Iodine-mediated cascade cyclization of enediynes to iodinated benzo[a]carbazoles.

Treatment of N,N-dimethyl 2-[2-(2-ethynylphenyl)ethynyl]anilines (1) with 1.2 equiv of iodine in CH2Cl2 gave benzo[a]carbazoles (2) in good yields. Mechanistic studies showed this reaction must go through the haloindole (3) followed by iodonium ion catalyzed atom-transfer cyclization reaction to give the benzo[a]carbazoles.