One-pot synthesis of pyrano[3,2-c]pyran derivatives catalyzed by KF/Al2O3

A series of pyrano[3,2-c] pyran derivatives have been synthesized by the reaction of aromatic aldehyde, malononitrile or cyanoacetate and 4-hydroxy-5-methylpyran-2-one in EtOH at room temperature catalyzed by KF/Al2O3. The structures of the products were characterized by IR, H-1 NMR and elemental analysis, and 4a was further confirmed by X-ray diffraction analysis.