Regioselective synthesis of 2,3′-biindoles mediated by an NBS-induced homo-coupling of indoles

Mild conditions have been developed to achieve NBS-induced homodimerization of indole derivatives with excellent regioselectivity at 15 degrees C in high efficiency. This method provides a simple route to a 2,3'-linked biindolyl scaffold from the electron-rich to moderately electron-poor indoles. In addition, [3,2-a] carbazole derivatives can also be prepared through this method.