Iron Ore Pellet, A Natural and Reusable Catalyst for Synthesis of Pyrano[2,3-d]pyrimidine and Dihydropyrano[c]chromene Derivatives in Aqueous Media

We wish to report a mild and efficient one-pot three-component reaction of an aryl aldehyde, malononitrile and barbituric acid or 4-hydroxycoumarinfor the synthesis ofpyrano[2,3-d]pyrimidine and dihydropyrano[c]chromene derivatives in the presence of iron ore pellet as a natural and reusable catalyst under heterogeneous and green conditions. The present methodology offers several advantages such as excellent yields, simple procedure and work up steps, short reaction times and easy recovery of the catalyst. We have also demonstrated that the catalyst can be reused successfully after six times using the same catalyst with high yields. Use of water as the reaction medium makes the process environmentally benign.