Covalently anchored sulfonic acid onto silica as an efficient and recoverable interphase catalyst for the synthesis of 3,4-dihydropyrimidinones/thiones

A novel covalently anchored sulfonic acid onto the surface of silica was prepared and investigated for the Biginelli reaction. The catalyst is highly stable, completely heterogeneous and recyclable for several times. The work-up procedure is very simple and Biginelli compounds were obtained in good to excellent yields. (c) 2006 Elsevier B.V. All rights reserved.