A systematic study of chiral homoprolinols and their derivatives in the catalysis of enantioselective addition of diethylzinc to aldehydes

Homoprolinol analogs, a class of optically active γ‐amino alcohols, were examined systematically in the enantioselective addition reactions of diethylzinc to aldehydes. By comparison of the results catalyzed by these γ‐amino alcohols with those by the β‐amino alcohols based on pyrrolidine architecture reported in the literature references, we have observed that the γ‐amino alcohols are superior to the corresponding β‐amino alcohols when the nitrogen and the oxygen are unsubstituted. Among the homoprolinols we tested, 2b gave the best results (45–88% yields, 44–81% ee) in the addition reactions. To the best of our knowledge, 2b has been noticed as one of the most efficient γ‐amino alcohol catalysts based on pyrrolidine framework. Chirality, 2011. © 2011 Wiley‐Liss, Inc.