Implementing Hydrogen Atom Transfer (HAT) Catalysis for Rapid and Selective Reductive Photoredox Transformations in Continuous Flow

Steiner, Alexander; Williams, Jason D.; Rincón, Juan A.; Frutos, Óscar de; Mateos, Carlos; Kappe, C. Oliver

doi:10.1002/ejoc.201900952

Cited by 22 publications

(17 citation statements)

References 49 publications

(29 reference statements)

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“…The optical properties of the polymers were studied via UV/vis spectroscopy in water as well as organic solvent (i.e., acetonitrile; see Figure S5 in the Supporting Information). The UV/Vis spectra show in both solvents the typical absorption bands of the incorporated PTH catalyst with maxima at around 258 and 320 nm, indicating the successful incorporation of the photocatalyst within the polymer scaffold (in accordance with NMR spectroscopy, see Figures S6–S8 in the Supporting Information).…”

Section: Resultssupporting

confidence: 76%

Amphiphilic Polymeric Nanoparticles for Photoredox Catalysis in Water

Eisenreich

Meijer

Palmans

2020

Chemistry A European J

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Photoredox catalysis has recently emerged as a powerful synthesis tool in organic and polymer chemistry. In contrast to the great achievements realized in organic solvents, performing photocatalytic processes efficiently in aqueous media encounters several challenges. Here, it is presented how amphiphilic single‐chain polymeric nanoparticles (SCPNs) can be utilized as small reactors to conduct light‐driven chemical reactions in water. By incorporating a phenothiazine (PTH) catalyst into the polymeric scaffold, metal‐free reduction and C−C cross‐coupling reactions can be carried out upon exposure to UV light under ambient conditions. The versatility of this approach is underlined by a large substrate scope, tolerance towards oxygen, and excellent recyclability. This approach thereby contributes to a sustainable and green way of implementing photoredox catalysis.

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Section: Resultssupporting

confidence: 76%

Amphiphilic Polymeric Nanoparticles for Photoredox Catalysis in Water

Eisenreich

Meijer

Palmans

2020

Chemistry A European J

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“…In the literature, there are a number of examples on light-induced hydrodehalogenation of aryl halides. 14 , 34 Here, by simply removing B 2 Pin 2 from the reaction conditions, the reductive dehalogenation of aryl halides occurred smoothly with good to excellent yields ( Table 8 ). A panel of functional groups such as ester, ketone, cyano, amide and alcohol were tolerated.…”

Section: Resultsmentioning

confidence: 96%

Luminescent tungsten(vi) complexes as photocatalysts for light-driven C–C and C–B bond formation reactions

Tong

et al. 2020

Chem. Sci.

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“…Finally, the optical properties of the nanoparticles were studied with UV/Vis spectroscopy with water as solvent ( Figure S10 in the Supplementary Information ). It was previously reported that the PTH absorption maxima are located around 258 and 320 nm [ 43 ], whereas ACR absorption maxima occur at 360 and 520 nm [ 16 ]. Both the polymer bound ACR and PTH moiety show absorption bands identical to those reported in the literature for the free catalysts.…”

Section: Methodology and Resultsmentioning

confidence: 99%

Photoredox-Catalyzed Reduction of Halogenated Arenes in Water by Amphiphilic Polymeric Nanoparticles

et al. 2021

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The use of organic photoredox catalysts provides new ways to perform metal-free reactions controlled by light. While these reactions are usually performed in organic media, the application of these catalysts at ambient temperatures in aqueous media is of considerable interest. We here compare the activity of two established organic photoredox catalysts, one based on 10-phenylphenothiazine (PTH) and one based on an acridinium dye (ACR), in the light-activated dehalogenation of aromatic halides in pure water. Both PTH and ACR were covalently attached to amphiphilic polymers that are designed to form polymeric nanoparticles with hydrodynamic diameter DH ranging between 5 and 11 nm in aqueous solution. Due to the hydrophobic side groups that furnish the interior of these nanoparticles after hydrophobic collapse, water-insoluble reagents can gather within the nanoparticles at high local catalyst and substrate concentrations. We evaluated six different amphiphilic polymeric nanoparticles to assess the effect of polymer length, catalyst loading and nature of the catalyst (PTH or ACR) in the dechlorination of a range of aromatic chlorides. In addition, we investigate the selectivity of both catalysts for reducing different types of aryl-halogen bonds present in one molecule, as well as the activity of the catalysts for C-C cross-coupling reactions. We find that all polymer-based catalysts show high activity for the reduction of electron-poor aromatic compounds. For electron-rich compounds, the ACR-based catalyst is more effective than PTH. In the selective dehalogenation reactions, the order of bond stability is C-Cl > C-Br > C-I irrespective of the catalyst applied. All in all, both water-compatible systems show good activity in water, with ACR-based catalysts being slightly more efficient for more resilient substrates.

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Implementing Hydrogen Atom Transfer (HAT) Catalysis for Rapid and Selective Reductive Photoredox Transformations in Continuous Flow

Cited by 22 publications

References 49 publications

Amphiphilic Polymeric Nanoparticles for Photoredox Catalysis in Water

Amphiphilic Polymeric Nanoparticles for Photoredox Catalysis in Water

Luminescent tungsten(vi) complexes as photocatalysts for light-driven C–C and C–B bond formation reactions

Photoredox-Catalyzed Reduction of Halogenated Arenes in Water by Amphiphilic Polymeric Nanoparticles

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