Green method for the synthesis of indeno[1,2-b]pyridines using Fe3O4@SiO2@Pr-SO3H as nanomagnetic catalyst

The acidic agent (SO₃H) was stabilized on the silica coated Fe₃O₄ magnetic nanoparticles to produce Fe₃O₄@SiO₂@Pr-SO₃H, as a heterogeneous acidic catalyst, was designed, and then fully studied and characterized by FT-IR, XRD, TGA, DTA, TEM, and SEM analysis. Subsequently, the catalytic activity of Fe₃O₄@SiO₂@PrSO₃H was investigated by the one-pot
four- component condensation reaction between 1,3-indandione, aromatic aldehydes, acetophenone or propiophenone and ammonium acetate under the solvent-free 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.