Farbselektive Photokatalyse: kontrollierte Bindungsaktivierung durch Redoxpotentialregulation über die Anregungslichtfarbe

Ghosh, Indrajit; König, Burkhard

doi:10.1002/ange.201602349

Cited by 96 publications

(7 citation statements)

References 32 publications

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“…Recently, König and co‐workers reported on Rhodamine 6G (Rh‐6G) as a visible light photoredox catalyst with a high reduction potential . In continuation of their interest in photocatalyzed C−H heteroarylation, these authors applyed the Rhodamine 6G catalytic system for the photocatalytic generation of heteroaryl radicals from commercially available and bench‐stable brominated substrates using DIPEA as a sacrificial electron donor under blue light (λ Ex =455 nm) irradiation at room temperature (25 °C).…”

Section: C(sp2)−h Bond Functionalizationmentioning

confidence: 99%

Visible Light‐Induced C−H Bond Functionalization: A Critical Review

et al. 2018

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In recent years,v isible-light-induced C À H bond functionalization has become an emerging field at the forefront of organic chemistry.I nag eneral sense,t hese approaches rely on the capability of metal complexes ando rganic dyes to convert visible light into chemical energy by engaging in single-electron transfer with organic substrates,t husg enerating reactivei ntermediates.T hisr eview covers most of the strategies involving visible light-induced benzylic and non-benzylic

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Section: C(sp2)−h Bond Functionalizationmentioning

confidence: 99%

Visible Light‐Induced C−H Bond Functionalization: A Critical Review

et al. 2018

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“…We compared exclusive photoexcitation of the catalyst, using a single modern narrow-band light source, with photoexcitation of both the photoredox catalyst and the visible-light-absorbing metastable intermediates using two different narrow-band light sources. While photoexcitation of intermediate species has most certainly, albeit inadvertently, occurred since the beginnings of photochemistry, only recently has it been discussed in photoredox catalysis, − and it has not been proposed as a method to reduce catalyst inactivation. To the best of our knowledge, light-absorbing photoredox intermediates from broadly used organic photocatalysts, such as eosin, have not been intentionally and separately photoexcited to improve regeneration in organic or macromolecular synthesis.…”

Section: Introductionmentioning

confidence: 99%

Excitation of Metastable Intermediates in Organic Photoredox Catalysis: Z-Scheme Approach Decreases Catalyst Inactivation

et al. 2018

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Despite the numerous applications of eosin Y as an organic photoredox catalyst, substantial mechanistic aspects of the photoredox process have remained elusive. Through deductive, steady-state kinetic studies, we first propose a mechanism for alkaline, aqueous photoredox catalysis using eosin Y, triethanolamine, and oxygen, integrating photo- and nonphotochemical steps. The photoredox cycle begins with a single-electron transfer (SET) induced when eosin Y absorbs green light. This photoinduced SET leads to the formation of a metastable radical trianion that can be fully reduced to inactivated leuco eosin Y via H+/e–/H+ transfer or regenerated to eosin Y via ground-state SET to oxygen. Since the radical trianion absorbs violet light, we tested the effect of radical trianion photoexcitation on catalyst regeneration. We found that excitation of the metastable radical trianion in the presence of a threshold concentration of oxygen enabled ∼100% regeneration of eosin Y. The response to violet light supports the important role of the metastable radical trianion and indicates that the photoredox cycle can be closed via a secondary photoinduced SET event. The idea of photoredox cycles with two consecutive photoinduced electron transfer (PET) steps is not intuitive and is introduced as a tool to increase photocatalyst turnover by selectively favoring regeneration over “death”. This alludes to the Z-scheme in biological photosynthesis, where multiple PET reactions, often triggered by different frequencies, promote highly selective biochemical transformations by precluding unproductive SET events in plants and bacteria. We expect that the simple Z-scheme model introduced here will enable more efficient use of organic photoredox catalysts in organic and materials chemistry.

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“…The fluorescence intensity of Rh‐6G was evidently quenched with the gradual addition of 1 a (Figure S1). This fluorescence quenching could be attributed to the generation of the radical anion of Rh‐6G ([Rh‐6G] .− ) via photoinduced electrontransfer . Next, a series of control experiments were conducted to probe the mechanism of this transformation (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Visible Light‐Induced Aerobic Oxidative −H Arylation of Glycine Derivatives

Yang

Wang

et al. 2018

Adv Synth Catal

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A direct aerobic oxidative dehydrogenative coupling reaction of glycine derivatives with electron-rich arenes has been accomplished via the synergistic combination of organic-dye mediated photoredox catalysis and Lewis acid catalysis. This process exhibits good tolerance of functional groups and provides rapid synthesis of arylglycine derivatives at room temperature under an air atmosphere. Moreover, this protocol could be performed on a 10 mmol scale, without obvious reduction of the yield.

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Farbselektive Photokatalyse: kontrollierte Bindungsaktivierung durch Redoxpotentialregulation über die Anregungslichtfarbe

Cited by 96 publications

References 32 publications

Visible Light‐Induced C−H Bond Functionalization: A Critical Review

Visible Light‐Induced C−H Bond Functionalization: A Critical Review

Excitation of Metastable Intermediates in Organic Photoredox Catalysis: Z-Scheme Approach Decreases Catalyst Inactivation

Visible Light‐Induced Aerobic Oxidative −H Arylation of Glycine Derivatives

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