Synchronous and basic asynchronous hydrogen-atom abstraction of benzylic substrates by high-valent iron–oxo porphyrin species

The unsubstituted iron–oxo porphyrin reacts with unsubstituted benzylic C–H bond substrates via a synchronous HAT mechanism. In contrast, when an electron-rich iron–oxo porphyrin reacts with electron-poor substrates, it follows a basic asynchronous HAT mechanism.