Catalyzed Enantioselective Alkylation of Aldehydes

Enantioselective alkylation of a variety of aldehydes with diethylzinc was achieved by using catalytic amounts of optically active pyridines and C 2 ‐symmetric 2,2′‐bipyridines. The products were obtained in good yields with high enantioselectivities. Steric factors of the catalyst structure which govern the stereoselectivity were revealed, and important reaction intermediates were identified by spectroscopic means and singlecrystal X‐ray diffraction. The effect of additives on the optical purity of the product was studied. A strong asymmetric amplification was found with catalysts of low ee′s.