Imino Diels-Alder reactions: Efficient synthesis of pyrano and furoquinolines catalyzed by ZrCl4

Anhydrous zirconium tetrachloride is found to be an efficient catalyst for the Imino Diels-Alder reactions of N-benzylideneanilines with 3,4-dihydro-2H-pyran and 2,3-dihydrofuran to afford pyrano and furo [3,2-c] quinolines in good yields.