We subsequently carried out a series of experiments to unravel the intricacies of the reaction mechanism, presenting our findings in Scheme 3. Our initial step involved conducting the reaction under optimized conditions while introducing TEMPO (4 equiv), a well-known radical scavenger. Notably, the reactivity was entirely quenched, and adduct 23 was identified via HRMS, confirming the presence of radical species. Parallelly, a reaction utilizing an electrondeficient olefin, namely dimethyl maleate, afforded product 24 (25% NMR yield) alongside product 3, further underlining the likely intermediacy of an α-oxyalkyl radical through a chlorine-mediated HAT step (Scheme 3A). Next, Kinetic Isotope Effect (KIE) evaluations, through both competitive and parallel approaches , consistently presented a value approximating 1. This suggests that the Hydrogen Atom Transfer (HAT) is not the ratedetermining step (Scheme 3B). A proposed reaction mechanism, illustrated in Scheme 3C, has been derived from these mechanistic observations. Initially, a chloride ligand associates with the iron center, and upon absorbing purple light, excites the complex to a higher energy state. This is followed by the homolysis of the Fe-Cl bond, generating a chlorine radical and a reduced Fe II species (21). The reduced catalyst is then oxidized at the anode, resulting in the formation of the Fe III center, which closes the catalytic cycle. Iron plays a pivotal role in this transformation. In the absence of iron, we still observe product formation, however, it is accompanied by a substantial production of molecular chlorine, resulting in the unwanted chlorination of pyrazole substrates.