Enantioselective and diastereoselective mukaiyama-Michael reactions catalyzed by bis(oxazoline) Copper(II) complexes
Enantioselective and diastereoselective mukaiyama-Michael reactions catalyzed by bis(oxazoline) Copper(II) complexes
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DOI：
10.1021/ja010302g
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发表时间：
2001-05-16
影响因子：
15
通讯作者：
Willis, MC
中科院分区：
文献类型：
--
作者：
Evans, DA;Scheidt, KA;Willis, MC
用[Cu((S，S)-t-Bu-box)](SbF_6)(2)(1a)作为Lewis酸催化剂，研究了烯醇硅烷与不饱和亚胺衍生物的高对映选择性和非对映选择性Michael加成反应。这些加成的产物是有用的合成子，含有能够在温和条件下分化的末端。Michael受体的ct面选择性与亚胺底物的两点结合是一致的，可以看作是底物对映体选择性在相应的Diels-Alder反应中的延伸。提出了一个类似于描述杂化Diels-Alder反应的模型来解释观察到的烯醇硅烷几何构型与产物绝对非对映控制之间的关系。提供了对催化剂失活模式的见解，包括在反应过程中释放的二氢吡喃中间体对催化剂抑制的光谱证据。本发明公开了一种方法，其中使用酒精添加剂来水解所述抑制二氢吡喃，并在显著缩短的反应时间内提供脱硅化的Michael加合物。
The scope of highly enantioselective and diastereoselective Michael additions of enolsilanes to unsaturated imide derivatives has been developed with use of [Cu((S,S)-t-Bu-box)](SbF6)(2) (1a) as a Lewis acid catalyst. The products of these additions are useful synthons that contain termini capable of differentiation under mild conditions. Michael acceptor ct-facial selectivity is consistent with two-point binding of the imide substrate and can be viewed as an extension of substrate enantioselection in the corresponding Diels-Alder reactions. A model analogous to the one employed to describe the hetero Diels-Alder reaction is proposed to account for the observed relation between enolsilane geometry and product absolute diastereocontrol. Insights into modes of catalyst inactivation are given, including spectroscopic evidence for inhibition of the catalyst by a dihydropyran intermediate that evolves during the course of the reaction. A procedure is disclosed in which an alcohol additive is used to hydrolyze the inhibiting dihydropyran and afford the desilylated Michael adduct in significantly shortened reaction time.