Nitroxide Radicals: Properties, Synthesis and Applications

Karoui, Hakim; Moigne, F. Le; Ouari, Olivier; Tordo, Paul

doi:10.1002/9780470666975.ch5

Cited by 71 publications

(58 citation statements)

References 313 publications

(143 reference statements)

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“…[25] Common route to nitroxides is oxidation of secondary amines. [26,27] However, in case of diarylamines, delocalization of the nitrogen lone electron pair over ortho-and para-positions of the phenyl rings is observed. This provokes an additional oxidation route via attack of the oxidant at the vacant para-position yielding by-products of quinoid type.…”

Section: Introductionmentioning

confidence: 99%

Competitive Routes for Electrochemical Oxidation of Substituted Diarylamines: the Guidelines

et al. 2018

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Electrochemical oxidation of diphenylamines with electron‐donating and electron‐withdrawing substituents in various combinations was investigated. It was shown that the subsequent reaction channels for the radical cations are dependent on the location and electronic properties of the substituents in both phenyl rings. Guidelines for the prediction of the dominant reaction path were formulated. The conclusions developed will be useful for planning electrosynthesis. Digital simulation of the voltammograms allowed estimating the mechanism of N,N‐diaryl‐5,10‐dihydrophenazine formation (which is one of the main reaction channels); the corresponding radical cations were isolated for the first time and characterized by X‐ray, electrochemical and spectral methods. Oxidation peak potentials for diarylaminyl anions (obtained using electrochemically generated base) were measured providing information for mechanistic estimation of anti/prooxidant activity of diarylamines in radical processes.

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Section: Introductionmentioning

confidence: 99%

Competitive Routes for Electrochemical Oxidation of Substituted Diarylamines: the Guidelines

et al. 2018

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“…[4] Diarylnitroxides can be obtained through the oxidation of diarylamines by using H 2 O 2 /Na 2 WO 4 or m-chloroperbenzoic acid. [5,6] At present, only af ew stable diarylnitroxides are known,a nd all of them are para-substituted derivatives to prevent further chemical transformations of the radicals that are possible due to spin delocalizationo ver the phenylr ings. This substantially limits the scopeo fs table radicals available.A na lternative route to the stabilization of the radicalm ight be insertion of ab ulky substituent into the ortho position, which will force the aryl ring to twist away from the NÀOp lane;t hus disturbing its conjugation to the radicalcenter.…”

Section: Introductionmentioning

confidence: 99%

Copper‐Assisted Amination of Boronic Acids for Synthesis of Bulky Diarylamines: Experimental and DFT Study

Levitskiy

Grishin

Sentyurin

et al. 2017

Chemistry A European J

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Comparative investigation of copper-assisted oxidative and reductive amination showed that the latter was preferable for the synthesis of bulky diarylamines. DFT estimation of the mechanism of copper(I)-assisted reductive amination of boronic acids with aryl nitroso compounds was performed and possible active species were identified. DFT estimation of the steric penalty revealed that the barrier for the transmetalation step for the hindered nitroso compound was almost the same as that for the unsubstituted one, whereas a bulky group in the boronic acid increased the activation energy. A DFT study of the influence of the electronic properties of the substituents in both reactants on the activation energy revealed that the optimal combination for the synthesis of unsymmetrical diarylamines to provide better yields was an electron-rich aryl boronic acid and an electron-deficient nitroso compound. By using these helpful guidelines, a series of new bulky diarylamines were obtained and fully characterized.

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“…Chemistry and applications of TEMPO and other nitroxide radicals have been reviewed in several monographs [3][4][5]. Important are applications connected with electron capture or transfer.…”

Section: Introductionmentioning

confidence: 99%

The electronic structure of TEMPO, its cation and anion

et al. 2013

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The electronic structure of TEMPO (2,2,6,6-Tetramethylpiperidine-N-oxyl) and its cation and anion were studied experimentally using the electron spectroscopy techniques, dissociative electron attachment (DEA) spectroscopy, electron energy-loss spectroscopy, measurement of elastic and vibrational excitation (VE) cross sections and HeI photoelectron spectroscopy. The experiments were supplemented by quantum-chemical calculations of excitation energies, ionisation potential and the Franck-Condon profile of the first photoelectron band. Electron energy-loss spectra were recorded up to 12 eV and revealed a number of bands that were assigned to two valence and a number of Rydberg transitions. VE cross sections reveal a broad band in the 3-12 eV range, assigned to σ * shape resonances and signals in the 0-1 eV range, assigned to a shape resonance corresponding to a temporary capture of the incident electron in the (already singly occupied) π * orbital. Narrow threshold peaks in the VE cross sections are assigned to dipole-bound resonances. The major DEA fragment was found to be O − , with bands at 5.0 and 6.87 eV, assigned to core excited resonances.

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Nitroxide Radicals: Properties, Synthesis and Applications

Cited by 71 publications

References 313 publications

Competitive Routes for Electrochemical Oxidation of Substituted Diarylamines: the Guidelines

Competitive Routes for Electrochemical Oxidation of Substituted Diarylamines: the Guidelines

Copper‐Assisted Amination of Boronic Acids for Synthesis of Bulky Diarylamines: Experimental and DFT Study

The electronic structure of TEMPO, its cation and anion

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