Acid-Catalyzed Cascade Ring-Opening and Addition Reactions of Arylvinylcyclopropenes with α,β-Unsaturated Substrates, Scope and Limitations

Catalyzed by Al(III) catalyst, arylvinylcyclopropenes react with α,β-unsaturated substrates smoothly to produce the Diels−Alder adducts in moderate to good yields through a cascade ring-opening reaction/Diels−Alder cycloaddition. On the other hand, strong Brønsted acid TfOH can promote the cascade intramolecular Friedel−Crafts/1,4-addition reaction to produce indene derivatives in moderate to good yields under mild conditions. The acidity of the catalysts plays a key role in these reactions.