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.
cyclopropane - ring closure - asymmetric synthesis - asymmetric reduction - stereoselectivity