Asymmetric cyclopropanation catalyzed by C 2-symmetric bis-(ephedrine)-Cu(II) complexes

Abstract

The asymmetric cyclopropanation of styrene with alkyl diazoacetate was performed with a series of Cu(II) complexes of novel chiral ligands, which were derived from substitution of 1,3-dibromopropane, 1,2-dibromoethane, α,α′-dibromo- m-xylene and 2,6–bis(bromomethyl)pyridine with 1 R, 2 S-(−)-ephedrine. These prepared catalysts shown to be highly active in the enantioselective cyclopropanation with ee higher than 89% under the optimal conditions.