Synthesis and Insecticidal Activity of Silicon-containing Pyrethroids with Low Fish Toxicity

Abstract

In the course of study on new pyrethroids, it was found that organosilicon compounds substituted with silicon atom at the quaternary carbon atom of ethofenprox were showed pyrethroidal insectactivity. Among them dimethyl (4-ethoxyphenyl) silylmethyl-3-phenoxybenzyl ether (SSI-116) was selected as the most potent candidate, which has broad-spectrum insectactivity, extremely low fish toxicity and low mammalian toxicity. The comparison between SSI-116 and ethofenprox in various biological activity to insects suggested that SSI-116 acted as a bioisostere of ethofenprox against insects and was classified to type I pyrethroids. But in fish toxicity the large difference between them was observed, that is the LC₅₀ value for carp of SSI-116 and ethofenprox were >562ppm and 5.0ppm, respectively. In the field trials SSI-116 was effective agent for control of pests in rice paddy field. The results suggested that sila-substitution of known pesticides might be available method for future pesticide development.