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1. 1,2-Hydrogen atom transfer of aminyl radicals under photoredox catalysis for the synthesis of α-amino phosphine oxides

   https://doi.org/10.1039/D5SC00268K  

   Pan, Ailin; Rotella, Madeline E; Meng, Yamiao; Tian, Xun; Duan, Shengzu; Jiang, Yonggang; Deng, Guogang; Limburg, Bart; Zhang, Hongbin; Kozlowski, Marisa C; et al (January 2026, Chemical Science)

   Photocatalytic 1,2-HAT of N-centered radicals leads to C-centered α-amino radicals, with trapping by phosphine oxides to access α-amino phosphine oxides. Mechanistic experiments and DFT calculations support a 1,2-HAT pathway. 

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2. Remote C–H Functionalization via Selective Hydrogen Atom Transfer

   https://doi.org/10.1055/s-0036-1591930  

   Stateman, Leah; Nakafuku, Kohki; Nagib, David (April 2018, Synthesis)

   The selective functionalization of remote C–H bonds via intramolecular hydrogen atom transfer (HAT) is transformative for organic synthesis. This radical-mediated strategy provides access to novel reactivity that is complementary to closed-shell pathways. As modern methods for mild generation of radicals are continually developed, inherent selectivity paradigms of HAT mechanisms offer unparalleled opportunities for developing new strategies for C–H functionalization. This review outlines the history, recent advances, and mechanistic underpinnings of intramolecular HAT as a guide to addressing ongoing challenges in this arena. 1 Introduction 2 Nitrogen-Centered Radicals 2.1 sp3 N-Radical Initiation 2.2 sp2 N-Radical Initiation 3 Oxygen-Centered Radicals 3.1 Carbonyl Diradical Initiation 3.2 Alkoxy Radical Initiation 3.3 Non-alkoxy Radical Initiation 4 Carbon-Centered Radicals 4.1 sp2 C-Radical Initiation 4.2 sp3 C-Radical Initiation 5 Conclusion 

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3. An Overview of α‐Aminoalkyl Radical Mediated Halogen‐Atom Transfer

   https://doi.org/10.1002/cctc.202300860  

   Sachidanandan, Krishnakumar; Niu, Ben; Laulhé, Sébastien (September 2023, ChemCatChem)

   Abstract The merging of photocatalysis with halogen‐atom transfer (XAT) processes has proven to be a versatile tool for the generation of carbon‐centered radicals in organic synthesis. XAT processes are unique in that they generate radicals without requiring the use of strong reductants necessary for the traditional single electron transfer (SET) activation of halides. Pathways to achieve XAT in synthetic applications can be categorized into three major sections: i) heteroatom‐based activators, ii) metal‐based activators, and iii) carbon‐based activators among which α‐aminoalkyl radicals have taken the center stage. Access to these α‐aminoalkyl radicals as XAT reagents has gained significant attention in the past few years due to the robustness of the reactions, the simplicity of the reagents required, and the broadness of their applications. Generation of these α‐aminoalkyl radicals is simply achieved through the single electron oxidation of tertiary amines, which after deprotonation at the α‐position generates the α‐aminoalkyl radicals. Due to the wide scope of tertiary amines available and the tunable nucleophilicity of α‐aminoalkyl radical formed, this strategy has become an attractive alternative to heteroatom/metal‐based radicals for XAT. In this minireview, we focus our attention on recent (2020–2023) developments and uses of this robust technology to mediate XAT processes. 

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4. Wildfire particulate matter as a source of environmentally persistent free radicals and reactive oxygen species

   https://doi.org/10.1039/D2EA00170E  

   Fang, Ting; Hwang, Brian C.; Kapur, Sukriti; Hopstock, Katherine S.; Wei, Jinlai; Nguyen, Vy; Nizkorodov, Sergey A.; Shiraiwa, Manabu (March 2023, Environmental Science: Atmospheres)

   Wildfires, which have been occurring increasingly in the era of climate change, emit massive amounts of particulate matter (PM) into the atmosphere, strongly affecting air quality and public health. Biomass burning aerosols may contain environmentally persistent free radicals (EPFRs, such as semiquinone radicals) and redox-active compounds that can generate reactive oxygen species (ROS, including ·OH, superoxide and organic radicals) in the aqueous phase. However, there is a lack of data on EPFRs and ROS associated with size-segregated wildfire PM, which limits our understanding of their climate and health impacts. We collected size-segregated ambient PM in Southern California during two wildfire events to measure EPFRs and ROS using electron paramagnetic resonance spectroscopy. EPFRs are likely associated with soot particles as they are predominantly observed in submicron particles (PM 1 , aerodynamic diameter ≤ 1 μm). Upon extraction in water, wildfire PM mainly generates ·OH (28–49%) and carbon-centered radicals (∼50%) with minor contributions from superoxide and oxygen-centered organic radicals (2–15%). Oxidative potential measured with the dithiothreitol assay (OP-DTT) is found to be high in wildfire PM 1 , exhibiting little correlation with the radical forms of ROS ( r 2 ≤ 0.02). These results are in stark contrast with PM collected at highway and urban sites, which generates predominantly ·OH (84–88%) that correlates well with OP-DTT ( r 2 ∼ 0.6). We also found that PM generated by flaming combustion generates more radicals with higher OP-DTT compared to those by smoldering or pyrolysis. 

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5. Plastic burning particulate matter as a source of environmentally persistent free radicals and reactive oxygen and chlorine species

   https://doi.org/10.1038/s44407-025-00015-8  

   Salim, Rizana; Kapur, Sukriti; Schervish, Meredith; Gerritz, Lena; Edwards, Kasey_C; Ruis-Armenta, Luis; Varghese, Emil; Ravikrishna, Raghunathan; Nizkorodov, Sergey_A; Gunthe, Sachin_S; et al (June 2025, npj Clean Air)

   Abstract Burning plastic waste releases massive amounts of atmospheric particulate matter (PM), but its chemical composition and health-related properties are largely unelucidated. Here we characterize chemical composition of PM generated from burning common types of plastics and quantify reactive oxygen/chlorine species and PM oxidative potential (OP). We find that plastic burning PM contains high levels of environmentally persistent free radicals (EPFRs), transition metals, and polycyclic aromatic hydrocarbons. In the aqueous phase, PM generates hydrogen peroxide, •OH radicals, and carbon-centered organic radicals, exhibiting high levels of OP as characterized by dithiothreitol (DTT) and OH assays. Remarkably, plastic burning PM is associated with high concentrations of hypochlorous acid. Kinetic model simulations demonstrate that the PM respiratory deposition leads to •OH formation via complex redox reactions among its constituents and antioxidants in lung lining fluid. Our study highlights significant atmospheric and health implications for unregulated plastic burning, particularly common in many areas of developing countries. 

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