Diastereoselective nucleophilic additions to imines attached to tricarbonyl(arene)chromium moieties

Abstract

A range of imine complexes has been prepared which possess planar chirality associated with the attached tricarbonyl(1,2-disubstituted arene)chromium moiety. Nucleophilic addition to the imine group of these complexes occurs with high diastereoselectivity, providing an efficient route to the asymmetric synthesis of chiral amines. The stereochemical outcome of the additions may be rationalized in terms of a favoured conformer for the complexes, with nucleophilic attack occurring on the face of the imine anti to the sterically demanding Cr(CO)₃ group. Related studies have also been carried out on imine complexes in which the chiral auxiliary is instead a carbon centre attached to the imine N atom. In these latter systems high diastereoselectivity was also observed, but was not superior to that achieved with the related free amines.