Novel Synthesis of Indoles via Palladium-Catalyzed Reductive N-Heterocyclization of o-Nitrostyrene Derivatives

Indole derivatives were readily prepared from the reductive N-heterocyclization of o-nitrostyrene derivatives in the presence of a catalytic amount of PdCl2(PPh3)2–SnCl2 under carbon monoxide pressure (20 kg/cm2) at 100 °C for 16 h. With o-nitrostilbene, 2-phenylindole was obtained in 75% yield.