Treatment of N,N-dimethyl 2-[2-(2-ethynylphenyl)ethynyl] anilines (1) with 10 mol % of palladium chloride and 2 equiv of cupric chloride in n refluxing THF gave benzo[a]carbazoles (2) in good yields. A mechanistic study showed that this reaction must proceed through formation of haloindole (3) followed by a palladium(II)-catalyzed atom transfer cyclization reaction to give the benzo[a]carbazoles.
