AlCl_(3)@MNPs催化硫杂Michael加成串联反应研究

Research on Thia-Michael Addition Tandem Reactions Catalyzed by AlCl_(3)@MNPs

利用化学共沉淀法制备了超顺磁性Fe_(3)O_(4)纳米颗粒,然后在碱性环境中水解正硅酸四乙酯得到二氧化硅包覆的核壳结构(MNPs),进一步负载Al Cl_(3)得到非均相催化剂Al Cl_(3)@MNPs.采用X射线电子能谱、X射线衍射、透射电镜、扫描电镜及磁滞回线测试等手段对Al Cl_(3)@MNPs的物化性能和结构进行表征,表明氯化铝通过与载体表面弱配位键的形成成功负载到磁性纳米粒上.将得到的超顺磁性纳米粒负载的氯化铝(AlCl_(3)@MNPs)应用到硫杂Michael加成串联反应中.研究发现,该催化剂能有效促进胺、二硫化碳和α,β-不饱和羰基化合物加成反应,产品收率为59%~99%.催化剂具备的超顺磁性纳米颗粒的大表面积、反应时的良好分散性和Al Cl_(3)与载体表面羟基的配位作用保证了其高催化活性.另外,由于Al Cl_(3)@MNPs的超顺磁性,在外加磁场存在条件下可以简便回收,并重复使用10次,其催化效果未见大幅下降,明显优于未负载Al Cl_(3)母体,这显示了其良好的工业化应用前景.

Magnetic nanoparticles(MNPs),prepared by co-precipitation method,were coated using hydrolysis of tetraethyl orthosilicate(TEOS)under basic conditions.The core-shell structured supporters were further grafted by AlCl_(3)to obtain the finally catalyst AlCl_(3)@MNPs,which was fully characterized by X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),transmission electron microscopy(TEM),scanning electron microscope(SEM)and vibrating sample magnetometer(VSM),indicating the successful immobilization of AlCl_(3)on the surface of the MNPs through coordination bond,and the magnetic nanoparticles supported aluminum chloride AlCl_(3)@MNPs was used in the thia-Michael addition tandem reactions.The as-prepared catalyst AlCl_(3)@MNPs promoted smoothly the reaction of amines,carbon disulfide andα,β-unsaturated carbonyl compounds to achieve good to excellent product yields of 59%~99%.Large surface area,excellent dispersion of catalyst in reaction solution and coordinative bond between AlCl_(3)and hydroxyl cluster in MNPs ensure the highly catalytic efficiency.In addition,AlCl_(3)@MNPs can be readily recovered with external magnetic field and recycled for 10 times without significant loss of catalytic activity,demonstrating its advantage over the precursor AlCl_(3)and excellent potential in industrial application.