Amino acid-derived chiral imidazolium salts, each bearing a pyridine ring, were developed as N-heterocyclic carbene ligands. The copper-catalyzed asymmetric alkylation of various N-sulfonylimines with dialkylzinc reagents in the presence of these chiral imidazolium salts afforded the corresponding alkylated products with high enantioselectivity (up to 99 % ee). The addition of HMPA to the reaction mixture as a co-solvent is critical in terms of chemical yield and enantioselectivity. A wide range of N-sulfonylimines and dialkylzinc reagents were found to be applicable to this reaction.

Asymmetric 1,2-addition of dialkylzinc reagents to α,β-unsaturated N-tosylaldimines was catalyzed by copper salt in the presence of chiral imidazolium salts having a pyridine ring, which were derived from amino acid, to afford the corresponding chiral allylic amines with up to 91% ee in reasonably high yields. The chiral N-heterocyclic carbene (NHC) ligand played an important role in controlling chemoselectivity.

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