Iron-Catalyzed Sodium Iodide-Promoted Aerobic Oxidative Cross-Coupling of Benzofurans with Indoles

Abstract

Benzofuran-indole heterobiaryls are important structural motifs with widespread applications. However, their synthesis is limited to methods requiring Pd catalysts and prefunctionalized substrates. Herein, we report the first general oxidative cross-coupling of benzofurans with indoles under aerobic, Fe(III)-catalyzed conditions with NaI as a catalytic promoter. The reaction displays wide substrate scope and high chemo- and regioselectivity. Preliminary mechanistic experiments indicate a single-electron-transfer (SET)-based mechanism with radical cation-nucleophile coupling as the crucial bond-forming step.