Structure-activity relationships of 1,2,3-benzothiadiazole insecticide synergists as inhibitors of microsomal oxidation

The activities of 47 substituted 1,2,3-benzothiadiazoles as inhibitors of microsomal epoxidation and/or hydroxylation in enzyme preparations from rat liver or armyworm (Spodoptera eridania) gut have been evaluated. Many were found to be effective inhibitors of microsomal oxidation, the most active being the 6-butyl and 6-propoxy derivatives with I₅₀ values of 4.9 × 10^?7 and 7.0 × 10^?7M, respectively, for the epoxidation reaction. Regression analyses have established that activity of the 5-, 6-, and 5,6-substituted compounds can be satisfactorily described in equations in terms of π², π, and σ whereas that of the 4-substituted derivatives depends on π and the steric parameter E₈.