Copper-catalyzed cascade double C3-indolations of 3-diazoindolin-2-imines with indoles: convenient access to 3,3-diaryl-2-iminoindoles.

Symmetrical 3,3-diaryl-2-iminoindoles were prepared from 3-diazoindolin-2-imines and indoles via a copper-catalyzed cascade arylation/dehydrogenative cross-coupling process. By controlling the molar ratio of reactants and the operation procedure, 3-aryl-2-aminoindoles and asymmetrical 3,3-diaryl-2-iminoindoles could be approached.