Kazuo Yagi

Synthesis and insecticidal/acaricidal activity of novel 3-(2,4,6-trisubstituted phenyl)uracil derivatives.

A series of novel 3-(2,4,6-trisubstituted phenyl)uracil derivatives has been synthesised and assayed for insecticidal/acaricidal activity. The assay indicated certain requirements for optimal insecticidal activity, which can be summarised as follows: (a) the substituents on the phenyl ring should possess hydrophobicity and electron-withdrawing properties, and the sum of their volumes determines the level of activity; (b) the substituent at the 6-position on the uracil ring should also possess electron-withdrawing properties and hydrophobicity, together with the correct volume; (c) the 1-position on the uracil ring should be unsubstituted for activity against Nephotettix cincticeps and Epilachna vigintioctopunctata, but substituents with length C3 to C4 may be optimal for activity against Tetranychus urticae; (d) certain substituents at the 5-position of the uracil ring give activity against E vigintioctopunctata and T urticae, but not against N cincticeps; (e) a thiocarbonyl group at the 2-position of the uracil ring is less effective than a carbonyl group. Of the compounds assayed, 3-(2,6-dichloro-4-trifluoromethylphenyl)-6-trifluoromethyluracil showed high activity against all the species assayed. © 2000 Society of Chemical Industry

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 derivatives and 3-(2,4,6-trichlorophenyl)pyrazolin-5-one derivatives were synthesized and evaluated for insecticidal activity. It was found that a moderately bulky alkyl group, such as a tert-butyl group, on the heterocyclic ring, and a trifluoromethyl group on the benzene ring were optimal substituents 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-dichloro-4-trifluoromethylphenyl)-1,3,4-oxadiazolin-5-one gave the highest activity against Nephotettix cincticeps, with an LC 50 value of 0.51 mg litre -1 .