Synthesis of Benzopyrano[۲,۳-d]pyrimidines Using Silica-Bonded N-Propyldiethylenetriamine Sulfamic Acid (SPDTSA) As Heterogeneous Solid Acid Catalyst under Solvent-Free Conditions

Silica-bonded N-propyldiethylenetriamine sulfamic acid (SPDTSA) is employed as a recyclable heterogeneous solid acid catalyst for the synthesis of benzopyrano[۲,۳-d]pyrimidines  through one-pot condensation reaction of salicylaldehydes, malononitrile and secondary amines  at room temperature under solvent-free conditions. SPDTSA showed much the same efficiency when used in consecutive reaction runs.