Enantioselective alkylation of aldehydes with diethylzinc catalyzed by C-2-symmetric ligands

The C-2-symmetric pyridine 1, incorporating two units of (-)-ephedrine, is an effective catalyst for the enantioselective reactions of diethylzinc with a series of aromatic aldehydes. The propanol products possess the S-configuration. This result is a significant reversal of stereochemistry based upon literature precedents and our direct comparisons with reactions catalyzed by the corresponding C-2-symmetric xylene 2.