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1. The “Net” Impact of Hydrothermal Venting on Oceanic Elemental Inventories: Contributions to Plume Geochemistry from the International GEOTRACES Program

   https://doi.org/10.5670/oceanog.2024.421  

   Fitzsimmons, Jessica; Steffen, Janelle (June 2024, Oceanography)

   Hydrothermal vents serve as a primary interface between the cold deep ocean and the warm oceanic crust. While early research showed that seawater-​rock interactions add to or remove elements from seawater during the generation of hydrothermal fluids, consideration of these fluid fluxes alone does not relay the total impact that hydrothermal systems have on seawater geochemistry. In addition, hydrothermal plumes, areas where hydrothermal fluids mix with ocean waters, are host to a range of particle precipitation and scavenging reactions that further modify gross hydrothermal fluid fluxes to define the total “net” hydrothermal impact on oceanic inventories. Here, we review the major discoveries made by the international GEOTRACES program regarding the geochemical transformations occurring within hydrothermal plumes. We classify each element into one of five categories based on its behavior in hydrothermal plumes, a spectrum spanning the geochemical mass balance between net hydrothermal source fluxes and net hydrothermal plume scavenging sinks. Overall, we celebrate the role that GEOTRACES has played in defining the extent and dynamics of hydrothermal plume geochemistry, which is a crucial lever for determining global hydrothermal impacts. 

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2. Highly Efficient and Stereoselective Thioallylation of Alkynes: Possible Gold Redox Catalysis with No Need for a Strong Oxidant

   https://doi.org/10.1002/anie.201802540  

   Wang, Jin; Zhang, Shuyao; Xu, Chang; Wojtas, Lukasz; Akhmedov, Novruz G.; Chen, Hao; Shi, Xiaodong (May 2018, Angewandte Chemie International Edition)

   Abstract Stereoselective thioallylation of alkynes under possible gold redox catalysis was accomplished with high efficiency (as low as 0.1 % catalyst loading, up to 99 % yield) and broad substrate scope (various alkynes, inter‐ and intramolecular fashion). The gold(I) catalyst acts as both a π‐acid for alkyne activation and a redox catalyst for Au^I/IIIcoupling, whereas the sulfonium cation generated in situ functions as a mild oxidant. This novel methodology provides an exciting system for gold redox catalysis without the need for a strong oxidant. 

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3. Evidence for diffusing atomic oxygen uncovered by separating reactants with a semi-permeable nanocapsule barrier

   https://doi.org/10.1039/C8CC06715E  

   Omlid, Sara M.; Dergunov, Sergey A.; Isor, Ankita; Sulkowski, Kathryn L.; Petroff, John T.; Pinkhassik, Eugene; McCulla, Ryan D. (February 2019, Chemical Communications)

   Ground-state atomic oxygen [O( 3 P)] is an oxidant whose formation in solution was proposed but never proven. Polymer nanocapsules were used to physically separate dibenzothiophene S-oxide (DBTO), a source of O( 3 P), from an O( 3 P)-accepting molecule. Irradiation of polymer nanocapsules loaded with DBTO resulted in oxidation of the O( 3 P)-acceptor placed outside nanocapsules. The results rule out a direct oxygen atom transfer mechanism and are consistent with freely diffusing O( 3 P) as the oxidant. 

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4. Kinetics‐Based Approach to Developing Electrocatalytic Variants of Slow Oxidations: Application to Hydride Abstraction‐Initiated Cyclization Reactions

   https://doi.org/10.1002/chem.202200335  

   Lawrence, Jean‐Marc_I_A; Floreancig, Paul_E (March 2022, Chemistry – A European Journal)

   Abstract Electrochemical oxidant regeneration is challenging in reactions that have a slow redox step because the steady‐state concentration of the reduced oxidant is low, causing difficulties in maintaining sufficient current or preventing potential spikes. This work shows that applying an understanding of the relationship between intermediate cation stability, oxidant strength, overpotential, and concentration on reaction kinetics delivers a method for electrochemical oxoammonium ion regeneration in hydride abstraction‐initiated cyclization reactions, resulting in the development of an electrocatalytic variant of a process that has a high oxidation transition state free energy. This approach should be applicable to expanding the scope of electrocatalysis to include additional slow redox processes. 

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5. Ligand-enabled ortho -C–H olefination of phenylacetic amides with unactivated alkenes

   https://doi.org/10.1039/c7sc04827k  

   Lu, Ming-Zhu; Chen, Xing-Rong; Xu, Hui; Dai, Hui-Xiong; Yu, Jin-Quan (January 2018, Chemical Science)

   Although chelation-assisted C–H olefination has been intensely investigated, Pd( ii )-catalyzed C–H olefination reactions are largely restricted to acrylates and styrenes. Here we report a quinoline-derived ligand that enables the Pd( ii )-catalyzed olefination of the C(sp 2 )–H bond with simple aliphatic alkenes using a weakly coordinating monodentate amide auxiliary. Oxygen is used as the terminal oxidant with catalytic copper as the co-oxidant. A variety of functional groups in the aliphatic alkenes are tolerated. Upon hydrogenation, the ortho -alkylated product can be accessed. The utility of this reaction is also demonstrated by the late-stage diversification of drug molecules. 

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