Diels–Alder Reactions of 2-Vinylindoles with Cyclic Dienophiles: Synthesis of [c]-Annulated Tetrahydrocarbazoles

Diels–Alder reactions of 2-vinylindoles with cyclic carbo- and heterodienophiles, in the presence of suitable Lewis acids, led to uncommon [c]-carbo- and furoannulated tetrahydrocarbazoles. The obtained compounds encompass a carbonyl group in an angular position, suitable for further transformations, and represent useful intermediates for the synthesis of more complex structures.