Synthesis of novel hygienic pyrethroid compounds based on momfluorothrin

The synthesis of novel structured active compounds is of great significance for the management of mosquito resistance to insecticides. In this study, based on momfluorothrin, 17 novel pyrethroid compounds were designed and synthesized, all of which were structurally confirmed by mass spectrometry and nuclear magnetic resonance spectroscopy. Cylinder tests of mosquito coil biological activity revealed that five of these compounds (2,3,5,6-tetrafluoro-4-methoxymethylbenzyl(1R,3R)-3-((Z)-2-cyanovinyl)-2,2-dimethylcyclopropanecarboxylate (1a), 2,3,5,6-tetrafluorobenzyl(1R,3R)-3-((Z)-2-cyanovinyl)-2,2-dimethylcyclopropanecarboxylate (2a), 2,3,4,5,6-pentafluorobenzyl(1R,3R)-3-((Z)-2-cyanovinyl)-2,2-dimethylcyclopropanecarboxylate (3a), 2,3,5,6-tetrafluoro-4-methylbenzyl(1R,3R)-3-((Z)-2-cyanovinyl)-2,2-dimethylcyclopropanecarboxylate (4a), and 3-phenoxy-4-fluorobenzyl(1R,3R)-3-((Z)-2-cyanovinyl)-2,2-dimethylcyclopropanecarboxylate (11)) exhibited better knockdown activity against Culex pipiens pallens than tetramethylfluthrin and momfluorothrin, with compound 2a showing the highest activity KT₅₀ = 4.61 min, 0.05% (m/m). Further cylinder test of the 0.9% compound 2a liquid vaporizer showed that its knockdown activity (KT₅₀ = 4.56-4.98 min) was comparable to that of commercially available 0.31% dimefluthrin-based and 1.5% tetramethylfluthrin-based products, and its analogous site activity was slightly superior to that of the 0.31% dimefluthrin-based product. Acute toxicity tests of compound 2a indicated that it is slightly toxic to rats in terms of acute oral toxicity, acute percutaneous toxicity, and acute inhalation toxicity with LD₅₀ values > 5000 mg/kg (bw). The favorable activity and low toxicity of compound 2a make it more suitable for the development of low-toxicity liquid vaporizer.