First Total Synthesis of the Cytotoxic Carbazole Alkaloid Excavatine‐A and Regioselective Annulation to Pyrano[2,3‐<i>a</i>]carbazoles and [1,4]Oxazepino[2,3,4‐<i>jk</i>]carbazoles

Abstract

We describe the first total synthesis of the cytotoxic carbazole alkaloid excavatine‐A. The carbazole framework was constructed through double C–H bond activation of a diarylamine by using our palladium(II)‐catalyzed oxidative cyclization. Treatment of the intermediate 8‐hydroxycarbazoles with prenal and different additives led either to pyrano[2,3‐ a ]carbazoles or to [1,4]oxazepino[2,3,4‐ jk ]carbazoles. The pyran annulation was investigated to determine the influence of substitution pattern, additives, and reaction time on the selectivity.