Scandium perfluoroalkanesulfonate-catalyzed Diels–Alder reactions in an organic solvent

Scandium perfluoroalkanesulfonate-catalyzed Diels–Alder reactions proceeded smoothly in dry dichloromethane in the presence of molecular sieves (MS) 5 Å. It was found that water interfered with the reactions, contrary to most rare earth-catalyzed reactions that proceed smoothly in aqueous media. Among scandium perfluoroalkanesulfonates tested, scandium triflate (Sc(OTf)3), scandium pentafluoroethanesulfonate (Sc(OSO2C2F5)3), and scandium nonafluorobutanesulfonate (Sc(OSO2C4F9)3) gave the highest yields and selectivities.