Palladium‐Catalyzed Synthesis of 2‐Aminoindoles by a Heteroanulation Reaction

Chelates are the key: A conceptually novel indole ring forming reaction through heteroanulation is available through the palladium-catalyzed reaction of N-alkenylanilides with primary or secondary amines. The key feature is the formation of an unprecedented σ,π-chelated palladium species (see scheme); nitrogen nucleophiles can add to the activated alkyne unit of this species to form the indole skeleton. (X=I, Br; HNR2R3=prim. or sec. amine; Ts=tosyl.)