New electrophilic reactions of 2,2′-bisindolyls with acid chlorides and carbodienophiles

Some new acylation and cyclization reactions of 2,2′-bisindolyls 1, 2 are described. The product patterns constitute acyl derivatives 3, 4, 5 and an aldehyde 7 , indolo2,3-a]carbazoles 6, 14, 17, 19, 20 and cyclopentadiindoles 22 and 24 . In the reaction with aryne or diazotated anthranilic acid, a 3-benzoylindole derivative 9 and phenylindolyl azo dye 10 are formed. N-methylmaleimide reacts with 2,2′-bisindolyl 2 via Michael type addition, dehydrogenation and cyclization to several functionalized or anellated indole derivatives 11, 12, 13 and 14 , respectively.