Palladium-catalysed decarboxylative nitrile insertion via C-H activation or self-coupling of indole-2-carboxylic acids: a new route to indolocarbolines and triindoles.

Palladium catalysed-reaction of indole carboxylic acids with nitriles in the presence of Ag2CO3 proceeds via decarboxylative dual C-H activation leading to the nitrile insertion products, triazaindeno-fluorenes (indolocarbolines); in the absence of nitrile, diindolocarbazoles (heptacyclic triindoles or triazatruxenes) are formed.