BiCl3-Mediated Tandem Cyclization of Tryptamine-Derived Ynamide: Concise Synthesis of Pentacyclic Spiroindolines and Tricyclic Indole Derivatives

Catalytic tandem cyclization of ynamides has attracted considerable interest in organic synthesis because of its atom economy in the rapid formation of polycyclic compounds. However, examples on the construction of pentacyclic spiroindolines are quite scarce. Herein, we described a BiCl3-mediated tandem cyclization reaction of tryptamine-ynamides, which led to the formation of appealing pentacyclic spiroindoline scaffolds in moderate to excellent yields. In addition, such a reaction can lead to the divergent synthesis of tricyclic indole derivatives with moderate yields by engineering substrate structures. The synthetic utility of this methodology has also been demonstrated by further interesting transformations.

Automated summary

This study presented a BiCl3-mediated tandem cyclization reaction of tryptamine-ynamides, leading to the formation of pentacyclic spiroindoline scaffolds in moderate to excellent yields. The reaction also demonstrated the divergent synthesis of tricyclic indole derivatives with moderate yields by manipulating substrate structures, showcasing the synthetic utility of the methodology.