Asymmetric Catalysis with Ethylene. Synthesis of Functionalized Chiral Enolates.
Asymmetric Catalysis with Ethylene. Synthesis of Functionalized Chiral Enolates.
复制标题
DOI：
10.1021/jacs.5b10364
复制
发表时间：
2015-11-18
影响因子：
15
通讯作者：
RajanBabu TV
中科院分区：
文献类型：
--
作者：
Biswas S;Page JP;Dewese KR;RajanBabu TV
三烷基硅烯醇醚是一种用途广泛的中间体，通常用作羰基化合物合成的烯醇酯替代物。然而，目前还没有广泛适用的催化方法来合成手性硅烯醇醚，这些方法除了硅烯醇醚部分本身的许多可能的反应之外，还具有潜在的功能。在这里，我们报告了高催化（底物：催化剂比高达1000:1）和对映选择性（92%至98%的主要对映体）的合成过程，这些化合物在β-位置的手性碳上有一个乙烯基。该反应在环境条件下进行，使用三烷基硅氧基-1,3-二烯和乙烯（1气氛）作为前体，并使用易于获得的（二膦）-钴（II）配合物作为催化剂。硅烯醇酯可以很容易地转化为新型的对映纯三氟乙烯酯，一类高度通用的交叉偶联试剂，使得合成其他对映纯的，立体定义的三取代烯烃中间体不容易用现有方法获得。举例说明了Kumada、Stille和Suzuki偶联反应。
Trialkylsilyl enol ethers are versatile intermediates often used as enolate surrogates for the synthesis of carbonyl compounds. Yet there are no reports of broadly applicable, catalytic methods for the synthesis of chiral silyl enol ethers carrying latent functionalities useful for synthetic operations beyond the many possible reactions of the silyl enol ether moiety itself. Here we report a general procedure for highly catalytic (substrate:catalyst ratio up to 1000:1) and enantioselective (92% to 98% major enantiomer) synthesis of such compounds bearing a vinyl group at a chiral carbon at the β-position. The reactions, run under ambient conditions, use trialkylsiloxy-1,3-dienes and ethylene (1 atmosphere) as precursors, and readily available (bis-phosphine)-cobalt(II) complexes as catalysts. The silyl enolates can be readily converted into novel enantiopure vinyl triflates, a class of highly versatile cross-coupling reagents, enabling the syntheses of other enantiomerically pure, stereo-defined trisubstituted alkene intermediates not easily accessible by current methods. Examples of Kumada, Stille and Suzuki coupling reactions are illustrated.