Stereospecific and regioselective reactions of silacyclopropanes with carbonyl compounds catalyzed by copper salts: Evidence for a transmetalation mechanism
Stereospecific and regioselective reactions of silacyclopropanes with carbonyl compounds catalyzed by copper salts: Evidence for a transmetalation mechanism
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DOI：
10.1021/ja982897u
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发表时间：
1999-02-10
影响因子：
15
通讯作者：
Woerpel, KA
中科院分区：
文献类型：
--
作者：
Franz, AK;Woerpel, KA
在温和的条件下(10mol%金属盐，小于或等于22℃)，硅环丙烷与羰基化合物以立体专一性和高度立体、区域和化学选择性的方式反应，在大多数情况下，CuI或CuBr2是最好的催化剂，尽管在少数例子中，ZnBr2效果相当好，插入时保持构型，对于烯和甲酰胺，在新形成的立体中心具有高的非对映选择性。对于非对称衬底，插入发生在更多取代的碳-硅键上，具有完全的区域选择性。竞争实验表明，甲酰胺的反应速度快于烯醛，后者的反应速度快于烯酸酯；饱和的醛不发生插入。用顺式二取代硅烷环丙烷，观察到硅烯转移产物。碳基插入的立体化学、区域化学和化学选择性以及硅烯转移过程可以用硅到铜的转金属反应机理来解释。
Silacyclopropanes reacted with carbonyl compounds under mild conditions (10 mol % metal salt, less than or equal to 22 degrees C) in a stereospecific and highly stereo-, regio-, and chemoselective fashion, in most cases, CuI or CuBr2 were the optimal catalysts although ZnBr2 worked comparably well in a few examples, insertion occurred with retention of configuration and, in the case of enals and formamides, with high diastereoselectivity at the newly formed stereogenic centers. For unsymmetrical substrates, insertion occurred at the more substituted carbon-silicon bond with complete regioselectivity. Competition experiments demonstrated that formamides reacted faster than enals, which reacted faster than enoates; saturated aldehydes did not undergo insertion. With a cis-disubstituted silacyclopropane, products of silylene transfer were observed. The stereochemistry, regiochemistry, and chemoselectivity of carbonyl insertion as well as the silylene transfer processes can be explained by a mechanism involving transmetalation of silicon to copper.