Synthesis of Bis-4-hydroxycoumarins via a Multi Component Reaction Using Silica Boron-sulfuric Acid Nanoparticles (SBSANs) as an Efficient Heterogeneous Solid Acid Catalyst

The silica boron sulfuric acid nanoparticles (SBSANs) as an efficient heterogeneous solid acid catalyst with both Brønsted and Lewis acidic sites catalyzed the preparation of bis-4-hydroxycoumarin derivatives using reaction of aldehydes and 4-hydroxycoumarin under mild and solvent-free condition at room temperature. This new and efficient methodology has advantages in comparison with currently used methods such as: easy work-up, simple separation of catalyst from the reaction mixture, reusability and lower catalyst loading, relatively short reaction time, eco-friendly with environment, excellent yields, simple purification of products and mild reaction condition. Using this method a range of biologically active bis-4-hydroxycoumarin derivatives were synthesized in good to excellent yield. The catalyst system was reusable at least for 5 times in this reaction without significant decreasing in its catalytic activity.