Quantitative structure-activity relationships in insecticidal oxathiolane and dithiolane oxime carbamates and related compounds

Abstract

The insecticidal and acaricidal activities and the mammalian toxicity of a series of 28 oxathia and dithia heterocyclic oxime methylcarbamates have been related to certain of their physicochemical properties.Multiple regression studies have shown that fly head acetylcholinesterase inhibition and housefly, buckthorn aphid, two-spotted spider mite, southern armyworm, Mexican bean beetle, and rat toxicities are enhanced by increased steric requirement of ring substituents (Taft Ea). Increasing lipophilicity (log P) uniformly diminishes activity against the arthropods and the rat while the presence of a /3-sulfur as compared to a /3-oxygen is associated with increased activity against all test organisms. These correlation studies suggest that further synthesis in this series is unlikely to yield effective insecticides in which the arthropod/mammal selectivity is improved over that of compounds already in hand.The syntheses and the insecticidal properties of carbamate esters of 4-oximino-l,3-oxathiolanes (la), 3-oximino-l,4-oxathianes (lb;Kurtz et al., 1987), 4-oximino-l,3dithiolanes (Ic), and 3-oximino-l,4-dithianes (Id;D'Silva et al., 1985) have been reported separately (Chart I).These materials are broad-spectrum insecticides having excellent activity against the buckthorn aphid, Mexican bean beetle, southern armyworm, and the housefly. The dithia compounds and selected members of the oxathia series in addition exhibit good acaricidal potency. The more insecticidally active monomethylcarbamates in both series of compounds, however, possess significant levels of toxicity to warm-blooded animals as measured by acute toxicity to the rat. As part of the examination of these compounds we sought to define which structural and physicochemical features of the monomethylcarbamates in the series are significant in controlling toxicity to both insect and mammalian species. With the role of such