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.