TiO2-SO42−: A recyclable heterogeneous catalyst for the microwave-mediated synthesis of benzylamino coumarin derivatives in water

Abstract A new and environmentally benign protocol was developed for the synthesis of a series of benzylamino coumarin derivatives via the multicomponent reactions of 4-hydroxycoumarin, aromatic aldehyde and cyclic secondary amine in water using sulfated titania (TiO2-SO42−) as a heterogeneous solid acid catalyst under microwave irradiation at 100°C. The proposed method is advantageous due to its simple reaction procedure, high yield, easy work-up, short reaction time, and reusability of sulfated titania (TiO2-SO42−) and its high adaptability for the synthesis of benzylamino coumarin derivatives in good to excellent yields. The catalyst can be easily recovered and reused with almost the same catalytic activity. The structure of the benzylamino coumarin derivatives was confirmed by melting points, elemental analysis, IR, 1H, and 13C NMR and 2D NMR spectral data. Higher catalytic activity of sulfated titania (TiO2-SO42−) is due to its increased Bronsted acidity.