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1. Nickel‐Catalyzed C( sp ² )−C( sp ³ ) Kumada Cross‐Coupling of Aryl Tosylates with Alkyl Grignard Reagents

   https://doi.org/10.1002/adsc.201801586  

   Piontek, Aleksandra; Ochędzan‐Siodłak, Wioletta; Bisz, Elwira; Szostak, Michal (April 2019, Advanced Synthesis & Catalysis)

   Abstract Aryl tosylates are an attractive class of electrophiles for cross‐coupling reactions due to ease of synthesis, low price, and the employment of C−O electrophiles, however, the reactivity of aryl tosylates is low. Herein, we report the Ni‐catalyzed C(sp²)−C(sp³) Kumada cross‐coupling of aryl tosylates with primary and secondary alkyl Grignard reagents. The method delivers valuable alkyl arenes by cross‐coupling with challenging alkyl organometallics possessing β‐hydrogens that are prone to β‐hydride elimination and homo‐coupling. The reaction is catalyzed by an air‐ and moisture stable‐Ni(II) precatalyst. A broad range of electronically‐varied aryl tosylates, including bis‐tosylates, underwent this transformation, and many examples are suitable at mild room temperature conditions. The combination of Ar−X cross‐coupling with the facile Ar−OH activation/cross‐coupling strategy permits for orthogonal cross‐coupling with challenging alkyl organometallics. Furthermore, we demonstrate that the method operates with TON reaching 2000, which is one of the highest turnovers observed to date in Ni‐catalyzed cross‐couplings. magnified image 

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2. Reductive Alkylation of 2-Bromoazoles via Photoinduced Electron Transfer: A Versatile Strategy to C sp ² –C sp ³ Coupled Products

   https://doi.org/10.1021/acs.orglett.5b01711  

   Arora, Amandeep; Teegardin, Kip A.; Weaver, Jimmie D. (July 2015, Organic Letters)

   null (Ed.)
3. Stereoretentive C( sp ³ )–S Cross-Coupling

   https://doi.org/10.1021/jacs.8b11211  

   Zhu, Feng; Miller, Eric; Zhang, Shuo-qing; Yi, Duk; O’Neill, Sloane; Hong, Xin; Walczak, Maciej A. (December 2018, Journal of the American Chemical Society)
4. Recyclable All‐in‐One Organo‐Photo‐Auxiliaries Enabling ( sp ³ )C−( sp ³ )C Coupling Reactions with Diverse Functionalities

   https://doi.org/10.1002/adsc.202400899  

   Maharjan, Samjhana; Dakoju, Ravi_Kishore; Albano, Bella; Ondiek, Pamela_A; O'Shea, Joseph_M; Cosme‐Hernandez, Angel_G; Wink, Donald; Pemberton, Barry_C; Lopez, Steven_A; Ayitou, A_Jean‐Luc (November 2024, Advanced Synthesis & Catalysis)

   Abstract Photochemical C−C coupling reactions can be tailored to industrial chemical processes and preparations of pharmaceuticals. Recent approaches in this area are limited to using precious transition metal coordination complexes that facilitate light absorption and redox processes with benchtop chemicals. Herein, we propose a paradigm that involves all‐in‐one organo‐photo‐auxiliaries,thio‐heteroarenes, which exhibit unique photophysical properties. Thesethio‐heteroarenes were employed to prepare several all‐in‐one ionic photo‐salts from commercially available alkyl/benzyl and heterocyclic halides via aromaticity‐mediated nucleophilic substitution reactions. From the library of >30 salts, we performed on‐demand photochemical C−C coupling reactions to isolate numerous symmetrical and unsymmetrical diary/alkyl‐ethanes with yields up to 84% and mass balance as high as 96%. We also investigated the influence of structural features/properties on the outcomes of the photochemical C−C coupling reactions. The current photochemical C−C method was successful in the isolation of >30 photoproducts, including the natural product Brittonin A, a precursor of Imipramine, and derivatives of the bioactive Honokiol Analogues. Furthermore, transient absorption spectroscopy and time‐dependent density functional theory calculations were used to decipher the nature of light‐promoted electronic transitions. 

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5. Transition-metal-free C(sp ³ )–H/C(sp ³ )–H dehydrogenative coupling of saturated heterocycles with N -benzyl imines

   https://doi.org/10.1039/D0SC00031K  

   Liu, Zhengfen; Li, Minyan; Deng, Guogang; Wei, Wanshi; Feng, Ping; Zi, Quanxing; Li, Tiantian; Zhang, Hongbin; Yang, Xiaodong; Walsh, Patrick J. (January 2020, Chemical Science)

   A unique C(sp 3 )–H/C(sp 3 )–H dehydrocoupling of N -benzylimines with saturated heterocycles is described. Using super electron donor (SED) 2-azaallyl anions and aryl iodides as electron acceptors, single-electron-transfer (SET) generates an aryl radical. Hydrogen atom transfer (HAT) from saturated heterocycles or toluenes to the aryl radical generates alkyl radicals or benzylic radicals, respectively. The newly formed alkyl radicals and benzylic radicals couple with the 2-azaallyl radicals with formation of new C–C bonds. Experimental evidence supports the key hydrogen-abstraction by the aryl radical, which determines the chemoselectivity of the radical–radical coupling reaction. It is noteworthy that this procedure avoids the use of traditional strong oxidants and transition metals. 

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