1-Acetyl-2,2-di:methyl-3-di:halovinyl-cyclopropane carboxylic ester - prepd. by UV irradiation of 2,4,4-tri:methyl-5-di:halovinyl-4,5-di:hydro-furan-3-carboxylic acid ester and used as insecticide precursor

摘要

Prepn. of dihalovinylcyclopropane-carboxylic acid esters of formula (I) comprises conversion of a novel dihalovinyl-dihydrofuran of formula (II) by illumination pref. using UV or UV-contg. light of wavelength >200 nm in the liq. or gaseous phase: (where R1 are opt. branched alkyl (pref. 1-8C) and X is Cl or Br). 2,2,5-Trimethyl-3-carbalkoxy-4-(beta, beta-dihalovinyl)-4,5-dihydro-furans of formula (VII) are new: (I) are precursors for synthetic pyrethroid insecticides. (II) and (VII) are intermediates. Compared with known processes (DT2606635 and DT2649856), the present invention gives (I) in gold yields with only small amts. of undesirable monomer and polymer formation. The starting cpds. (II) are readily prepd. and (II) is obtd. by an industrially economic process.