SYNTHESIS AND BIOLOGICAL-ACTIVITY OF 1,2,4-THIADIAZOLINES .3. SYNTHESIS AND INSECTICIDAL ACTIVITY OF DELTA(4)-1,2,4-THIADIAZOLIN-3-ONES

2,5-Diphenyl-Delta(4)-1,2,4-thiadiazolin-3-ones were synthesized and their insecticidal activities were examined. These compounds exhibited the disruption of larval molting and ovicidal actions, similar to the function of benzoylphenylurea insecticides. Substituent effect of the benzene ring on the insecticidal activity was similar to that of benzoylphenylureas. The introduction of fluorine atom into the aniline moiety markedly enhanced the activity. The potency of the insecticidal activities of Delta(4)-1,2,4-thiadiazolin-3-ones against the larvae of Pseudaletia separata and Spodoptera litura were almost the same as benzoylphenylureas, but their ovicidal activity against S. litura was lower than that of benzoylphenylureas. 2,5-Diphenyl-Delta(4)-1,2,4-oxadiazolin-3-ones were also synthesized, and their insecticidal activity decreased compared with those of Delta(4)-1,2,4-thiadiazolin-3-ones. Metabolism of a Delta(4)-1,2,4-thiadiazolin-3-one derivative was investigated by feeding the compound to S. litura and a benzoylphenylurea derivative was detected as a metabolite in the homogenized insect one day after the feeding. This result may suggest that Delta(4)-1,2,4-thiadiazolin-3-ones were partly metabolized into benzoylphenylureas in the insect body and consequently exhibited the insecticidal activity.