A silver-catalyzed TEMPO oxidative homo dimerization of indoles was first successful demonstrated. This new methodology is both atom and step efficient, allowing the synthesis of substituted C3–C3′ bisindolin-2-ones in moderate to excellent yields.

A simple, convenient and efficient metal-free catalyzed oxidative trimeric reaction of indoles toward a variety of 2-(1H-indol-3-yl)-2,3′-biindolin-3-one derivatives in moderate to excellent yields has been developed. This transformation proceeds via a tandem oxidative homocoupling reaction by using TEMPO in air as an environmentally benign oxidant. This methodology provides an alternative approach for the direct generation of all-carbon quaternary centers at the C3 position of indoles.

Mild conditions have been developed to achieve NBS-induced homodimerization of indole derivatives with excellent regioselectivity at 15 °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.

A method for combinative oxidative homo dimerization and cyanomethylation of free indole derivatives catalysed by TEMPO and Pd(OAc)₂ was demonstrated for the first time.