Interference of the Surface of the Solid on the Performance of Tethered Molecular Catalysts,Journal of the American Chemical Society

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Interference of the Surface of the Solid on the Performance of Tethered Molecular Catalysts
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2012-07-27 , DOI: 10.1021/ja304181q
Junghyun Hong ₁ , Francisco Zaera ₁

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The catalytic performance of cinchonidine in the promotion of thiol additions to conjugated ketones was used as a probe to assess the tethering of molecular functionality onto solid surfaces using well-known "click" chemistry involving easy-to-react linkers. It has been assumed in many applications that the tethered molecules retain their chemical properties and dominate the chemistry of the resulting solid systems, but it is shown here that this is not always the case. Indeed, a loss of enantioselectivity was observed upon tethering, which could be accounted for by a combination of at least three effects: (1) the nonselective catalytic activity of the surface of the solid itself; (2) the activity of the OH species generated by hydrolysis of some of the Si-alkoxy groups in the trialkoxy moieties used to bind many linkers to oxide surfaces; and (3) the bonding of the molecule to be tethered directly to the surface. Several ideas were also tested to minimize these problems, including the silylation of the active OH groups within the surface of the oxide support, the selection of solvents to optimize silane polymerization and minimize their breaking up via hydrolysis or alcoholysis reactions, and the linking at defined positions in the molecule to be tethered in order to minimize its ability to interact with the surface.

中文翻译：

固体表面对系留分子催化剂性能的干扰

辛可尼丁在促进硫醇加成到共轭酮中的催化性能被用作探针，使用涉及易于反应的接头的众所周知的“点击”化学来评估分子功能在固体表面上的束缚。在许多应用中，已经假设系留分子保留其化学性质并主导所得固体系统的化学性质，但这里表明情况并非总是如此。事实上，在束缚时观察到对映选择性的损失，这可以由至少三种效应的组合来解释：（1）固体本身表面的非选择性催化活性；(2) 三烷氧基部分中的一些 Si-烷氧基水解产生的 OH 物质的活性，用于将许多连接体结合到氧化物表面；(3) 待直接连接到表面的分子的键合。还测试了几种想法以尽量减少这些问题，包括氧化物载体表面内活性 OH 基团的硅烷化、选择溶剂以优化硅烷聚合并最大限度地减少它们通过水解或醇解反应的分解，以及在定义的连接分子中的位置被束缚，以尽量减少其与表面相互作用的能力。

更新日期：2012-07-27

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