Iodine/tert‐Butyl Hydroperoxide‐Mediated Reaction of Indoles with Dimethylformamide/Dimethylacetamide to Synthesize Bis‐ and Tris(indolyl)methanes

Here we report a metal-free iodine/tert-butyl hydroperoxide mediated reaction of N-substituted indoles with dimethylformamide (DMF) / dimethylacetamide (DMA). The reaction produces bis- and tris(indolyl)methanes (BIMs and TIMs), in which DMF/DMA provides the methylene (of BIMs) and methine carbons (of TIMs). We have established different optimized conditions for their synthesis. Iodine (10 mol %) with TBHP (in decane, 1.0 equivalent) in DMF/DMA at 130 °C is required for the BIMs synthesis, whereas iodine (20 mol %) with TBHP (in water, 3.0 equivalent) in DMF-H2O or DMA-H2O (9:1) is needed for the TIMs. This methodology could be used to synthesize a variety of BIMs and TIMs. We believe, this is the first report of their metal-free synthesis through C−H functionalization using one carbon source. The use of inexpensive, metal-free and environmentally benign catalyst made the method handy.