Green Approach of Solvent- and Catalyst Free Synthesis of Bis(indolyl)methanes under Visible Light Irradiation

An efficient procedure has been developed for the synthesis of bis(indolyl)methanes (3a-m) from condensation of indole (1) and various substituted aromatic aldehydes (2a-m) is described. The aromatic electrophilic substitution reactions of indole (1) with and various substituted aromatic aldehydes (2a-m) are achieved in solvent- and catalyst free condition using irradiation with 150W tungsten lamp (visible light irradiation). This methodology offers several advantages such as good yields, simple procedure, mild and environmentally benign conditions.