磁性纳米粒子Fe_3O_4@PEI@Ru(OH)_x催化的分子氧氧化醇-克脑文格尔串联反应

One-pot Tandem Aerobic Oxidation/Knoevenagel Condensation Reaction Catalyzed by Magnetic Nanoparticles Fe_3O_4@PEI@Ru( OH)_x

以聚乙烯亚胺改性的四氧化三铁纳米粒子为载体负载Ru(OH)_x得到负载钌催化剂Fe_3O_4@PEI@Ru(OH)_x.该催化剂在分子氧氧化醇-克脑文格尔缩合"一锅"串联反应中显示优良的催化性能,多种结构的醇被选择性地氧化为相应的醛进而与活性亚甲基化合物缩合生成相应的缩合产物.采用外磁铁可以很容易地将催化剂与反应混合物分离,实现催化剂的回收.然而,该催化剂的循环使用性能较差.电感耦合等离子体原子发射光谱(ICP-OES)分析证明催化剂在反应过程中没有发生钌的流失.X射线光电子能谱(XPS)分析发现催化剂失活是由于反应过程中活性的Ru^(3+)被部分地氧化为非活性的Ru^(4+)所致.

A supported ruthenium catalyst Fe3 O4@ PEI@ Ru（ OH）xwas obtained by immobilization of Ru（ OH）x onto polyethyleneimine-modified magnetic nanoparticles. The catalyst showed good performance in the one-pot tandem aerobic oxidation-Knoevenagel condensation of alcohols and active methylene compounds. This catalyst can be readily separated from reaction mixture and recovered by an external magnet. However,this catalyst exhibited poor recyclability. Analysis results of X-ray photoelectron spectroscopy（ XPS） confirmed that no ruthenium leaching occurred during the catalytic run. The analysis result of inductively coupled plasma atomic emission spectrometry（ ICP-OES） revealed that the deactivation of the catalyst was due to the partial oxidation of active Ru^（3＋）to inert Ru^（4＋）in the reaction.