Cycloaddition of Styrene Derivatives with Quinone Catalyzed by Ferric Ion: Remarkable Acceleration in an Ionic Liquid Solvent System.

Ferric ion-catalyzed cycloaddition of styrene derivatives with quinone gave 2,3-dihydrobenzofuran derivatives in excellent yields with trans selectivity; remarkable acceleration was observed when the reaction was carried out in an ionic liquid solvent system.