HFIP-promoted catalyst-free cascade reactions for the synthesis of biologically relevant 3,3-di(indolyl)indolin-2-ones from indoles and isatins

Abstract

The first HFIP-promoted catalyst-free cascade reactions for the synthesis of biologically relevant 3,3-di(indolyl)indolin-2-ones (27 examples, up to 98% yield) from readily available indoles and isatin derivatives are described. This protocol shows well tolerance of different functional groups and features mild reaction conditions such as short reaction time (∼ 1 h), no usage of catalyst, easy operation and product isolation. Of particular interest is the formation of two CC bonds and one all-carbon quaternary center. This protocol could serve as an alternative strategy to synthesize biologically important 3,3-di(indolyl)indolin-2-ones for biological testing.