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

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 intere st is the formation of two C-C 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.