Carboxylic Acid Catalyzed Three-Component Aza-Friedel−Crafts Reactions in Water for the Synthesis of 3-Substituted Indoles

The carboxylic acid catalyzed three-component aza-Friedel−Crafts reactions of aldehydes, primary amines, and indoles in water have been developed. The aza-Friedel−Crafts products could be easily transformed to various 3-substituted indoles including biologically active compounds. This system offers a novel efficient method for the synthesis of 3-substituted indoles.