Fe(III)-Driven Metalloradical Catalysis Using Iodonium Ylides as Carbene Precursor for Spiro/Cyclization

Transition metal-catalyzed olefin cyclization via metalloradical catalysis (MRC) is a highly versatile strategy for synthesizing functionalized cyclopropanes and furans. However, mostly diazo compounds have been used as carbene precursors for the formation of metal-carbenoid complexes. These compounds suffer from limitations in their use-their explosive or hazardous nature makes them challenging to work with. Most catalysts employed in MRC to date are airsensitive and demand inert reaction conditions. In this work, we have explored cyclic iodonium ylides as surrogate carbene precursors using air-stable Fe(III)-porphyrin complex, Fe III (TPP)Cl as a metalloradical catalyst for olefin spiro/cyclization to afford cyclopropanes, dihydrofurans, and furans. The mechanistic investigations, along with the DFT studies and electronic structure analysis, reveal that the catalytic process follows a stepwise radical pathway instead of a concerted ionic mechanism. This further confirms that Fe(III) is the active catalyst instead of the in situ reduced Fe(II) analog.