Green Synthesis of Primary Aniline-Based Indolylmethanes via One-Pot Aza-Friedel-Crafts Reaction Catalyzed by Brønsted Acidic Ionic Liquid in Aqueous Media.

A green, convenient, and metal-free methodology for synthesizing primary aniline-based indolylmethanes has been developed through a sequential one-pot, three-component aza-Friedel-Crafts reaction. This approach employs a wide range of commercially available aldehydes, primary anilines, and indoles, catalyzed by a Brønsted acidic ionic liquid in an aqueous medium. A variety of desirable products were obtained in high yields (up to 98%). The process was successfully demonstrated on a gram scale, confirming its scalability and reproducibility while maintaining high yields. Additionally, the catalyst exhibited remarkable recyclability, retaining high catalytic efficiency over three cycles without a significant loss of activity.