Reactions of 1,2-bis(1H-indol-2-yl)ethane:: Formation of indolo[2,3-c]carbazole and cyclohept[1,2-b:5,4-b′]bisindole derivatives

1,2-Bis(1H-indol-2-yl)ethane (9) has been prepared and converted into indolo[2,3-c]carbazole (8) using palladium acetate in refluxing acetic acid. Reaction of 9 with CoF3 in hot TFA led to isolation of cyclohept[1,2-b:5,4-b']bisindole derivatives 11 and 12, which could be elaborated into further derivatives. Treatment of 9 with orthoesters, aldehydes and ketones under acidic conditions afforded additional bisindoles containing a seven-membered ring. (C) 2000 Elsevier Science Ltd. All rights reserved.