Acid Catalysis via Acid-Promoted Electron Transfer

This feature article focuses on acid catalysis in various redox reactions of not only organic compounds but also metal complexes, in particular metal-oxygen complexes via acid-promoted electron transfer (APET). On the other hand, proton-coupled electron transfer (PCET) has been extensively studied in relation with important biological PCET reactions such as O₂ reduction in respiration and water oxidation in photosynthesis. Because PCET is normally defined as simultaneous electron and proton transfer from the same substrate, acid-promoted electron transfer using external acids is called APET in this article. Various types of chemical transformations exhibiting acid catalysis via APET discussed in this article include C-C bond formation, C-H bond oxidation, aromatic hydroxylation, and oxygen atom transfer reactions such as sulfoxidation and epoxidation reactions.