Design, synthesis and fungicidal activity of 3,4-dichloroisothiazolocoumarin-containing strobilurins

Twenty-one novel 3,4-dichloroisothiazolocoumarin-containing strobilurins were rationally designed and synthesized. Preliminary bioassay showed that compounds 7c, 7h and 7l exhibited over 80% inhibitory rate against Sclerotinia sclerotiorum at 50 μg/mL, 7c exhibited good activity against S. sclerotiorum with median effective concentration (EC₅₀) of 4.08 μg/mL, while the positive control coumoxystrobin showed EC₅₀ of 1.00 μg/mL. In addition, 7d showed better fungicidal activity with a lower EC₅₀ value of 7.65 μg/mL against Botrytis cinerea than that of positive control trifloxystrobin with its EC₅₀ value of 21.96 μg/mL. This study indicated that 3,4-dichloroisothiazolocoumarin-containing strobilurin was a promising fungicide lead deserved for further study.