dimethyl‐4‐oxo‐1‐phenethylpyridine‐3‐carboxanilide was found to possess the highest light‐dependent herbicidal activity, being almost equivalent with that of oxyfluorfen. The effects of substituents of the anilide benzene and 4‐pyridone rings on the activity are discussed.