Facile access to 2-hydroxy-2-substituted indole-3-ones via a copper-catalyzed oxidative cyclization of 2-arylethynylanilines.

ABSTRACT

This paper reports a practical and versatile oxidative cyclization of 2-arylethynylanilines towards 2-hydroxy-2-substituted indol-3-ones via a copper-catalyzed radical approach in the presence of O2. The transformation of 2-hydroxy-2-arylindol-3-ones to 3-hydroxy-3-arylindol-2-ones proceeds well with good yields and highlights the practicability and utility of this catalytic system. Mechanistic investigations showed that the acetyl substituent on 2-arylaethynylanilines played an important role in the formation of the cyclic products and the reaction proceeded via an N-center radical-based 5-endo-dig aza-cyclization pathway.