We report a new general method for trapping short-lived radicals, based on a homolytic substitution reaction S2'. This departure from conventional radical trapping by addition or radical-radical cross-coupling results in high sensitivity, detailed structural information, and general applicability of the new approach. The radical traps in this method are terminal alkenes possessing a nitroxide leaving group (, allyl-TEMPO derivatives). The trapping process thus yields stable products which can be stored and subsequently analyzed by mass spectrometry (MS) supported by well-established techniques such as isotope exchange, tandem MS, and high-performance liquid chromatography-MS. The new method was applied to a range of model radical reactions in both liquid and gas phases including a photoredox-catalyzed thiol-ene reaction and alkene ozonolysis. An unprecedented range of radical intermediates was observed in complex reaction mixtures, offering new mechanistic insights. Gas-phase radicals can be detected at concentrations relevant to atmospheric chemistry.
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| http://dx.doi.org/10.1021/jacs.2c03618 | DOI Listing |
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