title: Al-catalyzed enantioselective alkylation of alpha-ketoesters by dialkylzinc reagents. enhancement of enantioselectivity and reactivity by an achiral Lewis base additive.
abstract: 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.
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, MA 02467, USA.
authors.forename: Laura C
authors.initials: LC
authors.lastname: Wieland
authors.forename: Hongbo
authors.initials: H
authors.lastname: Deng
authors.forename: Marc L
authors.initials: ML
authors.lastname: Snapper
authors.forename: Amir H
authors.initials: AH
authors.lastname: Hoveyda
mesh_terms: 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
chemical_list: D000438:Alcohols; D004952:Esters; D007202:Indicators and Reagents; D007659:Ketones; D000535:Aluminum; D015032:Zinc