Gold(I)-Catalyzed Pathway-Switchable Syntheses of Azocine[4,5-b]indole and (1H-indol-3-yl)-Azepino[4,5-b]indole Derivatives

A pathway-switchable gold(I)-catalyzed N-propargyl tryptamine cycloisomerization strategy was developed and successfully used for the syntheses of azocine[4,5-b]indole and (1H-indol-3-yl)-azepino[4,5-b]indole derivatives. The optimal reaction conditions for the two pathways were determined through detailed studies, and the scope of this pathway-switchable approach was explored using a series of N-propargyl tryptamine substrates. A gold(I)-catalyzed 8-endo-dig or 7-exo-dig cycloisomerization mechanism regulated by substituents and nucleophiles was proposed.