Synthesis of Polycyclic 3,3′-Biindoles via AgOTf-Catalyzed Nucleophilic Addition and Cycloisomerization

A method for the rapid synthesis of polycyclic 3,3′-biindole derivatives has been developed through AgOTf-catalyzed nucleophilic addition and cycloisomerization processes. The cascade reaction employs readily accessible indoles and their N-2-formylphenyl derivatives and provides functionalized polycyclic 3,3′-biindoles in moderate to good yields under mild conditions. This reaction is highly efficient and takes only several minutes (∼5 min). Notably, the method is also highlighted by a Selectfluor-mediated oxidation reaction that quickly generates the oxindole derivatives.