Molecular Iodine-Catalyzed Imino-Diels-Alder Reactions: Efficient One-Pot Synthesis of Pyrano[3,2-c]quinolines

The successful use of molecular iodine as a catalyst in the intermolecular imino-Diels-Alder reaction is described. A one-pot synthesis of pyrano[3,2c]quinolines was achieved by three-component coupling of aldehydes and anilines with 2,3-dihydropyran catalyzed by iodine. The reactions could be carried out smoothly at room temperature within three to six hours to offer the target products in good yields. We also investigated solvent effect, sub stituent effect, and the amount of iodine required.