Superparamagnetic Nanoparticle-Supported Imidazole as an Efficient and Magnetically Recyclable Organocatalyst for Konevenagel Condensation

Superparamagnetic nanoparticle-supported imidazole (Im@MNPs) was prepared and used as magnetically separable catalyst for Knoevenagel condensation of aromatic aldehydes with active methylene compounds. 3.0 mol% of Im@MNPs with water as solvent was investigated as the optimal catalytic system. The active methylene compounds involved malononitrile, ethyl 2-cyanoacetate, 2-(1H-benzo[d]imidazol-2-yl)acetonitrile, 2- (benzo[d]thiazol-2-yl)acetonitrile, 2-phenylacetonitrile, 2-(3-chlorophenyl)acetonitrile, 2-(1H-indol-3- yl)acetonitrile. All reactions preceded smoothly affording target products in good to excellent yields (78-99%) within minutes to hours. More importantly, the catalyst could be reused up to ten times with only a slight decrease in catalytic activity. A plausible mechanism was proposed to rationalize the high catalytic activity of catalyst.