From indoles to 3,3′-biindolin-2-ones: copper-catalyzed oxidative homocoupling of indoles

Abstract

A copper-catalyzed intermolecular oxidative homocoupling of indoles has been developed for the direct construction of valuable C3–C3 biindolyl scaffolds. Using this protocol, 3,3′-bisindolin-2-ones are obtained in good yields and with excellent chemo- and regioselectivity. The methodology shows good functional group tolerance, allows the use of easily available inexpensive precursors, has simple operation, and can be performed under mild reaction conditions. From a retrosynthetic point of view, the strategic formation of a C–C bond via C(sp³-H)/C(sp²-H) dehydrogenative coupling may be useful in indole-derived pharmaceuticals and natural products. Upon screening HepG-2, SCG-7901, MDA-MB-468, MDA-MB-435 and Ishikawa cancer cell lines, compound 2s exhibited a good inhibitory effect against HepG-2 at 10.49 ± 0.41 μM in vitro antitumor activities. Further studies, involving apoptosis ratio detection and cell cycle analysis, were conducted on compound 2s.