Synthesis of enantiomerically enriched amines by chiral ligand mediated addition of organolithium reagents to imines

The effect of the imine and ligand structure on the enantioselective addition of organolithiums to imines has been studied. Thus, (?)-sparteine-mediated additions of MeLi and/or n-BuLi to p-anisidine derived phenylimine 1a afforded the corresponding amines with modest e.e.s. The use of bulkier or more reactive imines (naphthyl or tosyl imines) resulted in loss of enantioselectivity. The best enantioinduction with this ligand was obtained with enolizable imines 8 and 10. When bis(oxazolidines) were used as chiral ligands, a strong influence of their structure in the enantioselectivity of the addition of MeLi and n-BuLi to phenylimine 1a was observed.