Domino Approach to 1-Aminoindoles from 2-Halophenylacetylenes

Significance

Reported is the synthesis of 1-aminoindoles 3 via a palladium-catalyzed domino C-N coupling-5-endo-dig cyclization strategy. The reaction is equally tolerant of EDGs and EWGs on the haloarene (R^¹). Additionally, both alkyl and aryl acetylenes (R^²) were shown to participate efficiently in the reaction, although slightly lower yields were obtained with alkyl substituents. A wide range of both electron-rich and -poor hydrazines, including N-amino heterocycles, were shown to give the aminoindole products in excellent yields.