Direct Access to Bridged Tetrahydroquinolines and Chromanes via an InCl3‑Catalyzed Sequential Three-Component Cascade

A sequential three-component cascade process was developed for the synthesis of bridged tetrahydroquinolines and chromanes bearing 2,6-methanobenzo­[d]­[1,3]­diazocine and 2,6-methanobenzo­[g]­[1,3]­oxazocine scaffolds, respectively, in good yields from readily available materials. The InCl3-catalyzed reaction progressed via enamine formation, Michael addition, intramolecular cyclization, and intramolecular iminium ion cyclization steps. Notably, this high atom economic approach (−2H2O) allowed the generation of four new bonds (1 C–C and 3 C–N or 1 C–C, 1 C–O and 2 C–N) and two heterocyclic rings in a single operation.