Asymmetric Synthesis of Di-and Trisubstituted Cyclopropanes through an IntramolecularRing Closure

An asymmetric synthesis of di- and trisubstituted cyclopropanes proceeding through an intramolecular ring closure of activated chiral benzyl alcohols has been developed. The chiral alcohol intermediates are obtained from asymmetric reduction of readily available 1,4-keto esters and undergo a one-pot activation and ring closure to provide the ester-functionalized cyclopropanes in high enantio- and diastereomeric purity. This methodology avoids the use of hazardous diazo and alkyl zinc reagents commonly employed in cyclopropanation reactions.