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Highly Enantioselective Epoxidation of cis-Alkenylsilanes

机译：顺烯基硅烷的高度对映选择性环氧化

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Since the development of the titanium/tartrate-catalyzed asymmetric epoxidation of allyl alcohols in 1980, significant progress has been made in the field of asymmetric epoxidation of olefins, and now most olefins can be transformed to epoxides with high optical purity.[1–3] However, there are no satisfactory methods available thus far for the asymmetric epoxidation of terminal olefins such as styrene.[4] While epoxysilanes are a synthetic equivalent of epoxides, a highly enantioselective epoxidation of simple alkenylsilanes is also quite rare in the literature.[5, 6] Although Shi and co-workers applied their sugar-derived ketone catalyst to the epoxidation of 2,2-disubstituted alkenylsilanes and obtained the epoxysilanes with high enantioselectivity up to 94% ee, the method has a major drawback that it requires a substoichiometric amount of the catalyst.[7, 8] While the introduction of a sterically more demanding silyl group at the vinyl position is expected to further facilitate the enantioface-differentiation,there is a concern that the steric hindrance strongly inhibits the reaction progress.[5] Thus, in order to implement the catalytic asymmetric epoxidation of alkenylsilanes, the utilization of a more refined epoxidation catalyst in terms of catalytic activity, asymmetric induction and durability is necessary.
机译：自1980年钛/酒石酸催化烯丙醇的不对称环氧化反应发展以来，在烯烃的不对称环氧化反应领域取得了重大进展，现在大多数烯烃都可以转化为具有高光学纯度的环氧化物。[1-3] ]然而，迄今为止，尚无令人满意的方法可用于末端烯烃（如苯乙烯）的不对称环氧化。[4]尽管环氧硅烷是环氧化物的合成等同物，但简单的烯基硅烷的高度对映选择性环氧化在文献中也很少见。[5，6]尽管Shi和同事将其糖衍生的酮催化剂应用于2,2-的环氧化二取代的链烯基硅烷，并获得高对映体选择性高达ee达94％的环氧硅烷，该方法的主要缺点是需要亚化学计量的催化剂。[7，8]在乙烯基位置引入空间上要求更高的甲硅烷基有望进一步促进对映体的分化，人们担心空间位阻会强烈抑制反应进程。[5]因此，为了实现烯基硅烷的催化不对称环氧化，就催化活性，不对称诱导和耐久性而言，需要使用更精制的环氧化催化剂。

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