Facile synthesis of 3-substituted indoles containing highly polarized double bonds

In this paper, an effective procedure is described for the synthesis of novel indoles containing highly polarized double bonds. The strategy involves the preparation of (indolylmethyl)malononitriles via the one-pot three-component reaction of an aldehyde, malononitrile and indole in the presence of Zn(OAc)2/NaOAc under silent and ultrasonic conditions. The reaction further proceeds through oxidative elimination under solvent-free conditions in the presence of Ca(OCl)2 to furnish indolylacrylonitriles in high yields and short reaction times.