Synthesis and insecticidal activity of novel 1,3,4-oxadiazolin-5-one and pyrazolin-5-one derivatives

A series of novel 2-(2,4,6-trisubstituted phenyl)-1,3,4-oxadiazolin-5-one d erivatives and 3(2,4,6-trichlorophenyl)pyrazolin-5-one derivatives were syn thesized and evaluated for insecticidal activity. It was found that a moder ately bulky alkyl group, such as a tert-butyl group, on the heterocyclic ri ng, and a trifluoromethyl group on the benzene ring were optimal substituen ts on the molecule. The oxygen atom in the oxadiazoline ring was essential for insecticidal activity. Of the compounds assayed, 4-tert-butyl-2-(2,6-di chloro-4-trifluoromethylphenyl)-1,3,4-oxadiazolin-5-one gave the highest ac tivity against Nephtotettix cincticeps, with an LC50 value of 0.51 mg litre (-1). (C) 1999 Society of Chemical Industry.