A Green Method for the Synthesis of Bis(indolyl)methanes, Tris(indolyl)methanes and 3,3ʹʹ-Diindolyloxindole Derivatives Using B-Cyclodextrin Sulfuric Acid in Water

B-Cyclodextrin sulfuric acid as a green Lewis acid catalyst has been applied for the preparation of bis(indolyl)methanes, tris(indolyl)methanes and 3,3ʹ-diindolyloxindole derivatives by the condensation of indoles with various carbonyl compounds in aqueous media with high to excellent yields.