Magnetic iron oxide/phenylsulfonic acid: A novel, efficient and recoverable nanocatalyst for green synthesis of tetrahydrobenzo[b]pyrans under ultrasonic conditions

A novel magnetic iron oxide supported phenylsulfonic acid (Fe₃O₄@Ph-SO₃H) with core-shell structure is prepared, characterized and applied as efficient nanocatalyst for green synthesis of tetrahydrobenzo[b]pyrans. The Fe₃O₄@Ph-SO₃H was prepared via modification of magnetic iron oxide cores with 1,4-bis(triethoxysilyl)benzene (BTEB) followed by sulfonation of aromatic rings. The Fe₃O₄@Ph-SO₃H was characterized using FTIR, TGA, PXRD, SEM, TEM, VSM and EDX techniques. This was effectively applied for synthesis of tetrahydrobenzo[b]pyrans in water as green solvent at room temperature under ultrasonic conditions. The products were obtained in high to excellent yields at short times. The recoverability, reusability and durability of this nanocatalyst were studied under applied reaction conditions.