Process for the preparation of novel 3,3-dimethyl-4,6,6-trihalo-5-hexanoic esters and their use.

摘要

The novel esters have the formula <IMAGE> They are prepared by reacting butanolides of the formula <IMAGE> with alcohols of the formula ROH in the presence of halogenating agents. The halogenating agents used are preferably hydrohalic acids of the formula HX. The novel esters of the formula V can be converted into cyclopropane carboxylic acid derivatives of the formula <IMAGE> by reaction with a strong base. In the formulae, the symbols X denote identical or different halogen atoms, preferably chlorine, and R denotes a lower alkyl group. The compounds of the formula I are intermediates for the synthesis of pyrethrin-type insecticides.