Electro-driven Dioxygenation of Indole by Iron Porphyrin with Faradaic Efficiency Exceeding 10 4 %

The selective dioxygenation of indoles by heme enzymes is a significant biochemical process. Synthetic Fe II porphyrins were used to catalyze indole dioxygenation, but the formation of μ-oxo-bridged Fe III –O–Fe III caused catalyst deactivation. Herein, we report a homogeneous electro-driven strategy to realize catalytic indole dioxygenation by Fe tetra(pentafluorophenyl)porphyrin with a turnover number up to 8825 and Faradaic efficiency exceeding 10 4 %. In homogeneous catalysis, inert Fe III –O–Fe III, which is generated upon the oxidation of Fe II porphyrin by Fe III -superoxo and/or Fe IV ═O, can be electrochemically reduced to Fe II porphyrin to reinitiate catalysis. Moreover, we identified an intermediate formed between Fe III -superoxo and dimethylindole by in situ electrochemical mass spectrometry.