One-pot Synthesis of 2-Aminoindole through SET Oxidative Cyclization: Concise Synthesis of Tryptanthrin and Phaitanthrin E

An efficient domino approach for the synthesis of biologically important 2-aminoindole derivatives has been developed using CuBr2-mediated SET oxidative cyclization as a key step. This one-pot multicomponent strategy utilizes readily available ethyl propiolate, tosyl azide, and substituted aryl amines as starting materials. The generality and scope of this mild method are demonstrated with a wide variety of substrates to furnish functionalized 2-aminoindoles in good yields. The synthetic power of this strategy is further exemplified in the concise synthesis of biologically important alkaloids, Phaitanthrin E and Tryptanthrin.