Chiral amplification based on enantioselective dual-phase distribution of a scalemic bisoxazolidine catalyst

A readily available bisoxazolidine ligand was found to catalyze the asymmetric alkylation of aldehydes with Et2Zn and less reactive Me2Zn, providing high yields and ee's in both reactions. The bisoxazolidine-catalyzed alkylations and alkynylation of benzaldehyde show a positive nonlinear effect that cannot be accounted for by Kagan's MLn model. The chiral amplification originates from selective phase distribution favoring enrichment of the major enantiomer of the scalemic catalyst in solution.