Divergent electrosynthesis of 3-iodoindoles and indoles from 2-ethynylanilines under ambient and aqueous conditions

Abstract

A mild and simple electrochemical system has been developed for efficient cyclization of 2-ethynylanilines, employing potassium iodide as the only additive in a non-volatile aqueous solvent. Notably, by altering the electrode material and charge passed, either 3-iodoindoles or indoles can be selectively furnished in high efficiency with a broad substrate scope and good functional group compatibility. The synthetic potential was demonstrated with several examples of late-stage functionalization, gram-scale synthesis and further derivatization. Apart from the key anodic events, cathodic generation of base (HO⁻) from reduction of water was indicated from mechanistic studies to also play a crucial role in these efficient conversions.