Tunnelling assisted hydrogen elimination mechanisms of FeCl3/TEMPO.

Metal-TEMPO hybrids are a family of novel and promising catalysts for aerobic oxidation of alcohols, yet the underlying mechanisms have not been understood theoretically. Using density functional theory, we probe the hydrogen abstraction mechanisms of FeCl3/TEMPO on two characteristic substrates, 9,10-dihydroanthracene and benzyl alcohol. We found that the low spin state of FeCl3/TEMPO is more favourable, and that the N atom is the preferred hydrogen acceptor. Moreover, dispersion interactions assist the reaction, as well as nuclear tunnelling, which even at room temperature can speed up the process by almost two orders of magnitude. We also predict that pronounced kinetic isotope effects (KIE) could be observed due to tunnelling. Our findings provide insights into improving the substrate scope and the development of new transformations for the FeCl3/TEMPO system.

Citation

Shi-Jun Li, Wei Fang, Jeremy O Richardson, De-Cai Fang. Tunnelling assisted hydrogen elimination mechanisms of FeCl3/TEMPO. Chemical communications (Cambridge, England). 2022 Jan 06;58(4):565-568

PMID: 34909806

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