FeCl3 catalyzed intermolecular reaction between enol ethers and anilines: Access to 2,3-substituted indoles through aryl group migration

An intermolecular FeCl3 catalyzed reaction between anilines and enol ethers is described. A variety of enol ethers and aromatic amines undergo a C-C bond formation followed by cyclization via C-N bond formation to afford the 2,3-disubstituted indoles, involving an unexpected aryl group migration. In this methodology, anilines act as bis-nucleophiles, wherein the initial attack occurs at the alpha-position of enol ether from the ortho position of aniline followed by the subsequent reaction of the amine moiety of aniline at the beta-position, leading to the indole framework. This method is simple, obviates the use of expensive/hazardous transition-metal catalysts, and offers a wide range of substrate scope. (C) 2020 Elsevier Ltd. All rights reserved.