Selective Synthesis of 2-Indolyl-3-oxoindolines or 2-(2-Aminophenyl)quinolines through Cu(II)- or Bi(III)-Catalyzed Tunable Dimerizations of 2-Alkynylanilines

A novel and selective synthesis of 2-indolyl-3-oxoindolines or 2-(2-aminophenyl)quinolines through tunable dimerizations of 2-alkynylanilines is presented. Mechanistically, the formation of 2-indolyl-3-oxoindolines involves a Cu(OAc)₂/O₂-promoted intramolecular cyclization of 2-alkynylaniline to give the required indole and 3H-indol-3-one intermediates followed by the indolylation of 3H-indol-3-one. On the other hand, the formation of 2-(2-aminophenyl)quinolines is believed to go through a Bi(OTf)₃/MesCO₂H-catalyzed intermolecular N-nucleophilic addition between two 2-alkynylaniline molecules to give an enamine intermediate followed by its intramolecular C-nucleophilic addition/annulation. Notable features of these new methods include easily obtainable substrates, economical catalysts and oxidant, controllable selectivity, and high versatility toward diverse products.