Silica-bonded S-sulfonic acid a recyclable catalyst for the synthesis of coumarins

Silica-bonded S-sulfonic acid (SBSSA) was prepared by the reaction of 3-mcrcaptopropylsilica (MPS) and chlorosulfonic acid in chloroform. This solid acid has been employed as a recyclable catalyst for the synthesis of coumarins from phenols and β-keto-esters at 80 ℃ under solvent-free conditions.