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Surface ligands enhance the catalytic activity of supported Au nanoparticles for the aerobic α-oxidation of amines to amides

机译:表面配体增强了支持的Au纳米颗粒的催化活性,用于胺对酰胺的有氧α-氧化

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The catalytic aerobic α-oxidation of amines in water is an atom economic and green alternative to current methods of amide synthesis. The reaction uses O2 as terminal oxidant, avoids hazardous reactants and gives water as the only byproduct. Here we report that the catalytic activity of silica-supported Au nanoparticles for the aerobic α-oxidation of amines can be improved by tethering pyridyl ligands to the support. In contrast, immobilization of thiol groups on the material gives activities comparable to Au supported on bare silica. Our studies indicate that the ligands affect the electronic properties of the Au nanoparticles and thereby determine their ability to activate O2 and mediate C–H cleavage in the amine substrate. The reaction likely proceeds via an Au catalyzed β-hydride elimination enabled by backdonation from electron-rich metal to the orbital. O2, which is also activated on electron-rich Au, acts as a scavenger to remove H from the metal surface and regenerate the active sites. The mechanistic understanding of the catalytic conversion led to a new approach for forming C–C bonds α to the N atoms of amines.
机译:水中胺的催化有氧α-氧化是当前酰胺合成方法的原子经济和绿色替代品。该反应使用O2作为末端氧化剂,避免有害反应物,并将水作为唯一的副产品。在这里,我们报告说,可以通过将吡啶基配体绑定到载体来改善二氧化硅支持的Au纳米颗粒对有氧α氧化的催化活性。相反,硫醇基团在材料上的固定化提供了与裸二氧化硅支持的AU相当的活性。我们的研究表明,配体会影响Au纳米颗粒的电子特性,从而确定它们激活O2并介导胺基底中C – H裂解的能力。该反应可能是通过AU催化的β-氢化物消除来进行的,该反应通过从富含电子金属到轨道的逆转来实现。 O2也被激活在富含电子的AU上,是清除剂从金属表面去除H并再生活性位点的清道夫。对催化转化的机械理解导致了一种新的方法,该方法是形成与胺N原子的C – C键。

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