Asymmetric Catalysis at the Mesoscale: Gold Nanoclusters Embedded in Chiral Self-Assembled Monolayer as Heterogeneous Catalyst for Asymmetric Reactions,Journal of the American Chemical Society

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Asymmetric Catalysis at the Mesoscale: Gold Nanoclusters Embedded in Chiral Self-Assembled Monolayer as Heterogeneous Catalyst for Asymmetric Reactions
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2013-03-01 , DOI: 10.1021/ja310640b
Elad Gross _{1,

2} , Jack H. Liu _{1,

2} , Selim Alayoglu _{1,

2} , Matthew A. Marcus ₃ , Sirine C. Fakra ₃ , F. Dean Toste ₁ , Gabor A. Somorjai _{1,

2}

Affiliation

Research to develop highly versatile, chiral, heterogeneous catalysts for asymmetric organic transformations, without quenching the catalytic reactivity, has met with limited success. While chiral supramolecular structures, connected by weak bonds, are highly active for homogeneous asymmetric catalysis, their application in heterogeneous catalysis is rare. In this work, asymmetric catalyst was prepared by encapsulating metallic nanoclusters in chiral self-assembled monolayer (SAM), immobilized on mesoporous SiO2 support. Using olefin cyclopropanation as an example, it was demonstrated that by controlling the SAM properties, asymmetric reactions can be catalyzed by Au clusters embedded in chiral SAM. Up to 50% enantioselectivity with high diastereoselectivity were obtained while employing Au nanoclusters coated with SAM peptides as heterogeneous catalyst for the formation of cyclopropane-containing products. Spectroscopic measurements correlated the improved enantioselectivity with the formation of a hydrogen-bonding network in the chiral SAM. These results demonstrate the synergetic effect of the catalytically active metallic sites and the surrounding chiral SAM for the formation of a mesoscale enantioselective catalyst.

中文翻译：

中尺度不对称催化：嵌入手性自组装单层的金纳米团簇作为非对称反应的多相催化剂

为不对称有机转化开发高度通用的、手性的、多相催化剂的研究，在不淬灭催化反应性的情况下，取得了有限的成功。虽然通过弱键连接的手性超分子结构对于均相不对称催化具有很高的活性，但它们在非均相催化中的应用很少。在这项工作中，通过将金属纳米团簇包裹在手性自组装单层 (SAM) 中，并固定在介孔 SiO2 载体上来制备不对称催化剂。以烯烃环丙烷化为例，证明了通过控制 SAM 性质，嵌入手性 SAM 中的 Au 簇可以催化不对称反应。当使用涂有 SAM 肽的金纳米团簇作为形成含环丙烷产物的多相催化剂时，获得了高达 50% 的对映选择性和高非对映选择性。光谱测量将提高的对映选择性与手性 SAM 中氢键网络的形成相关联。这些结果证明了催化活性金属位点和周围手性 SAM 对形成中尺度对映选择性催化剂的协同作用。

更新日期：2013-03-01

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