Highly efficient conjugate addition of diethylzinc to enones catalyzed by chiral ligands derived from (S)-mandelic acid

Diastereomerically pure heteroorganic catalysts built on the chiral scaffold of (S)-(+)-mandelic acid and containing secondary hydroxyl and aziridine moieties, have proven to be highly efficient for the enantioselective conjugate diethylzinc addition to chalcone and 2-cyclohexen-1-one to afford the desired chiral adducts in high yields (up to 92%) and with ee’s of up to 90%. The influence of the stereogenic center located at the aziridine moiety on the stereochemical outcome is also discussed.