Department of Chemistry, University of California-Berkeley, CA 94720, USA.
Science. 2011 Dec 23;334(6063):1681-4. doi: 10.1126/science.1213918.
The discovery of distinct modes of asymmetric catalysis has the potential to rapidly advance chemists' ability to build enantioenriched molecules. As an example, the use of chiral cation salts as phase-transfer catalysts for anionic reagents has enabled a vast set of enantioselective transformations. Here, we present evidence that a largely overlooked analogous mechanism wherein a chiral anionic catalyst brings a cationic species into solution is itself a powerful method. The concept is applied to the enantioselective fluorocyclization of olefins with a cationic fluorinating agent and a chiral phosphate catalyst. The reactions proceed in high yield and stereoselectivity, especially considering the scarcity of alternative approaches. This technology can in principle be applied to the large portion of reaction space that uses positively charged reagents and reaction intermediates.
不对称催化模式的发现有可能迅速提高化学家构建对映富集分子的能力。例如，手性阳离子盐作为相转移催化剂用于阴离子试剂，已经实现了大量的对映选择性转化。在这里，我们提供的证据表明，一个在很大程度上被忽视的类似机制，其中手性阴离子催化剂将阳离子物种带入溶液中，本身就是一种强大的方法。该概念应用于阳离子氟化剂和手性磷酸催化剂与烯烃的对映选择性氟环化反应。该反应以高产率和立体选择性进行，特别是考虑到缺乏替代方法。该技术原则上可以应用于使用带正电荷的试剂和反应中间体的大部分反应空间。
