This paper describes the design and application of new
binaphthyl-proline-based
chiral ligands bearing imidazoline functional groups. These chiral
ligands incorporate the advantages of both the binaphthyl and proline
skeletons, they are featured with regulatable electronic and steric
properties for the imidazoline functional groups, and form chiral
complexes with different metal salts such as cuprous acetate. In the
presence of an appropriate amount of a chiral catalyst, enantioselective
conjugate addition of 4-hydroxycoumarin or related nucleophiles to
different β,γ-unsaturated α-ketoesters proceeded
readily, giving the desired products in high yield (up to 99%) and
excellent enantiomeric excess (up to 99%).