Oxidative cleavage of alkenes is a fundamental transformation that has been heavily utilized in the field of synthetic organic chemistry to obtain key carbonyl functional groups found in natural products and drug candidates. Additionally, oxidation of alkenes is frequently noted in pharmaceutical, agrochemical, and material synthesis. Gaseous ozone (O<sub>3</sub>) is commonly implemented to achieve oxidative cleavage of alkenes via ozonolysis despite safety and environmental concerns. Other complementary approaches utilize strong oxidants like molecular oxygen and toxic transition metals such as ruthenium, osmium, or manganese, all of which share many of the same limitations as ozonolysis. Owing to the lack of sustainable alternatives, these methods are still prevalent in synthesis. Therefore, developing safer and sustainable processes for these essential oxidation reactions is highly warranted.<br/><br/>We report a novel alternative to ozonolysis via the anaerobic conversion of alkenes into carbonyl moieties through visible light-promoted oxygen-atom transfer from nitroarenes. The reaction relies on direct photoexcitation of a nitroarene using low energy visible light. The photoexcited nitroarene has been shown to interact with alkenes, cleanly transferring its oxygen atoms to give the corresponding aldehyde and ketone products (Scheme 1). Notably, the method does not require harsh UV-light or the use of strong exogenous oxidants. This method anaerobically cleaves a wide range of substituted aryl and alkyl alkenes in good to excellent yields. Mechanistic studies using UV-visible spectroscopy revealed that this method occurs via a solvent separated ion-pair, where the nitroarene undergoes photoexcitation to generate a triplet diradical species that subsequently undergoes cyclization with alkenes to generate the putative dioxazolidine intermediate. Multinuclear PhotoNMR spectroscopy has shown evidence for this intermediate, which undergoes rapid fragmentation to give the carbonyl-containing products. Overall, this reaction overcomes the limitations of widely used oxidative cleavage methods, including ozonolysis, and provides a safe, practical protocol for the synthetic community.

Photoinduced oxygen transfer using nitroarenes for the anaerobic cleavage of alkenes

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