A green method for the synthesis of indeno[1,2-b]pyridines using Fe3O4@SiO2@PrSO3H as a nanomagnetic catalyst

The acidic agent (SO3H) was stabilized on the silica coated Fe3O4 magnetic nanoparticles to produce Fe3O4@SiO2@PrSO3H, as a heterogeneous acidic catalyst, was designed, and then fully studied and characterized by FTIR, XRD, TGA, DTA, TEM, and SEM analysis. Subsequently, the catalytic activity of Fe3O4@SiO2@PrSO3H was investigated by the onepot four component condensation reaction between 1,3indandione, aromatic aldehydes, acetophenone or propiophenone and ammonium acetate under the solventfree condition at 80 ℃. The main advantages of this magnetic and heterogeneous acidic catalyst are high product yields, being environmentally benign, short reaction times, and easily separated from the reaction mixture using an external magnet.