Amine functionalized SiO2@Fe3O4 as a green and reusable magnetic nanoparticles system for the synthesis of Knoevenagel condensation in water

Amine functionalized SiO2@Fe3O4 as an efficient, green, and recyclable catalyst was synthesized using a simple approach. Then, the catalytic activity of the amine-functionalized SiO2@Fe3O4 was evaluated in the metal-free green synthesis of Knoevenagel condensation from the various aromatic aldehydes and malononitrile in water to gives the corresponding 2-(aryl) methylenemalononitrile derivatives in excellent yields with a relatively low catalyst loading. Short reaction times, commercial availability of the starting materials, being environmentally friendly, reusability of catalyst, high yields, low cost, and easy work-up are the attractive features of the present work. The reusability of the catalyst was investigated for the product 3a. After separation with an external magnet, the recycled catalyst can be reused in 7 consecutive runs. The yield of the product reduced from 97 to 91% over 7 times.