Recent advances in the chemistry of ketyl radicals

Péter, A.; Agasti, Soumitra; Knowles, Oliver; Pye, Emma; Procter, David J.

doi:10.1039/d0cs00358a

Cited by 106 publications

(91 citation statements)

References 58 publications

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“…We demonstrated for the first time that the generation of ketyl radical anion via disulfide radical anion can be achieved. It is worth mentioning that: (i) SET reduction of ketones is a classical approach for the formation of ketyl radical anions, and such an approach has been used extensively in organic synthesis, as documented by the recently published tutorial review [ 32 ]; and (ii) ketyl radical anions formation have been typically carried out by means of dissolving metals such as Li, Na, and K, usually in liquid ammonia solution and in the presence of a proton source [ 33 ]. It can be envisaged that our bioinspired work will foster applications for SET methodology in aqueous environment.…”

Section: Resultsmentioning

confidence: 99%

Biomimetic Ketone Reduction by Disulfide Radical Anion

et al. 2021

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The conversion of ribonucleosides to 2′-deoxyribonucleosides is catalyzed by ribonucleoside reductase enzymes in nature. One of the key steps in this complex radical mechanism is the reduction of the 3′-ketodeoxynucleotide by a pair of cysteine residues, providing the electrons via a disulfide radical anion (RSSR•−) in the active site of the enzyme. In the present study, the bioinspired conversion of ketones to corresponding alcohols was achieved by the intermediacy of disulfide radical anion of cysteine (CysSSCys)•− in water. High concentration of cysteine and pH 10.6 are necessary for high-yielding reactions. The photoinitiated radical chain reaction includes the one-electron reduction of carbonyl moiety by disulfide radical anion, protonation of the resulting ketyl radical anion by water, and H-atom abstraction from CysSH. The (CysSSCys)•− transient species generated by ionizing radiation in aqueous solutions allowed the measurement of kinetic data with ketones by pulse radiolysis. By measuring the rate of the decay of (CysSSCys)•−at λmax = 420 nm at various concentrations of ketones, we found the rate constants of three cyclic ketones to be in the range of 104–105 M−1s−1 at ~22 °C.

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Section: Resultsmentioning

confidence: 99%

Biomimetic Ketone Reduction by Disulfide Radical Anion

et al. 2021

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“…(Fe(II)À O 1.8565(10) Å) [9] and in the general range found for anionic Odonor ligands. The iron benzophenone imine complex [3] À exhibits an FeÀ N bpi bond length of 1.917(2) Å with N bpi À C distance of 1.299(3) Å. For [4] À both the CoÀ N bpi (1.946(2) Å) and the N bpi À C bonds are longer (1.350(4) Å) (Table 1).…”

Section: Synthesis and Structurementioning

confidence: 99%

“…While the value of N bpi À C of [4] À is comparable to cobalt(II) complexes of monoreduced aryliminopyridines (approx. 1.34 Å), [26] the N bpi À C distance of the iron complex [3] À is surprisingly short. [27] However, the very short FeÀ N bpi bond implicated an anionic amide ligand which gave overall an ambiguous picture for [3] À on a structural level.…”

Section: Synthesis and Structurementioning

confidence: 99%

“…In recent years, the importance of these and other radical anions further emerged due to their role as crucial intermediates in photoredox catalysis. [3,5] Hitherto, experimental insights into those radical anions is essentially restricted to in situ EPR-and UV/Vis spectroscopic data. [6] Another way to expand the knowledge of these radical anions is by isolation of their metal complexes.…”

Section: Introductionmentioning

confidence: 99%

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Cobalt and Iron Stabilized Ketyl, Ketiminyl and Aldiminyl Radical Anions

Sieg

Pessemesse

Reith

et al. 2021

Chemistry A European J

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Carbonyl and iminyl based radical anions are reactive intermediates in a variety of transformations in organic synthesis. Herein, the isolation of ketyl, and more importantly unprecedented ketiminyl and aldiminyl radical anions coordinated to cobalt and iron complexes is presented. Insights into the electronic structure of these unusual metal bound radical anions is provided by X-Ray diffraction analysis, NMR, IR, UV/Vis and Mössbauer spectroscopy, solid and solution state magnetometry, as well as a by a detailed computational analysis. The metal bound radical anions are very reactive and facilitate the activation of intra-and intermolecular CÀ H bonds.

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“…Ketyl radical anion and ketyl radicals are highly versatile reactive intermediates, well known for their synthetic utility to forge C−C bonds accessing the functionalized products from carbonyl substrates [63a] . In this context, the synthesis of bis‐oxindoles 115 via photoredox catalyzed reductive dimerization of isatins 107 was accomplished by Xiang and co‐workers in 2017 (Scheme 42).…”

Section: From Isatins and 3‐ylideneoxindolesmentioning

confidence: 99%

Visible Light Mediated Synthesis of Oxindoles

Singh

Sharma

2021

Adv Synth Catal

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Functionalized oxindoles are privileged heterocyclic scaffolds and common core structural motifs that are broadly present in numerous natural products and serve as key intermediates in the synthesis of biological products, agrochemicals, and pharmaceuticals. Oxindoles exhibit a broad pharmacological and physiological activities, and diverse range of applications in medicinal chemistry and biomedical research. Owing to these fascinating biological and physiological activities of oxindoles, several methodologies have been developed for the construction of oxindoles. In the past decade, the visible light mediated methodologies have attracted substantial attention and emerged as a promising approach for the construction of oxindoles. In this review, the visible light mediated synthesis of oxindoles have been described.

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Recent advances in the chemistry of ketyl radicals

Abstract: Ketyl radicals are valuable reactive intermediates for synthesis. This review highlights exciting recent developments in the chemistry of ketyl radicals by comparing contemporary and more classical approaches for their generation and use.

Cited by 106 publications

References 58 publications

Biomimetic Ketone Reduction by Disulfide Radical Anion

Biomimetic Ketone Reduction by Disulfide Radical Anion

Cobalt and Iron Stabilized Ketyl, Ketiminyl and Aldiminyl Radical Anions

Visible Light Mediated Synthesis of Oxindoles

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