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.)