8. Nickel-catalyzed C(sp2)–C(sp3) coupling via photoactive electron donor–acceptor (EDA) complexes
Salman Alsharif, Chen Zhu, Xiushan Liu, Shao-Chi Lee, Huifeng Yue, Magnus Rueping
Chem. Commun., 2024,
DOI: 10.1039/D4CC00217B
Abstract:
We have developed a novel Ni-catalyzed reductive cross-coupling reaction of aryl bromides and alkyl iodides via a photoactive electron donor–acceptor (EDA) complex. This photo-induced process enables the efficient construction of C(sp2)–C(sp3) bonds in the absence of an external photocatalyst. Electronically and structurally diverse aryl bromides, as well as secondary and primary alkyl iodides could undergo this transformation smoothly. Natural product derivatives were employed successfully, and UV-vis spectroscopy was utilized to gain mechanistic insight.
7. Multiphoton photoredox catalysis enables selective hydrodefluorinations
Jiaqi Jia, Kathiravan Murugesan, Chen Zhu, Huifeng Yue, Shao-Chi Lee, Magnus Rueping
Chinese Chemical Letters 2024, 109866
DOI: 10.1016/j.cclet.2024.109866
Abstract:
Late-stage modification of complex molecules via site-selective hydrodefluorination is a challenging endeavor. The selective activation of carbon-fluorine (C–F) bonds in the presence of multiple C–F bonds is of importance in organic synthesis and drug discovery. Herein, we describe the activation of C-F bonds via multiphoton photoredox catalysis to selectively produces a series of hydrodefluorinated compounds by simply tuning the reaction conditions. Moreover, this protocol was successfully applied to the late-stage functionalization of different drug-derivatives and the corresponding mono-, di-, and tri-defluorinated products were obtained in good to excellent yields. A detailed mechanistic investigation provides insight into the unprecedented hydrodefluorination pathway.
6. Selective Mono-Defluorinative Cross-Coupling of Trifluoromethyl arenes via Multiphoton Photoredox Catalysis
Jiaqi Jia, Serik Zhumagazy, Chen Zhu, Shao-Chi Lee, Salman Alsharif, Huifeng Yue, Magnus Rueping
Chem. Eur. J. 2024, e202302927
DOI: 10.1002/chem.202302927
Abstract:
A new cross-coupling of trifluoromethyl arenes has been realized via multiphoton photoredox catalysis. Trifluoromethyl arenes were demonstrated to undergo selective mono-defluorinative alkylation under mild reaction conditions providing access to a series of valuable α,α-difluorobenzylic compounds. The reaction shows broad substrate scope and general functional group tolerance. In addition to the electron-deficient trifluoromethyl arenes that are easily reduced to the corresponding radical anion, more challenging electron-rich substrates were also successfully applied. Steady-State Stern-Volmer quenching studies indicated that the trifluoromethyl arenes were reduced by the multiphoton excited Ir-based photocatalyst.
Prashant S. Shinde, Valmik S. Shinde, Magnus Rueping
Chem. Commun., 2024, 60, 3826
DOI: 10.1039/d4cc00309h
Abstract:
The development of an electrochemical cobalt catalyzed C–Cl bond activation at room temperature for the nucleophilic addition of aryl and vinyl chlorides to α-ketoamides is described. The overall method operates through an electrochemically induced low valent cobalt catalyst that oxidatively adds to aryl or vinyl chlorides affording medicinally important 3-hydroxy oxindole and 3-hydroxypyrrolidinone scaffolds. The development of an enantioselective version using a chiral pyrox ligand is also demonstrated.
4. Excited-State Nickel-Catalyzed Amination of Aryl Bromides: Synthesis of Diphenylamines and Primary Anilines
Lidia Karpova, Matěj Daniel, Rajesh Kancherla, Krishnamoorthy Muralirajan, Bholanath Maity, Magnus Rueping
Org. Lett, 2024, 26, 1657–1661
DOI: 10.1021/acs.orglett.4c00147
Abstract:
Excited-state nickel-catalyzed C–N cross-coupling of aryl bromides with sodium azide enables the synthesis of diarylamines and primary anilines under mild reaction conditions. The oxidative addition of electron-rich aryl bromides with low-valent Ni under the photochemical conditions is endothermic. Herein, we demonstrate a light-mediated nickel-catalyzed reaction of electronically rich aryl bromides that yields diarylamines, while the reaction with electron-deficient aryl bromides gives access to anilines at room temperature. Overcoming the limitations associated with the activation of electronically rich aryl bromides in photochemical nickel catalysis, we developed a novel photoinduced Ni-catalyzed C–N cross-coupling reaction involving aryl bromides and NaN3 at room temperature. A wide range of aryl bromides, including both EDGs and EWGs, were effectively cross-coupled with sodium azide to give diarylamines and anilines in good yields. A mechanism involving the NiI/NiIII catalytic pathway in which the photoreduction of NiII to NiI is crucial for C–N cross-coupling is proposed.
3. Boosted hydrogen evolution kinetics of heteroatom-doped carbons with isolated Zn as an accelerant
Yang Li, Shouwei Zuo, Fen Wei, Cailing Chen, Guikai Zhang, Xiaojuan Zhao, Zhipeng Wu, Jing Zhang, Sibo Wang, Wei Zhou, Magnus Rueping, Yu Han, Huabin Zhang
PNAS, 2024, 121, e2315362121
DOI: 10.1073/pnas.2315362121
Abstract:
Carbon- based single- atom catalysts, a promising candidate in electrocatalysis, offer insights into electron- donating effects of metal center on adjacent atoms. Herein, we present a practical strategy to rationally design a model catalyst with a single zinc (Zn) atom coordinated with nitrogen and sulfur atoms in a multilevel carbon matrix. The Zn site exhibits an atomic interface configuration of ZnN4S1, where Zn's electron injection effect enables thermal- neutral hydrogen adsorption on neighboring atoms, pushing the activity boundaries of carbon electrocatalysts toward electrochemical hydrogen evolution to an unprecedented level. Experimental and theoretical analyses confirm the low- barrier Volmer–Tafel mechanism of proton reduction, while the multishell hollow structures facilitate the hydrogen evolution even at high current intensities. This work provides insights for understanding the actual active species during hydrogen evolution reaction and paves the way for designing high- performance electrocatalysts.
2. N-heterocyclic nitrenium charge transfer catalysis via inner-sphere electron transfer in concert with halogen-atom dissociation
Chao-Shen Zhang, Chang-Zhen Fang, Liang Yi, Chen Zhu, c Zhi-Xiang Wang, Xiang-Yu Chen and Magnus Rueping
Org. Chem. Front., 2024, 11, 673-683
DOI: 10.1039/D3QO01779F
Abstract:
Visible light photoredox-catalyzed reactions have become essential tools in organic synthesis. However, these transformations often rely on high-cost photocatalysts that require multistep synthesis and chromophore design. In recent years, charge transfer complex (CTC) photochemistry has emerged as an alternative to photoredox catalysis, but this method requires substrates to form the CTC. To overcome these limitations, we developed a new catalytic paradigm using easily available N-heterocyclic nitreniums (NHNs) as photocatalysts. Our method uses incident light absorbed by the in situ-formed CTC between NHN and its counteranion or a sacrificial donor, extending CTC photochemistry to a general catalytic mode without relying on substrates. Here, we demonstrate NHN catalysis for the photoreduction of C–Cl bonds in chloroform and activated alkyl chlorides. This approach is characterized by easily available NHNs (one-step synthesis without column purification), operational simplicity, and diverse transformations. Mechanistic studies reveal that the generated NHN aminyl radical could undergo inner-sphere single-electron transfer in concert with halogen-atom dissociation.
1. Photoexcitation of Distinct Divalent Palladium Complexes in Cross-Coupling Amination Under Air - Photoexcited State Pd(II) Catalysis
Rajesh Kancherla, Krishnamoorthy Muralirajan, Sayan Dutta, Kuntal Pal, Bo Li, Bholanath Maity, Luigi Cavallo, Magnus Rueping
Angew. Chem. Int. Ed. 2024, 63, e202314508
DOI: 10.1002/anie.202314508
ABSTRACT:
The development of metal complexes that function as both photocatalyst and cross-coupling catalyst remains a challenging research topic. So far, progress has been shown in palladium(0) excited-state transition metal catalysis for the construction of carbon-carbon bonds where the oxidative addition of alkyl/aryl halides to zero-valent palladium (Pd0) is achievable at room temperature. Distinct from Pd0-complexes that easily undergo oxidative addition with aryl/alkyl halides, the oxidative addition of aryl halides to electrophilic divalent Pd(II) is uphill and energy-demanding. Overcoming these limitations, we realized the oxidative addition of aryl halides to divalent palladium using mild photochemical conditions at room temperature under open air conditions. Various electron withdrawing and donating aryl/heteroaryl iodides were cross-coupled with sodium azide to give primary anilines by using Pd(OAc)2 as both photocatalyst and cross-coupling catalyst. We demonstrate for the first time, that divalent PdII can act as a light-absorbing species which undergoes double excitation to give the C−N cross-coupled product under air. DFT studies and mechanistic investigations support the photoexcitation of two distinct divalent palladium species and unravel the reaction mechanism.