| abstract |
3-Halogenoethyl- or propyl-2,2-dimethylcyclopropane carboxylic acid esters, which are intermediates in the preparation of synthetic pyrethroids, are prepared by the reaction of certain halogenopentenes or hexenes with a diazoacetic ester in the presence of a catalyst which is metallic copper or a copper (II) salt, a rhodium (II) salt of a carboxylic acid or a transition metal complex of certain chiral Schiff bases. By the use of the latter class of catalysts the yield of preferred cis IR isomer may be increased relative to the other possible isomers. |