Enantioselective addition of diethylzinc to aldehydes catalyzed by N-(9-phenylfluoren-9-yl) beta-amino alcohols

A set of secondary N-phenylfluorenyl beta-amino alcohols have been prepared and evaluated as catalysts far the enantioselective addition of diethylzin c to benzaldehyde. The influence of the substituents on the stereogenic cen ters of the Ligand has been studied, and enantioselectivities up to 97% hav e been obtained. Those ligands with bulky groups in the carbinol stereocent er and small groups alpha to the nitrogen atom displayed the best catalytic activity and enantioselectivity. The most enantioselective ligand (4e) was found to possess general applicability far the enantioselective addition o f diethylzinc to a variety of aromatic and aliphatic aldehydes.