Organocatalyzed cyclopropanation of α-substituted α,β-unsaturated aldehydes: Enantioselective synthesis of cyclopropanes bearing a chiral quaternary center

Article abstract of DOI:10.1002/chem.201000334

An enantioselective cyclopropanation of α-substituted α,β-unsaturated aldehydes with bromomalonate has been successfully developed through a domino Michael/a-alkylation strategy. The method allows the efficient formation of cyclopropanes bearing a quaternary carbon stereocenter at the a-position of the aldehydes by using iminium/enamine catalysis and gives a nice extension on the organocatalytic cyclopropanation of bromomalonate and α β-unsaturated aldehydes previously reported by other groups. Very good yields (up to 81%) and enantioselectivities (up to 97% ee) have been obtained. The optically active cyclopropane derivatives are of high synthetic interest as useful targets for further elaboration into more complex structures. 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim aldehydes, cyclopropanes, domino reactions, organocatalysis, quaternary stereocenters.