Access to Polycyclic Carbazoles from Ring-Fused 2-(9H-carbazol-1-yl)anilines

Nine 2-(9H-carbazol-1-yl)anilines with rings fused at the 3,4-position were acylated at the amino group with chloroacetyl, 3-chloropropanoyl, or 4-chlorobutyryl chloride, at yields of 85-99%. The resulting omega-chloroamides were exposed to potassium tert-butoxide in THF. All nine acetamides annulated exclusively at the carbazole N atom, giving benzodiazocinocarbazoles at 76-91% overall yield. The only propanamide prepared underwent alpha,beta-elimination, giving the corresponding acrylamide at 70% overall yield. All nine butanamides annulated exclusively at the amide nitrogen, giving pyrrolidin-2-ones at 70-94% overall yield. Additionally, the 1-indanone derived carbazolylaniline followed the same annulation pattern, but the benzylic methylene group was oxidized, giving the corresponding fluorenones. The cyclohexanone-derived carbazolylaniline was also converted into a maleimide, which participated in a Diels-Alder reaction with cyclopentadiene. Attempts to replace the amino group in the starting material via diazotization were unsuccessful. Instead, a Widman-Stoermer reaction was observed, in which the diazonium group attacked the carbazole 2-position, giving the corresponding cinnoline.