Selective Syntheses of Benzo[b]carbazoles and C3-Substituted Indoles via Tunable Catalytic Annulations of β-Alkynyl Ketones with Indoles

Tunable catalytic annulation reactions of beta alkynyl ketones with indoles have been developed, enabling multiple chemical bond-forming events to selectively access skeletally diverse indole-containing heterocycles with generally good yields. Silver-catalyzed intermolecular benzannulation reaction of beta-alkynyl ketones with indoles afforded tetracyclic benzo[b]carbazoles whereas isochromen-1-yl-substituted indoles could be obtained using the same silver catalysis by lowering the reaction temperature (0 degrees C or rt). Interestingly, using Sc(OTf)(3)and AgOTf as a combined catalytic system led to the formation of C3-naphthylated indolesviaintramolecular benzannulation reaction.