Synthesis and fungicidal activities of (alpha-methoxybenzyl)isoxazoles

A series of (alpha-methoxybenzyl)isoxazole derivatives (I) were synthesized and their fungicidal activities were assessed. Studies of the structure-ac tivity relationship revealed the strongest fungicidal activity when the iso xazole moiety was comprised of a 3-methyl-5-isoxazolyl group. When position -2 of the phenyl ring in the benzyl moiety was substituted with a 4-phenyl- 2,3-diaza-1,3-pentadienyl group, good fungicidal activity was achieved. Whe n the benzene ring in the 4-phenyl-2,3-diaza-1,3-pentadienyl moiety was sub stituted with a 4-bromo, 4-trifluoromethoxy or 3,4-dichloro group, good fun gicidal activity was obtained. Among the 29 compounds examined, 5-[2-{4-(4- bromophenyl)-2,3-diaza-1,3-pentadienyl}alpha-methoxybenzyl]-3-methylisoxazo le (23) showed potent activities against cucumber powdery mildew and cucumb er downy mildew.