A [4+1] Cyclative Capture Approach to 3H-Indole-N-oxides at Room Temperature by Rhodium(III)-Catalyzed CH Activation

Abstract

The rhodium(III)-catalyzed [3+2] CH cyclization of aniline derivatives and internal alkynes represents a useful contribution to straightforward synthesis of indoles. However, there is no report on the more challenging synthesis of pharmaceutically important N-hydroxyindoles and 3H-indole-N-oxides. Reported herein is the first rhodium(III)-catalyzed [4+1] CH oxidative cyclization of nitrones with diazo compounds to access 3H-indole-N-oxides. More significantly, this reaction proceeds at room temperature and has been extended to the synthesis of N-hydroxyindoles and N-hydroxyindolines.

Keywords: CH activation; cyclizations; diazo compounds; heterocycles; rhodium.