Photo-induced Thiocyanation of Alkenes Catalyzed by Non-heme Iron Complexes: Synthetic Methodology and Mechanistic Insights

Abstract

High valent iron complexes Fe-X have been known to transfer their X group toward carbon radical species to form R–X bond. To utilize this capability of iron catalyst, novel photo-induced iron catalysis system had been developed in the difunctionalization of alkenes in the presence of radical initiator. However, the details of the reaction mechanism are still unclear, especially the transformations of the photocatalyst and the iron catalyst during the catalytic turnover. Herein, we expanded the photo-driven non-heme iron complex catalyzed thiocyanation of styrene substrate. This protocol exhibited broad substrate scope and high efficiency. Detailed mechanistic studies using various spectroscopies, such as UV-vis, mass spectrometry, transient absorption spectroscopy and X-ray absorption spectroscopy, revealed the transformations of photocatalyst [Ir^III(ppy)₃] and group transfer catalyst [Fe^II(bpmen)]²⁺. Real-time spectroscopies combined with mechanistic experiments demonstrated that [Ir^IV(ppy)₃]⁺ and [Fe^III(bpmen)]³⁺ were the key intermediates involved in the reaction cycle.

Keywords

Mechanistic studies / Non-heme iron complex / Photo-induced / Thiocyanation / Spectroscopy

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