spiro [2,2]-pentane ring is a structural fragment of many biologically active compounds , including highly efficient insecticides . In the recent years, strong physiological activity has been revealed in the series of conjugated spiro [2,2]-pentane carboxylic acid esters derivatives, and interest in these compounds has increased considerably . Almost all known syntheses of such rings are based on a combination of -unsaturated carbonyl derivatives and in situ generated gem-dichlorocarbene to generate gemdichlorocyclopropane derivatives which further undergo annealation to give spiropentane carboxylic acid derivatives. Indeed, gem-dihalocyclopropane derivatives are useful synthetic intermediates because they can be readily transformed into cyclic, acyclic, heterocyclic and macrocyclic compounds including natural product precursors .