Low-temperature synthesis of pyrano- and furo[3,2-c]quinolines via Povarov reaction using a highly ordered 3D nanoporous catalyst with a high acidity

The imines generated in situ from aryl amines and cyclic enol ethers undergo smooth [4+2] cycloaddition with 3,4-dihydro-2H-pyran (DHP) and 2,3-dihydrofuran (DHF) using the Bronsted acid sites on the aluminosilicate wall structure of the nanoporous catalyst under mild reaction conditions to afford the corresponding pyrano- and furo[3,2-c]quinolines, respectively, in good yields with high diastereoselectivity. The high activity of the catalyst is due to its high surface area, large pore volume, and well-ordered porous structure with high acidity. In addition, the catalyst was found to be highly stable and can be reused several times without affecting the activity of the catalyst.