Electrochemical Activation of C−C Bonds through Mediated Hydrogen Atom Transfer Reactions. Issue 6 (23rd February 2022)

• Record Type: Journal Article
• Authors: Yan, Bing; Shi, Changxia; Beckham, Gregg T.; Chen, Eugene Y.‐X.; Román‐Leshkov, Yuriy
• Is Part Of: ChemSusChem. Volume 15:Issue 6(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-23
• Subjects: C−C bond activation -- electrocatalysis -- plastic upcycling -- radical chemistry -- redox mediators; Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.202102317
• Languages: English
• ISSNs: 1864-5631

Abstract

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 (OS510 ; M n =510 Da) and polystyrene (PS; M n ≈10 000 Da) are converted into oxygenated monomers, dimers, and oligomers. Abstract : An electrochemical approach is developed to activate inert C−C bonds. A redox mediator‐NHPI as the reduced form and PINO as the oxidized form‐extracts benzylic C−H, affording a carbon radical intermediate, which is readily captured by O2 and then converted into oxygenated products. The method is used to deconstruct polystyrene (10 kDa) into monomers, dimers, and oligomers.