Enantioselective addition of diethylzinc to aromatic aldehydes catalyzed by C2-symmetric chiral diols

Abstract

• Optically pure C 2 -symmetric diols have been synthesized. • Chiral diols were evaluated in the enantioselective alkylation of aromatic aldehydes. • The ethylation of benzaldehyde and 1-naphthaldehyde was achieved with excellent ees. Optically pure C 2 -symmetric diols have been synthesized with moderate yields in a straightforward manner, and are used as catalysts in the enantioselective alkylation of aromatic aldehydes with diethylzinc. The addition of diethylzinc to benzaldehyde and sterically hindered 1-naphthaldehyde was achieved with excellent enantioselectivities (97–99% ee) under catalysis with (1 R ,2 R )-1,2-bis(3,5-dibromophenyl)-ethane-1,2-diol and (1 R ,2 R )-1,2-bis(3,5-diphenylphenyl)-ethane-1,2-diol.