Efficient synthesis of bis- and tris-indolylalkanes catalyzed by a Bronsted acid-surfactant catalyst in water

A simple and efficient synthesis of bis- and tris-indolylalkanes from carbonyls (aldehydes/ketones) and indoles with excellent yields in the presence of dodecylsulphonic acid (DSA) in water at room temperature is described. The catalyst is also applicable for the synthesis of 3,3-di(3-indolyl)oxindoles. The dodecylsulphonic acid acts as both Brnsted acid and surface-active agent in the reaction mixture.