Catalytic, Enantioselective Aldol Additions with Methyl and Ethyl Acetate O-Silyl Enolates: A Chiral Tridentate Chelate as a Ligand for Titanium(IV)
作者:Erick M. Carreira、Robert A. Singer、Wheeseong Lee
DOI:10.1021/ja00098a065
日期:1994.9
Asymmetric catalysis of the Mukaiyama aldol reaction has been reported with complexes derived from Al, B, Sn(II), and Ti(IV). The levels of asymmetric induction for the addition of propionate-, isobutyrate-, and acetate-derived silyl thioketene acetals to aldehydes parallel those obtained with chiral-auxiliary-based methodologies. However, silyl ketene acetals derived from O-alkyl acetates uniformly
据报道,Mukaiyama 醛醇反应的不对称催化作用是使用衍生自 Al、B、Sn(II) 和 Ti(IV) 的配合物。将丙酸、异丁酸和乙酸衍生的甲硅烷基硫酮烯缩醛添加到醛中的不对称诱导水平与使用基于手性助剂的方法获得的水平相似。然而,衍生自 O-烷基乙酸酯的甲硅烷基乙烯酮缩醛均匀地提供了具有较低水平不对称诱导的醛缩醇。我们启动了一项旨在设计和合成手性 Ti (IV) 配合物的研究,该配合物可催化 O-三甲基甲硅烷基、O-甲基和 O-乙基乙烯酮缩醛与醛的对映选择性 Mukaiyama 醛醇。我们在此报告了一种催化剂,该催化剂由衍生自 3、Ti(O'^iPr)_4 和 3,5-二叔丁基水杨酸的三齿配体组成。