Kazuhiro Chiba, Tetsuya Hirano, Yoshikazu Kitano and Masahiro Tada
The intermolecular hetero-Diels–Alder reaction of in situ-generated o-quinomethanes and unactivated alkenes has been accomplished through a wet montmorillonite catalyst in a LiClO4–MeNO2 solution to give good yields of varied chromane skeletons.