Quantitative structure‐activity study of insecticidal 2‐methoxy‐5‐(substituted‐phenyl)‐1, 3, 2‐oxazaphospholidine 2‐sulfides against Musca domestica L. by topical application

Abstract

AbstractThe quantitative relationship between the structure of 2‐methoxy‐5‐(substituted‐phenyl)‐1, 3, 2‐oxazaphospholidine 2‐sulfides (5‐PMOS) and their insecticidal activity against the house fly. Musca domestica L., was analyzed using reported physicochemical parameters and regression analysis. The electronic nature of the substituent on the phenyl group of 5‐PMOS has the most significant effect on the activity, followed by hydrophobic and steric effects; the optimum value of Σρ is zero and the more hydrophobic the substituents on the phenyl group, the higher the insecticidal activity. The plots of observed pLD50, values against calculated pLD50 values for compounds having substituents in the ortho‐position deviated downwards from those of compounds having substituents at the meta and/or para positions. This ortho‐effect, which reduces the insecticidal activity of compounds having substituents at the ortho‐position, was expressed by a dummy parameter D, which has the value 2 for di‐ortho‐substituted derivatives, 1 for mono‐ortho‐substituted derivatives and zero for others. Thus, the highest activity was obtained for 2‐methoxy‐5‐phenyl‐1, 3, 2‐oxazaphospholidine 2‐sulfide, and the activity was decreased by the introduction of any substituents on the phenyl group.