Abstract
An enantioselective cyclopropanation of a-substituted a,b-unsaturated aldehydes with bromomalonate has been successfully developed through a domino Michael/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 a,b-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.