Recyclable Boron Sulfonic Acid as an Environmentally Benign Catalyst for the One-Pot Synthesis of Coumarin Derivatives under Solvent-Free Condition

A mild and green method has been developed for the preparation of coumarins derivatives through the one-pot reactions. In our study,various phenols and ethyl acetoacetate compound in which we used silica-supported boron sulfonic acid [SiO2/B(SO4H)3] as a new, highly efficient and tri-functional inorganic Brønsted acid catalyst were processed under solvent-free condition and thermal. The catalysts were separated easily from reaction mixture, regenerated after a simple activation step and reused at least six times without significant loss in catalytic activity. The most significant features of this procedure are:short period of conversion and excellent yields, simple experimental procedure, environmentally benign, the elimination of corrosive liquid acids and green aspects by avoiding toxic conventional catalysts and solvents.