Design and synthesis of a tridentate ligand for asymmetric bifunctional catalysis

Covalent attachment of a quinine moiety to a Schiff base ligand through an ester linkage generates a novel tridentate ligand that gives a new Lewis acid–Lewis base (LA–LB∗) bifunctional catalyst having a mixture of the LA configurations. The LB∗-dependent asymmetric bifunctional catalysis was demonstrated using the addition of diethylzinc to 2-methoxybenzaldehyde as a test reaction and the substrate scope of the new catalyst was illustrated using aromatic aldehydes.