Model could improve promising C–H activation

Abstract

Chemists recently found a C–H activation reaction that worked surprisingly well with relatively weak oxidants. Now their colleagues have made a theoretical model that can explain the reaction’s dynamics (J. Am. Chem. Soc. 2018, DOI: 10.1021/jacs.8b10461). The reaction uses intramolecular proton-coupled electron transfer (PCET), in which an oxidant extracts one electron from the C–H bond as a benzoate oxygen positioned nearby grabs the resulting proton, leaving a carbon radical where new substituents can bind. Yale University’s Sharon Hammes-Schiffer, whose group studies PCET reactions, found that the reaction happens by a simultaneous energy-releasing tunneling of the proton and electron between energy states, explaining why the oxidant has relatively little effect on the reaction’s speed. The Yale group also discovered that the H and O atoms start farther apart than thought, which means twisting them into position incurs an energy penalty. Redesigning the molecule to avoid that conformation change could ...