Solid silica-based sulfonic acid: A remarkably efficient heterogeneous reusable catalyst for the one-pot synthesis of 2H-indazolo[2,1-b]phthalazine-triones

A novel, efficient and one-pot method for preparation of 2H-indazolo [2,1-b] phthalazine-trione derivatives is reported using solid silica-based sulfonic acid as an effective heterogeneous catalyst under thermal and solvent-free conditions. This method has the advantages of high yields, a cleaner reaction, simple methodology, easy work-up and greener conditions. The catalyst is easily prepared, stable (up to 300 C), reusable and efficient under the reaction conditions. Keywords: Dimedone, 2H-indazolo[2,1-b]phthalazine-trione, indazolophthalazine, solid silica-based sulfonic aci