Asymmetric Michael Reactions on Polymeric Support: Auxiliary Immobilization and Stereoselective Construction of Quaternary Stereocenters
作者:Burkard Kreidler、Angelika Baro、Jens Christoffers
DOI:10.1002/ejoc.200500450
日期:2005.12
Merrifield resin and on poly(ethylene glycol) are reported. The latter is shown to work excellently in asymmetric copper(II)-catalyzed Michael reactions of cyclic β-oxo esters 2 with methyl vinyl ketone (4), yielding the corresponding addition products 5 with quaternary stereocenter in selectivities of 97–99 % ee. The PEG-supported auxiliary 1d can be precipitated from diethyl ether solutions and reused
报道了将 L-缬氨酸衍生的辅助剂固定在 Merrifield 树脂和聚 (乙二醇) 上的几种策略。后者在不对称铜 (II) 催化的环状 β-氧代酯 2 与甲基乙烯基酮 (4) 的迈克尔反应中表现出色,以 97-99% ee 的选择性产生相应的加成产物 5,其具有季立体中心。PEG 支持的助剂 1d 可以从乙醚溶液中沉淀出来并重复使用。通过 DMAP 催化的酯交换方法以 92% 的产率制备含硫 β-氧代酯 2c,以检测固体载体上的烯胺形成。硫含量可用作燃烧分析中的附加参数,因此可用作烯胺形成的诊断探针。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,