An ultrasound-promoted green approach for the synthesis of 3-(indol-3-yl)-3-hydroxyindolin-2-ones catalyzed by Fe(III)

Ferric chloride hexahydrate was used as a recyclable homogeneous catalyst in aqueous media for the synthesis of 3-(indol-3-yl)-3-hydroxyindolin-2-ones under sonication. It was found that the employed conditions afford the products smoothly in good to excellent yields.