Several new chiral bipyridyldiol ligands that promote the chromium-catalyzedenantioselective addition of allylic halides to aldehydes in up to 99% ee were synthesized. The chromium-catalyzed allylation of aldehydes using ligands 4 and 4a in the presence of chromium(III) chloride and allyl chloride provided the highest enantioselectivity.
Chiral Aryl Pyridyl Alcohols as Enantioselective Catalysts in the Addition of Diethylzinc to Substituted Benzaldehydes
作者:Tien-Chu Chang、Chinpiao Chen
DOI:10.1002/jccs.200800088
日期:2008.6
(1/R)-(+)-α-pinene (> 97% ee), and applied in the enantioselective addition of diethylzinc to substitutedbenzaldehydes, to yield alcohols with the (S)-configuration with an enantiomeric excess that typically ranges from 19 to 86%. Importantly, the electron-withdrawing substituents at the meta-position of the substitutedbenzaldehydes exhibited high enantioselectivity during alkylation using diethylzinc