Electrochemical Activation of C−C Bonds through Mediated Hydrogen Atom Transfer Reactions

Abstract Activating inert sp 3 –sp 3 carbon‐carbon (C−C) bonds remains a major bottleneck in the chemical upcycling of recalcitrant polyolefin waste. In this study, redox mediators are used to activate the inert C−C bonds. Specifically, N ‐hydroxyphthalimide (NHPI) is used as the redox mediator, which is oxidized to phthalimide‐ N ‐oxyl (PINO) radical to initiate hydrogen atom transfer (HAT) reactions with benzylic C−H bonds. The resulting carbon radical is readily captured by molecular oxygen to form a peroxide that decomposes into oxygenated C−C bond‐scission fragments. This indirect approach reduces the oxidation potential by >1.2 V compared to the direct oxidation of the substrate. Studies with model compounds reveal that the selectivity of C−C bond cleavage increases with decreasing C−C bond dissociation energy. With NHPI‐mediated oxidation, oligomeric styrene (OS 510 ; M n =510 Da) and polystyrene (PS; M n ≈10 000 Da) are converted into oxygenated monomers, dimers, and oligomers.