A Polymeric Heterogeneous Catalyst Based on Polyacrylamide for Knoevenagel Reaction in Solvent Free and Aqueous Media.

Modified polyacrylamide containing amino functionality was synthesized by transamidation of polyacrylamide with 1,6-diamino hexane. The catalyst was easily characterized by routine analytical methods. It proved to be an efficient and chemoselcetive heterogeneous catalyst for Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate, malononitrile, and cyanoacetamide in water and solvent-free system to afford the desired alkenes in good purity and yields. Ketones were almost unreactive. The reactivity of the catalyst increased considerably in protic polar solvents such as water and ethanol. The order of reactivity of methylene compounds was malononitrife cyano ethylacetate cyanoacetamide. The results showed that the polymeric catalyst could be regenerated and used many times. The green and mild reaction condition, medium to short reaction time, high to excellent yields, low cost, readily preparation, and easy work up of the reactions are the main advantages of this catalyst.