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1. Organophotoredox/Palladium Dual Catalytic Decarboxylative Csp ³ -Csp ³ Coupling of Carboxylic Acids and π-Electrophiles

   https://doi.org/10.1039/D0SC02609C  

   Cartwright, Kaitie C; Tunge, Jon (January 2020, Chemical Science)

   A dual catalytic decarboxylative allylation and benzylation method for the construction of new C(sp 3 )–C(sp 3 ) bonds between readily available carboxylic acids and functionally diverse carbonate electrophiles has been developed. The new process is mild, operationally simple, and has greatly improved upon the efficiency and generality of previous methodology. In addition, new insights into the reaction mechanism have been realized and provide further understanding of the harnessed reactivity. 

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2. Direct Aroylation of Olefins through a Cobalt/Photoredox‐Catalyzed Decarboxylative and Dehydrogenative Coupling with α‐Oxo Acids

   https://doi.org/10.1002/chem.202202781  

   Davies, Alex_M; D_Hernandez, Rafael; Tunge, Jon_A (November 2022, Chemistry – A European Journal)

   Abstract A photoredox/cobalt dual catalytic procedure has been developed that allows benzoylation of olefins. Here the photoredox catalyst effects the decarboxylation of α‐ketoacids to form benzoyl radicals. After addition of this radical to styrenes, the cobalt catalyst abstracts a H‐atom. Hydrogen evolution from the putative cobalt hydride intermediate allows a Heck‐like aroylation without the need for a stoichiometric oxidant. Mechanistic studies reveal that electronically different styrenes lead to a curved Hammett plot, thus suggesting a change in product‐determining step in the catalytic mechanism. 

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3. Catalytic Chemo‐ and Regioselective Radical Carbocyanation of 2‐Azadienes for the Synthesis of α‐Amino Nitriles

   https://doi.org/10.1002/anie.202300605  

   Duan, Shengzu; Du, Ya; Wang, Lingling; Tian, Xun; Zi, Yujin; Zhang, Hongbin; Walsh, Patrick J.; Yang, Xiaodong (March 2023, Angewandte Chemie International Edition)

   Abstract α‐Amino nitriles are versatile structural motifs in a variety of biologically active compounds and pharmaceuticals and they serve as valuable building blocks in synthesis. The preparation of α‐ and β‐functionalized α‐amino nitriles from readily available scaffolds, however, remains challenging. Herein is reported a novel dual catalytic photoredox/copper‐catalyzed chemo‐ and regioselective radical carbocyanation of 2‐azadienes to access functionalized α‐amino nitriles by using redox‐active esters (RAEs) and trimethylsilyl cyanide. This cascade process employs a broad scope of RAEs and provides the corresponding α‐amino nitrile building blocks in 50–95 % yields (51 examples, regioselectivity >95 : 5). The products were transformed into prized α‐amino nitriles and α‐amino acids. Mechanistic studies suggest a radical cascade coupling process. 

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4. Stereoselective amino acid synthesis by synergistic photoredox-pyridoxal radical biocatalysis

   https://doi.org/10.1126/science.adg2420  

   Cheng, Lei; Li, Dian; Mai, Binh Khanh; Bo, Zhiyu; Cheng, Lida; Liu, Peng; Yang, Yang (July 2023, Science)

   Developing synthetically useful enzymatic reactions that are not known in biochemistry and organic chemistry is an important challenge in biocatalysis. Through the synergistic merger of photoredox catalysis and pyridoxal 5′-phosphate (PLP) biocatalysis, we developed a pyridoxal radical biocatalysis approach to prepare valuable noncanonical amino acids, including those bearing a stereochemical dyad or triad, without the need for protecting groups. Using engineered PLP enzymes, either enantiomeric product could be produced in a biocatalyst-controlled fashion. Synergistic photoredox-pyridoxal radical biocatalysis represents a powerful platform with which to discover previously unknown catalytic reactions and to tame radical intermediates for asymmetric catalysis. 

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5. Photocatalytic decarboxylative amidosulfonation enables direct transformation of carboxylic acids to sulfonamides

   https://doi.org/10.1039/d1sc01389k  

   Nguyen, Vu T.; Haug, Graham C.; Nguyen, Viet D.; Vuong, Ngan T.; Arman, Hadi D.; Larionov, Oleg V. (January 2021, Chemical Science)

   null (Ed.)

   Sulfonamides feature prominently in organic synthesis, materials science and medicinal chemistry, where they play important roles as bioisosteric replacements of carboxylic acids and other carbonyls. Yet, a general synthetic platform for the direct conversion of carboxylic acids to a range of functionalized sulfonamides has remained elusive. Herein, we present a visible light-induced, dual catalytic platform that for the first time allows for a one-step access to sulfonamides and sulfonyl azides directly from carboxylic acids. The broad scope of the direct decarboxylative amidosulfonation (DDAS) platform is enabled by the efficient direct conversion of carboxylic acids to sulfinic acids that is catalyzed by acridine photocatalysts and interfaced with copper-catalyzed sulfur–nitrogen bond-forming cross-couplings with both electrophilic and nucleophilic reagents. 

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