Silica supported boric tri-sulfuric anhydride as a novel and efficient catalyst for solvent-free synthesis of coumarins via Pechmann condensation

It is found that silica supported boric trisulfuric anhydride (BTSA. SiO2) is a novel, suitable and versatile catalyst for efficient and clean synthesis of coumarins via Pechmann cyclocondensation under mild and solvent-free conditions. Different kinds of phenols and beta-ketoesters were subjected to the cyclization reaction. Particularly, this catalyst makes the condensation of less activated phenols feasible. Besides the described benefits, the reported catalyst was applied successfully for the synthesis of novel coumarins from 3-acetyldihydrofuran-2(3H)-one as well as estradiol (sex hormone).