A General Method for the Synthesis of 3,3-bis(indol-3-yl)indolin-2-ones, bis(indol-3-yl)(aryl)methanes and tris(indol-3-yl)methanes Using Naturally Occurring Mandelic Acid as an Efficient Organo-catalyst in Aqueous Ethanol at Room Temperature

A simple, facile, straightforward and environmentally benign protocol has been developed for the efficient synthesis of pharmaceutically interesting 3,3-bis(indol-3-yl)indolin-2-ones, bis(indol- 3-yl)(aryl)methanes and tris(indol-3-yl)methanes using a catalytic amount of mandelic acid as an efficient, naturally occurring, low-cost, commercially available organo-catalyst in aqueous ethanol at room temperature.