An Efficient and Recyclable Mesostructured Polymer-Supported N-Heterocyclic Carbene-Palladium Catalyst for Sonogashira Reactions

Abstract

Palladium catalyst systems are the most widely used for the formation of C-C and C-N bonds. Environmentally friendly heterogeneous palladium catalysts have strongly stimulated growth in this research area. Herein, a FDU (Fudan University)-15 mesopolymer with p6mm mesostructures that combine the advantages of organic polymers and mesoporous materials was investigated as a new solid support for Pd complexes. The FDU-15 mesopolymer-supported N -heterocyclic carbene (NHC) precursor was developed by a simple chemical functionalization approach. It has been used as a phosphine-free ligand to prepare the novel heterogeneous palladium catalyst FDU-NHC/Pd(II), which efficiently catalyzes Sonogashira reactions between aryl halides and terminal alkynes to afford the corresponding products in good yields. Various techniques such as X-ray diffraction, N 2 adsorption-desorption isotherms, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy have been used to characterize the catalyst. The results indicate that the mesoporous structure of FDU-15 was not affected by immobilization, however, the pore diameter, pore volume, and BET surface area decrease. The stability of the heterogeneous catalyst was also studied. The FDU-NHC/Pd(II) complex catalyst was easily separated from the reaction system by a simple filtration of the reaction mixture and it has been shown to be robust without a significant loss of catalytic activity after recycling and reuse in 10 times. 新型有机介孔材料 FDU-15 负载卡宾配体络合醋酸钯催化剂 FDU-NHC/Pd(II) 的制备方法简单, 通过三步反应即可制得, 采用 X 射线衍射、N 2 吸附-脱附和透射电镜等手段对催化剂进行了表征, 并考察了它在 Sonogashira 偶联反应中的催化性能. 结果表明, 功能化不影响 FDU-15 的有序介孔结构, 仅其孔径、孔体积和 BET 比表面积有所减小. 另外, 该催化剂在 Sonogashira 偶联反应中表现出较高的催化活性, 底物普适性好, 无论是带有吸电子取代基还是供电子取代基的碘苯都能够得到较高的分离产率, 且该催化剂分离简单, 重复使用 10 次以上时, 其催化性能基本保持不变. A novel heterogeneous palladium catalyst FDU-NHC/Pd(II) was developed. It is highly active in Sonogashira reactions between aryl halides and terminal alkynes. The catalyst can be recycled and reused ten times without significant loss of activity.