INSECTICIDAL THIOUREAS - PREPARATION OF [PHENOXY-4-H-3]DIAFENTHIURON, THE CORRESPONDING CARBODIIMIDE, AND RELATED-COMPOUNDS

The high insecticidal and acaricidal activity of N-tert-butyl-N'-(2,6-diisopropyl-4-phenoxyphenyl)-thiourea (diafenthiuron) prompted the development of a procedure for radiosynthesis of this sterically hindered thiourea and two of its photoproducts and metabolites, the corresponding carbodiimide and urea. N-[4-(4'-Bromophenoxy)-2,6-diisopropylphenyl]-N'-tert-butylurea in ethyl acetate was subjected to debromination with tritium gas over palladium to obtain the [phenoxy-4-H-3]urea (24 Ci/mmol). Treatment of the labeled urea with phosphorus pentoxide in pyridine yielded the [phenoxy-4-H-3]-carbodiimide, which was then converted to [phenoxy-4-H-3] diafenthiuron on addition of hydrogen sulfide. These H-3-labeled compounds of high specific activity are of interest in defining the mechanisms of photochemical and metabolic degradation of diafenthiuron and the potential involvement of carbodiimide-binding proteins in the toxic action.