Enantioselective alkylation of aromatic aldehydes with (+)-camphoric acid derived chiral 1,3-diamine ligands

Abstract

A series of chiral 1,3-diamine ligands derived from (+)-camphoric acid were prepared from the reaction of 1,3-diamino-1,2,2-trimethylcyclopentane with aromatic aldehydes, followed by reduction of the corresponding diimines. These newly synthesized ligands were tested in the enantioselective alkylation of benzaldehyde with diethylzinc, giving 1-phenyl-1-propanol with enantiomeric ratios of up to 86:14. Our most selective ligand, derived from 2-methoxybenzaldehyde, was also tested in the alkylation of several aromatic aldehydes and product alcohols with enantiomeric ratios of up to 93.5:6.5 being observed in 2h at room temperature in the presence of 5mol% ligand.