Ni0.5Zn0.5Fe2O4@HA-PRS nanoparticle: A recoverable green catalyst for the synthesis of tetrahydrobenzo[b]pyrans in water

A green, efficient and simple technique for the synthesize of tetrahydrobenzo[b]pyrans through one-pot three-component reaction of dimedone, aromatic aldehydes and malonitrile as active methylene compound using immobilization of Preyssler heteropoly acid on Ni0.5Zn0.5Fe2O4 magnetite nanoparticles (MNPs), coated with hydroxyapatite (HA) as a catalyst is described. Comparing with the previous studies on preparation of these compounds, the present methodology suggests some benefits which include high yields, short reaction times and green reaction conditions (room teperature in H2O). More importantly, the magnetic catalyst was isolated from the reaction mixture using a simple magnet and efficiently reused at least five runs without any loss of catalytic activity. Thus, the developed separable catalysts are potentially beneficial for the economic production of organic compounds.