Al-Catalyzed Enantioselective Alkylation of α-Ketoesters by Dialkylzinc Reagents. Enhancement of Enantioselectivity and Reactivity by an Achiral Lewis Base Additive
作者:Laura C. Wieland、Hongbo Deng、Marc L. Snapper、Amir H. Hoveyda
DOI:10.1021/ja053259w
日期:2005.11.1
An Al-catalyzed enantioselective method for additions of Me2Zn and Et2Zn 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.