Action of 1,2‐diamines and o ‐aminophenols on 1‐alkyl‐3‐carboxyindole‐2‐acetic acid anhydrides. Preparation of new ring systems

1‐Alkyl‐3‐carboxyindole‐2‐acetic acid anhydrides (I) react with ethylenediamine and with o ‐phenylenediamine to give directly 10‐alkylimidazo[3,2:1′,2′]pyrido[4,5‐ b ]indol‐5(1 H )‐ones (II) and 5,6‐dihydro‐5‐alkyl‐13 H ‐indolo[2′,3′:4,5]pyrido[1,2‐ a ]benzimidazol‐13‐one (V), respectively. However, anhydrides I react with o ‐aminophenol and with o ‐aminothiophenol to give carboxyindole‐acetanilide derivatives IX, which can be cyclised to indolo[2′,3′:4,5]pyrido[2,1‐ b ]benzoxazolone and indolo[2′,3′:4,5]pyrido[2,1‐ b ]benzthiazolone (XI). Some derivatives of II and V were prepared to help in elucidating the structures.