ENANTIOFACE-DIFFERENTIATING (ASYMMETRIC) ADDITION OF ALKYLLITHIUM AND DIALKYLMAGNESIUM TO ALDEHYDES BY USING (2S,2'S)-2-HYDROXYMETHYL-1-[(1-ALKYLPYRROLIDIN-2-YL)-METHYL]PYRROLIDINES AS CHIRAL LIGANDS

Asymmetric addition of alkyllithium and dialkylmagnesium to aldehydes was investigated by using the chiral amino alcohols 2, derived easily from (S)-proline, as ligands. High optical yields (45-95%) of secondary alcohols were achieved by the reaction of alkyllithium (alkyl = ethyl, n-propyl, and n-butyl) and aldehydes in a 1: 1 mixture of dimethoxymethane and dimethyl ether at -123 °C. In the reaction of methyllithium and benzaldehyde, bulkiness of the substituents, R1 and R2, in the ligand 2 remarkably affected the optical purity, and 1-phenylethanol was obtained in 86% optical yield by employing 2d (R1 = H; R2 = n-Pr) as a chiral ligand. Similarly, (R)-alcohols were obtained in 22-92% optical yields by the reaction of dialkylmagnesium and aldehydes in toluene at -110 °C. © 1979, American Chemical Society. All rights reserved.