L-Proline-Derived Tertiary Amino Alcohols as Chiral Ligands for Enantioselective Addition of Diethylzinc to Aldehydes

A series of L-proline derived tertiary amino alcohols was used as chiral ligands in the asymmetric addition reaction of Et2Zn to aldehydes. Among these ligands, it was found that ligand 1b which has the biggest steric and electrondonating substituent at the nitrogen position yielded the highest enantioselectivities when applied in the catalytic asymmetric addition of diethylzinc to p-chlorobenzadehyde. The experiment results of our paper may supply useful experience to help in revealing the relationship between ligand structure and ee values of the products.