Polymeric nanoassembly of imine functionalized magnetite for loading copper salts to catalyze Henry and A3-coupling reactions

Abstract

Poly(ethylenimine) was grafted on the magnetite (Fe3O4) nanoparticles, and subsequently reacted with different aldehydes to form the imine functionalities (Fe3O4-Imine NPs). Thus formed Fe3O4-Imine NPs could host copper salts generally used as the homogeneous catalyst in organic reactions with the stability prerequisite for the recycling. The expected chemical structures of Fe3O4-Imine NPs were ascertained by the FTIR and CHNS analyses. The physical structure of Fe3O4-Imine NPs was found to be corn-like assemblies from the images obtained by FESEM and HRTEM. The Fe3O4-Imine NPs assemblies possessed the superparamagnetic properties which made possible to withdraw these particles from the reaction solution efficiently. The copper salt loading capacity of the Fe3O4-Imine was lower than that of the Fe3O4-PEI, but the water content in the Fe3O4-Imine was higher (10 wt%) than that of the Fe3O4-PEI (2.5 wt%). Among different aldehydes and copper salts used, the Fe3O4-Imine formed by benzaldehyde and loaded with copper acetate salt exhibited better catalytic activity in the Henry reactions using water as the solvent. Also, the Fe3O4-Imine showed better catalytic activity than that obtained using the Fe3O4-PEI in both Henry reactions and A3-coupling of aldehyde, pyrrolidine, and phenyl acetylene reactants. The several representative examples of these coupling reactions were studied to understand the different parameters affecting the catalytic efficacy of copper acetate loaded Fe3O4-Imine.