Asymmetric Cyclopropanation Catalyzed byC2-Symmetric Ureas

Abstract

The organocatalytic asymmetric cyclopropanation of β,γ-unsaturated α-keto esters 2 with stabilized sulfur ylides 3 using C 2-symmetric bisurea 1 as a hydrogen bond catalyst has been described. The reaction provides access to 1,2,3-trisubstituted cyclopropane derivatives 4 in moderate to good yields with moderate enantio­selectivity (er up to 90:10). Interaction of both substrates and the product with the catalyst through hydrogen bonding has been supported by NMR spectroscopy studies.