(?-Cis-3-(dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid (I) was synthesized through two ways from Et 5-chloro-3,3-dimethylpentanoate (II) which had been obtained from isoprene. The intermediate 4,4-dimethyl-3,4-dihydro-2-pyranone (III) was obtained by phenylthioetherification of II, oxidation to 5-oxo-3,3-dimethylpentanoic acid, and cyclization to III or hydration and acidification of II, esterification and oxidation to Me 5-oxo-3,3-dimethylpentanoate and then cyclization to III.

Key words: SYNTHETIC PYRETHROID-INSECTICIDES, CYCLOPROPANE CARBOXYLIC ACID P, DICHLOROETHYLENE P, CHRYSANTHEMIC