Optimized synthesis of 2-substituted 1-halocyclopropane-1-carboxylic acids

Abstract

The reaction of gem-dichloro- and gem-dibromocyclopropanes with n-butyllithium in THF under argon at–78°С followed by purging the reaction mixture with dry CO₂ was used to synthesize cis- and/or trans-1-halocyclopropane-1-carboxylic acids in 30–56% yields. The yields of the target products could be increased to 76–83% by the addition of an equimolar amount of LiCl to the reaction mixture. The highest salt effect was obtained with lithium chloride generated in situ (88–96%).