The efficient and green syntheses of Pyrano [3,2-c] pyridine and Pyrano [4,3-6]pyran derivatives under microwave irradiation

A series of pyrano[3,2-c]pyridone and pyrano[4,3-b] pyran derivatives were synthesized efficiently by three-component reaction of aldehydes, 4-hydroxy-pyridin-2-(1H)-one or 4-hydroxy-2- pyranone and malononitrile in [bmim] BF ₄ under microwave irradiation without any catalyst. The reactions were rapid, enhanced efficiency, and environmentally benign, and the starting materials of the reactions were readily available. In addition, the procedure was successfully applied to the preparation of pyrimidine nucleoside hybrids of pyrano[3,2-c] pyridone or pyrano[4,3-b]-pyran.