Al-catalyzed enantioselective alkylation of alpha-ketoesters by dialkylzinc reagents. enhancement of enantioselectivity and reactivity by an achiral Lewis base additive.
An Al-catalyzed enantioselective method for additions of Me(2)Zn and Et(2)Zn to alpha-ketoesters bearing aromatic, alkenyl, and alkyl substituents is disclosed. Transformations are promoted in the presence of a readily available amino acid-based ligand and afford the desired products in excellent yields and in up to 95% ee. Investigations described illustrate that the presence of a Lewis basic additive can lead to significant enhancements in efficiency and enantioselectivity. A mechanistic model that provides a rationale for such effects is provided.
Wieland
Laura C
LC
Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, MA 02467, USA.
Deng
Hongbo
H
Snapper
Marc L
ML
Hoveyda
Amir H
AH
D000438:Alcohols / Q000138:chemical synthesis*; D000478:Alkylation; D000535:Aluminum / Q000737:chemistry*; D002384:Catalysis; D004952:Esters; D007202:Indicators and Reagents; D007659:Ketones / Q000737:chemistry*; D013237:Stereoisomerism; D015032:Zinc
D000438:Alcohols; D004952:Esters; D007202:Indicators and Reagents; D007659:Ketones; D000535:Aluminum; D015032:Zinc