Nature2014-06-26 5:59 PM

从简单烯烃合成手性产品 Asymmetric synthesis from terminal alkenes by cascades of diboration and cross-coupling

论文摘要 

这篇论文介绍了一个多用途的催化反应,它为在医用化学和生物学中有用的复杂产品提供了一条快速合成路径,起始物为简单的、容易获取的烯烃。James Morken及同事开发出一种将单取代的末端烯烃通过“一锅化”对映选择性催化反应转化成若干手性产品的方法。这种“串联双硼化/交叉偶联反应”适用于一系列不同基质,只需要少量市售催化剂,并且能以高收率和高选择性提供产品。

Abstract 

Terminal, monosubstituted alkenes are ideal prospective starting materials for organic synthesis because they are manufactured on very large scales and can be functionalized via a broad range of chemical transformations. Alkenes also have the attractive feature of being stable in the presence of many acids, bases, oxidants and reductants. In spite of these attributes, relatively few catalytic enantioselective transformations have been developed that transform aliphatic α-olefins into chiral products with an enantiomeric excess greater then 90 per cent. With the exception of site-controlled isotactic polymerization of α-olefins, none of these catalytic enantioselective processes results in chain-extending carbon–carbon bond formation to the terminal carbon. Here we describe a strategy that directly addresses this gap in synthetic methodology, and present a single-flask, catalytic enantioselective conversion of terminal alkenes into a number of chiral products. These reactions are facilitated by a neighbouring functional group that accelerates palladium-catalysed cross-coupling of 1,2-bis(boronates) relative to non-functionalized alkyl boronate analogues. In tandem with enantioselective diboration, this reactivity feature transforms alkene starting materials into a diverse array of chiral products. We note that the tandem diboration/cross-coupling reaction generally provides products in high yield and high selectivity (>95:5 enantiomer ratio), uses low loadings (1–2 mol per cent) of commercially available catalysts and reagents, offers an expansive substrate scope, and can address a broad range of alcohol and amine synthesis targets, many of which cannot be easily addressed with current technology.

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