Iron-Catalyzed LMCT Photochemical Witkop Oxidation under Visible-Light

N-Acetylaminoacetophenone derivatives are relevant intermediates in organic synthesis and drug discovery and are commonly obtained through the Witkop oxidation¹ of indole derivatives.² Despite their high commercial value, classical methods for this transformation generally rely on hazardous reagents, such as chromic acid, peracids, hypervalent iodine compounds, ozone, or toxic transition metals.³ Recent advances in visible-light photochemistry illustrate the potential of light-driven strategies to enable milder oxidative processes.⁴ In this context, strategies based on ligand-to-metal charge transfer (LMCT) enable the in situ generation of reactive species from earth-abundant metal catalysts, such as iron, and they have emerged as promising alternatives. In this work, an LMCT-based photocatalytic methodology for the Witkop oxidation is reported, employing iron as the catalyst under visible-light irradiation for the synthesis of N-acetylaminoacetophenone derivatives in yields of up to 94%. Under the optimized conditions, substrate scope evaluation and mechanistic investigations are currently underway and will be presented.