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Despite the enormous progress made in the asymmetric addition of nucleophiles to prochiral carbonyl compounds for the preparation of chiral alcohols, the corresponding study of enantioselective conversion of prochiral azomethine functions to chiral amines remains a relatively undeveloped area of research. This account reviews the current state of this new field of investigation.

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The enantioselective addition of organolithium reagents to N-anisyl aldimines promoted by chiral bisoxazolines and (−)-sparteine as external ligands is described. This reaction proceeds readily with a wide range of aldimine substrates (aliphatic, aromatic, olefinic) and organolithium nucleophiles (Me, n-Bu, Ph, vinyl) in excellent yields (81-99%) and with high enantioselectivities (up to 95.5:4.5 er). The external ligands can be used in substoichiometric amounts albeit with slightly attenuated enantioselectivities. A systematic evaluation of the structural features of the bisoxazolines revealed a primary contribution from the substituent at C(4) and a secondary influence from the bridging substituents. A computational analysis (PM3) provided a clear rationalization for the origin of enantioselectivity.