Reduction of arenediazonium salts by tetrakis(dimethylamino)ethylene (TDAE): Efficient formation of products derived from aryl radicals

Tetrakis(dimethylamino)ethylene (TDAE 1), has been exploited for the first time as a mild reagent for the reduction of arenediazonium salts to aryl radical intermediates through a single electron transfer (SET) pathway. Cyclization of the aryl radicals produced in this way led, in appropriate substrates, to syntheses of indolines and indoles. Cascade radical cyclizations of aryl radicals derived from arenediazonium salts are also reported. The relative ease of removal of the oxidized by-products of TDAE from the reaction mixture makes the methodology synthetically attractive.

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Alcohol-Initiated Dediazoniation of Aryldiazonium Ions to Aryl Radicals: A Simple and Efficient Route to Arylboronates

Journal of Chemical Research ◽

10.3184/174751918x15362432558247 ◽

2018 ◽

Vol 42 (9) ◽

pp. 481-485

Author(s):

Xiulian Zhang ◽

Zhicheng Zhang ◽

Yongbin Xie ◽

Yujie Jiang ◽

Ruibo Xu ◽

...

Keyword(s):

Electron Transfer ◽

Bond Formation ◽

Single Electron ◽

Single Electron Transfer ◽

Aryl Radical ◽

Radical Species ◽

Aryl Radicals ◽

Efficient Access ◽

Efficient Route ◽

Operational Simplicity

A simple and efficient access to arylboronates was achieved with methanol-initiated borylation of aryldiazonium salts. Reduction of aryldiazonium ions by single electron transfer from methanol affords aryl radical species, which undergo a subsequent C–B bond formation with bis(pinacolato)diboron. This highly practical borylation process, which can be carried out on the gram-scale, enjoys operational simplicity as well as mild and catalyst-free conditions.

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Aryl radical-mediated N-heterocyclic carbene catalysis

Nature Communications ◽

10.1038/s41467-021-24144-2 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yuki Matsuki ◽

Nagisa Ohnishi ◽

Yuki Kakeno ◽

Shunsuke Takemoto ◽

Takuya Ishii ◽

...

Keyword(s):

Electron Transfer ◽

Single Electron ◽

Radical Reactions ◽

Single Electron Transfer ◽

Aryl Radical ◽

Aryl Iodide ◽

Alkyl Radicals ◽

Aryl Radicals ◽

Electron Transfer Processes ◽

Secondary Amides

AbstractThere have been significant advancements in radical reactions using organocatalysts in modern organic synthesis. Recently, NHC-catalyzed radical reactions initiated by single electron transfer processes have been actively studied. However, the reported examples have been limited to catalysis mediated by alkyl radicals. In this article, the NHC organocatalysis mediated by aryl radicals has been achieved. The enolate form of the Breslow intermediate derived from an aldehyde and thiazolium-type NHC in the presence of a base undergoes single electron transfer to an aryl iodide, providing an aryl radical. The catalytically generated aryl radical could be exploited as an arylating reagent for radical relay-type arylacylation of styrenes and as a hydrogen atom abstraction reagent for α-amino C(sp3)–H acylation of secondary amides.

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Radical Biocatalysis: Using Non-Natural Single Electron Transfer Mechanisms to Access New Enzymatic Functions

Synlett ◽

10.1055/s-0037-1611818 ◽

2019 ◽

Vol 31 (03) ◽

pp. 248-254 ◽

Cited By ~ 4

Author(s):

Todd K. Hyster

Keyword(s):

Electron Transfer ◽

Active Sites ◽

Hydrogen Atom Transfer ◽

Single Electron ◽

Great Promise ◽

Single Electron Transfer ◽

Radical Intermediates ◽

Redox Activation ◽

Transfer Mechanisms ◽

Ground State Electron

Exploiting non-natural reaction mechanisms within native enzymes is an emerging strategy for expanding the synthetic capabilities of biocatalysts. When coupled with modern protein engineering techniques, this approach holds great promise for biocatalysis to address long-standing selectivity and reactivity challenges in chemical synthesis. Controlling the stereochemical outcome of reactions involving radical intermediates, for instance, could benefit from biocatalytic solutions because these reactions are often difficult to control by using existing small molecule catalysts. General strategies for catalyzing non-natural radical reactions within enzyme active sites are, however, undeveloped. In this account, we highlight three distinct strategies developed in our group that exploit non-natural single electron transfer mechanisms to unveil previously unknown radical biocatalytic functions. These strategies allow common oxidoreductases to be used to address the enduring synthetic challenge of asymmetric hydrogen atom transfer.1 Introduction2 Photoinduced Electron Transfer from NADPH3 Ground State Electron Transfer from Flavin Hydroquinone4 Enzymatic Redox Activation in NADPH-Dependent Oxidoreductases5 Conclusion

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Intermolecular oxyarylation of olefins with aryl halides and TEMPOH catalyzed by the phenolate anion under visible light

Chemical Science ◽

10.1039/d0sc02160a ◽

2020 ◽

Vol 11 (27) ◽

pp. 6996-7002

Author(s):

Kangjiang Liang ◽

Qian Liu ◽

Lei Shen ◽

Xipan Li ◽

Delian Wei ◽

...

Keyword(s):

Electron Transfer ◽

Visible Light ◽

Aryl Halides ◽

Single Electron ◽

Single Electron Transfer ◽

Strong Reduction ◽

Aryl Radicals ◽

Reduction Potentials

The phenolate anion was developed as a new photocatalyst with strong reduction potentials (−3.16 V vs. SCE) to reduction of aryl halides to aryl radicals through single electron transfer.

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Applications of ytterbium(II) reagent as Grignard reagent and single electron transfer reagent in the synthesis of 3-substituted-2-oxindoles

Synthesis ◽

10.1055/a-1516-7917 ◽

2021 ◽

Author(s):

Pengkai Wang ◽

yan xu cao ◽

Songlin Zhang

Keyword(s):

Electron Transfer ◽

Grignard Reagent ◽

Nucleophilic Reagent ◽

Point Of View ◽

Single Electron ◽

Single Electron Transfer ◽

One Pot ◽

First Time ◽

Isatin Derivatives

The utilities of ytterbium(II) reagent, both as nucleophilic reagent and single electron transfer reagent in the reaction of isatin derivatives with ytterbium(II) reagent are reported for the first time in this paper. From a synthetic point of view, a general, efficient, and experimentally simple one-pot method for preparation of 3-substituted-2-oxindoles was developed.

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The Intermediacy of Free Aryl Radicals in the Reaction of o-Alkenyloxybenzenediazonium Salts With Ferrocene

Australian Journal of Chemistry ◽

10.1071/ch9920857 ◽

1992 ◽

Vol 45 (5) ◽

pp. 857 ◽

Cited By ~ 15

Author(s):

ALJ Beckwith ◽

RA Jackson ◽

RW Longmore

Keyword(s):

Electron Transfer ◽

Aryl Radicals ◽

Arenediazonium Salts

The formation of 3-ferrocenylmethyl-2,3-dihydrobenzofuran (5a) and similar products bearing cyclized substituents, when ferrocene or mixtures of ferrocene and ferrocenium ion are treated witho - allyloxybenzene - or o-but-3-enyloxybenzene-dimonium salts, provides unequivocal evidence for the intermediacy of free aryl radicals in the reaction of ferrocene with arenediazonium salts. The results are consistent with a mechanism involving electron transfer and dediazoniation followed by homolytic attack on ferroce nium ion.

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Reaction of Thianthrene Cation Radical with Diarylmercurials. Search for Single Electron Transfer Is Elusive

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19930082 ◽

1993 ◽

Vol 58 (1) ◽

pp. 82-88 ◽

Cited By ~ 5

Author(s):

A. K. M. M. Hoque ◽

Henry J. Shine ◽

T. Krishnan Venkatachalam

Keyword(s):

Electron Transfer ◽

Cation Radical ◽

Product Formation ◽

Single Electron ◽

Single Electron Transfer ◽

Aryl Radicals ◽

Stoichiometric Ratios

Diarylmercurials (Ar2Hg) with Ar = p-tolyl Ib, o-tolyl Ic, p-anisyl Id and 2-allyloxy-4,5-dimethylphenyl Ie, reacted with thianthrene cation radical perchlorate (Th.+ClO4-) in two stoichiometric ratios: 2 : 1 and 4 : 1 (Th.+ClO4-/Ar2Hg). In the 2 : 1 ratio the products were the 5-arylthianthreniumyl perchlorates IIb - IIe, thianthrene (Th) and ArHg+ClO4- (assayed as ArHgCl, III) in quantitative yields. In the 4 : 1 ratio reaction with ArHg+ occurred, too, and the products were IIb - IIe, Th, the complex Th3Hg(ClO4)2 and HgO (after workup). In contrast, Ph2Hg (Ia) did not react beyond the 2 : 1 stoichiometry. In the reactions with Ie, no evidence for formation and cyclization of free 2-allyloxy-4,5-dimethylphenyl radical was found. Reaction of and product formation from these arylmercurials, therefore, does not occur in single electron transfer steps that lead to free aryl radicals. Instead electron transfer appears to occur within a complex of Ar2Hg with Th.+ from which II and other products are subsequently formed.

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Diazonium Salts as Nitrogen-Based Lewis Acids

Synlett ◽

10.1055/s-0037-1612109 ◽

2019 ◽

Vol 30 (08) ◽

pp. 875-884 ◽

Cited By ~ 4

Author(s):

Evi Habraken ◽

Andrew Jupp ◽

J. Slootweg

Keyword(s):

Electron Transfer ◽

Lewis Acids ◽

Single Electron ◽

Azo Compounds ◽

Diazonium Salts ◽

Single Electron Transfer ◽

Organic Transformations ◽

Aryl Radical ◽

Lewis Bases ◽

Donor Acceptor

Aryldiazonium salts are widely used in many organic transformations with displacement of N2 or through addition to the terminal nitrogen. Such aryldiazonium salts can be viewed as N-based Lewis acids that can react with Lewis bases to synthesize a wide variety of azo compounds. Additionally, diazonium salts are known to undergo single-electron transfer and release N2, forming an aryl radical, which results in different reactivity. Herein, we provide a concise overview of the reactivity of aryldiazonium salts undergoing classical donor-acceptor reactivity or single-electron transfer.

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Aromatic substitutions of arenediazonium salts via metal catalysis, single electron transfer, and weak base mediation

Organic & Biomolecular Chemistry ◽

10.1039/c8ob00591e ◽

2018 ◽

Vol 16 (27) ◽

pp. 4942-4953 ◽

Cited By ~ 18

Author(s):

Denis Koziakov ◽

Guojiao Wu ◽

Axel Jacobi von Wangelin

Keyword(s):

Electron Transfer ◽

Single Electron ◽

Single Electron Transfer ◽

Weak Base ◽

Metal Catalysis ◽

Hazard Potential ◽

Recent Developments ◽

Arenediazonium Salts ◽

Operational Simplicity

Radical aromatic substitutions of arenediazonium salts can be initiated by various methods. The recent developments of weak base-mediated protocols provide great advantages over conventional metal-mediated or photoredox reactions by their operational simplicity, price, hazard potential and scalability.

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