Hydroxyamides versus amino alcohols in the enantioselective addition of diethylzinc to benzaldehyde

Abstract

Two series of structurally related enantiopure isoborneols (10-amino- and 10-amino-10-oxoisoborneols) have been obtained from ketopinic acid and compared as chiral ligands for the enantioselective addition of diethylzinc to benzaldehyde in the absence of Ti(O- i-Pr) 4. The results obtained (chemical yields and enantiomeric excesses) show that identical structural factors (functionalization grade and symmetry group) exert very different effects on both series. The observed differences have been rationalized on the basis of the coordination ability of each ligand type to form the corresponding reactive zinc-chelate catalyst.