Benzannulation of Indoles to Carbazoles and Its Applications for Syntheses of Carbazole Alkaloids

A novel and efficient method for the benzannulation of indoles to carbazoles is reported. γ-Carbonyl tert-butylperoxide is applied as a new diene building block for the π-extension of simple indoles. The synthetic utility of this method is demonstrated by concise and selective total syntheses of naturally occurring carbazole alkaloids, olivacine, and asteropusazole A.