Diastereoselective silacyclopropanations of functionalized chiral alkenes
Diastereoselective silacyclopropanations of functionalized chiral alkenes
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DOI：
10.1021/ja020183k
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发表时间：
2002-06-12
影响因子：
15
通讯作者：
Woerpel, KA
中科院分区：
文献类型：
--
作者：
Driver, TG;Franz, AK;Woerpel, KA
二叔丁基二氯硅烷的锂还原和热硅烯转移（105−125 °C）是一系列功能化手性烯烃的高度非对映选择性硅杂环丙烷化的补充方法，以提供复杂的硅环。我们已经证明，官能化环己烯、环戊烯、降冰片烯和 1,1-二取代烯烃可进行硅杂环丙烷化，具有优异的非对映选择性（92:8 至 >99:1）。我们的结果表明，空间相互作用，而不是氧导向效应，控制着亚甲硅基或类甲硅中间体与烯烃的接近。我们认为，二叔丁基亚甲硅基物质的空间要求性质阻碍了与氧官能团的配位。热硅烯转移条件表现出广泛的官能团耐受性；然而，亚硅基转移的高温不能用于取代的环己烯和1,1-二取代的烯烃的硅杂环丙烷化。所得到的官能化硅杂环丙烷的精制提供了一条生产多氧化产品的有效途径。
Lithium reduction of di-tert-butyldichlorosilane and thermal silylene transfer (105−125 °C) are complementary methods for the highly diastereoselective silacyclopropanations of a range of functionalized chiral olefins to afford complex silacycles. We have shown that functionalized cyclohexenes, cyclopentenes, norbornenes, and 1,1-disubstituted alkenes undergo silacyclopropanation with excellent diastereoselectivity (92:8 to >99:1). Our results demonstrate that steric interactions, rather than oxygen-directing effects, control the approach of the silylene or silylenoid intermediate to the olefin. We believe that the sterically demanding nature of the di-tert-butylsilylene species prevents coordination to the oxygen functionality. Thermal silylene transfer conditions exhibit broad functional group tolerance; the elevated temperatures for silylene transfer, however, cannot be employed for the silacyclopropanation of substituted cyclohexenes and 1,1-disubstituted alkenes. Elaboration of the resulting functionalized silacyclopropanes provides an efficient route to polyoxygenated products.