1,4-Dipolar Cycloaddition Reactions in Ionic Liquids: A Facile Synthesis of 9aH,15H-[1]Benzopyrano[3′,2′: 3,4]pyrido[2,1-a]isoquinolines (=9aH,15H-Benzo[a][1]benzopyrano[2,3-h]quinolizines)

Ionic liquids were found to be a suitable reaction medium for 1,4-dipolar cycloaddition reactions of an isoquinoline, an activated alkyne, and a 4-oxo-4H-1-benzopyran-3-carboxaldehyde at room temperature to afford [1]benzopyrano-pyrido-isoquinoline (=9aH,15H-benzo[a][1]benzopyrano[2,3-h]quinolizine) derivatives selectively in good yields. The ionic liquid can be recovered and recycled in further runs without loss of activity.