Zhao Xiaorui, Cao Yueqiang, Duan Linlin, Yang Ruoou, Jiang Zheng, Tian Chao, Chen Shangjun, Duan Xuezhi, Chen De, Wan Ying
Key Laboratory of Resource Chemistry of Ministry of Education, Shanghai Key Laboratory of Rare Earth Functional Materials, Department of Chemistry, Shanghai Normal University, Shanghai 200234, China.
State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China.
Natl Sci Rev. 2020 Jun 11;8(4):nwaa126. doi: 10.1093/nsr/nwaa126. eCollection 2021 Apr.
The functionalization of otherwise unreactive C-H bonds adds a new dimension to synthetic chemistry, yielding useful molecules for a range of applications. Arylation has emerged as an increasingly viable strategy for functionalization of heteroarenes which constitute an important class of structural moieties for organic materials. However, direct bisarylation of heteroarenes to enable aryl-heteroaryl-aryl bond formation remains a formidable challenge, due to the strong coordination between heteroatom of N or S and transitional metals. Here we report Pd interstitial nanocatalysts supported on ordered mesoporous carbon as catalysts for a direct and highly efficient bisarylation method for five-membered heteroarenes that allows for green and mild reaction conditions. Notably, in the absence of any base, ligands and phase transfer agents, high activity (turn-over frequency, TOF, up to 107 h) and selectivity (>99%) for the 2,5-bisarylation of five-membered heteroarenes are achieved in water. A combination of characterization reveals that the remarkable catalytic reactivity here is attributable to the parallel adsorption of heteroarene over Pd clusters, which breaks the barrier to electron transfer in traditional homogenous catalysis and creates dual electrophilic sites for aryl radicals and adsorbate at C2 and C5 positions. The -band filling at Pd sites shows a linear relationship with activation entropy and catalytic activity. The ordered mesopores facilitate the absence of a mass transfer effect. These findings suggest alternative synthesis pathways for the design, synthesis and understanding of a large number of organic chemicals by ordered mesoporous carbon supported palladium catalysts.
对原本不活泼的碳氢键进行官能团化，为合成化学增添了新的维度，可生成适用于一系列应用的有用分子。芳基化已成为杂芳烃官能团化越来越可行的策略，杂芳烃是有机材料中一类重要的结构部分。然而，由于氮或硫的杂原子与过渡金属之间的强配位作用，杂芳烃的直接双芳基化以形成芳基-杂芳基-芳基键仍然是一个巨大的挑战。在此，我们报道了负载在有序介孔碳上的钯间隙纳米催化剂，作为五元杂芳烃直接高效双芳基化方法的催化剂，该方法允许绿色温和的反应条件。值得注意的是，在没有任何碱、配体和相转移剂的情况下，在水中实现了五元杂芳烃2,5-双芳基化的高活性（转换频率，TOF，高达107 h）和选择性（>99%）。一系列表征表明，此处显著的催化反应活性归因于杂芳烃在钯簇上的平行吸附，这打破了传统均相催化中电子转移的障碍，并在C2和C5位置为芳基自由基和吸附物创造了双亲电位点。钯位点的能带填充与活化熵和催化活性呈线性关系。有序介孔促进了传质效应的缺失。这些发现为通过有序介孔碳负载钯催化剂设计、合成和理解大量有机化学品提供了替代合成途径。
