A Brønsted acid catalyzed tandem Diels−Alder/aromatization reaction of 2-vinylindoles has been developed. The reaction provides a highly efficient and concise approach to 3-indolyl-substituted tetrahydrocarbazoles with various substituents in high yields under mild conditions.
While the presence of sulfur⋅⋅⋅πbonding interaction is a general phenomenon in the biological systems, the exploitation of this noncovalent force in a chemical process yet remains elusive. Herein, we describe the concept of chalcogen⋅⋅⋅πbonding catalysis that activates molecules of π systems through the interaction between chalcogen and π‐electron cloud. The proof‐of‐concept studies using a vinylindole‐based