A Novel and Efficient Catalyst to One-Pot Synthesis of 2-Amino-4H-chromenes by p-Toluenesulfonic Acid

The synthesis of 2-amino-4H-chromenes through a three-component reaction employing p-toluenesulfonic acid as catalyst was performed. A mixture of an appropriate benzaldehyde, malononitrile, α- or β-naphthol and p-toluenesulfonic acid, in acetonitrile was refluxed for 3 h. After completion of the reaction which was monitored by TLC, the mixture was cooled to room temperature and filterated. The filtrate was washed twice with 5% NaHCO 3 and dried over MgSO4. The solvent was evaporated under reduced pressure and the crude product was obtained. Melting points were measured by using the capillary tube method with an electro thermal 9200 apparatus. The effect of the nature of the substituents on the aromatic ring showed no apparent effect on this conversion because they were obtained in high yields in relatively short reaction times.