Arylaminyl radicals studied by laser flash photolysis of di-tert-butyl peroxide in the presence of arylamines

Leyva, Elisa; Platz, Matthew S.; Niu, Baohua.; Wirz, Jakob

doi:10.1021/j100293a017

Cited by 46 publications

(45 citation statements)

References 2 publications

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“…As shown in the bottom half of figure 1, a hydrogen atom transfer mechanism can also explain aromatization of the dihydropyridine and radical formation. In this mechanism mechanism, hydrogen atom abstraction from nitrogen (Leyva et al 1987) the formation of an aminyl radical, which can aromatize by loss of the Cq alkyl group as a free radical. This mechanism has the attractive feature that it rationalizes the observation that two N-alkyl dihydropyridine Hantzsch esters do not inactivate P450 until their alkyl groups are first oxidatively removed (Lee et al 1988).…”

Section: Je-mentioning

confidence: 99%

On the mechanism of amine oxidations by P450

Karki

Dinnocenzo

1995

Xenobiotica

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1. Experimental data previously used to support an electron/proton transfer mechanism for oxidative dealkylation of amines by P450 are critically analysed with the conclusion that the mechanistic evidence is indecisive. 2. A new mechanistic criterion recently proposed to distinguish between electron/proton transfer and hydrogen atom transfer mechanisms is discussed. It is based on isotope effect profiles determined for the deprotonation of a series of para-substituted N-methyl-N-trideuteriomethyl)aniline cation radicals by pyridine and for hydrogen atom abstraction from the corresponding neutral amines by the tert-butoxyl radical. These reactions model the steps proposed in the two P450 mechanisms. 3. Isotope effect profiles measured for the demethylation of substituted NN-bis(dideuteriomethyl)anilines by four different forms of P450 were found to be experimentally indistinguishable from the hydrogen atom transfer profile, and distinctly different from the cation radical deprotonation profile. This provides strong evidence that P450 oxidatively dealkylates the amines by a hydrogen atom transfer mechanism and not by an electron/proton transfer mechanism.

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Section: Je-mentioning

confidence: 99%

On the mechanism of amine oxidations by P450

Karki

Dinnocenzo

1995

Xenobiotica

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“…An absorption band, which matches the literature value for the diphenylamine radical cation, appears immediately after the laser pulse at 680 nm (18). The signal at 680 nm decays within 2 μs, and a new signal corresponding to the literature value for the neutral diphenylamine radical appears at 710 nm (19). A new signal is also seen at 450 nm 1.5 μs after the laser pulse.…”

Section: Resultsmentioning

confidence: 55%

Photochemistry and Phototoxicity of Aloe Emodin¶

Vath

Wamer

Falvey

2002

Photochemistry and Photobiology

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Photochemical pathways leading to the phototoxicity of the aloe vera constituent aloe emodin were studied. The results indicate a photochemical mechanism involving singlet oxygen to be the most likely pathway responsible for the observed phototoxicity. Aloe emodin was found to efficiently generate singlet oxygen when irradiated with UV light (ΦΔ= 0.56 in acetonitrile). The survival of human skin fibroblast cells in the presence of aloe emodin was found to decrease upon irradiation with UV light. A further decrease in cell survival was observed in D2O compared with H2O, suggesting the involvement of singlet oxygen as the primary pathway. Laser flash photolysis experiments were also carried out on aloe emodin alone and in the presence of various biological substrates. Aloe emodin proved to be relatively photostable (Φ= 1 × 10−4) and a poor photo‐oxidant (E*red=+1.02 V). Only absorption bands caused by the triplet state of aloe emodin (λmax= 480 nm) and the aloe emodin conjugate base (λmax= 520 nm) were observed in the transient spectra.

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“…The importance of alkoxyl radicals in organic, biological, and atmospheric chemistry has motivated numerous studies on their reactions. Most of these studies have been carried out employing tert-butoxyl radicals and have shown that these radicals rapidly abstract hydrogen from different substrates, such as hydrocarbons [l-51, ethers [6], alcohols [2,7], sulfides [8], and alkylamines [9-111 to give carbon-centered radicals and from phenols [12], silanes [13], and aryl amines [14] to give the corresponding heteroatom centered radicals. In general, the rate of the process has been interpreted in terms of the strength of the broken bond and the contribution of charge transfer configurations to the critical energies.…”

Section: Introductionmentioning

confidence: 99%

“…Among the families of compounds bearing reactive hydrogen atoms and aromatic conjugated double bonds stand the indole derivatives. For indole, it has been reported that tert-butoxyl radicals abstract the hydrogen atom from the nitrogen giving the indolyl radical [14]. However, other radicals react in a different and more complex way.…”

Section: Introductionmentioning

confidence: 99%

ChemInform Abstract: Reactivity of tert.‐Butoxyl Radicals Towards Substituted Indole Derivatives

et al. 1991

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Tert-butoxyl radicals react with indole and methyl substituted derivatives by hydrogen abstraction. For those compounds which are unsubstituted at the N-atom, hydrogen abstraction takes place almost exclusively at the N-H bond. The reactivity of these compounds correlates with their donor electron capacity, pointing to significant contribution of charge transfer to the transition state stability. Substitution at the N atom considerably decreases the reactivity.

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Arylaminyl radicals studied by laser flash photolysis of di-tert-butyl peroxide in the presence of arylamines

Cited by 46 publications

References 2 publications

On the mechanism of amine oxidations by P450

On the mechanism of amine oxidations by P450

Photochemistry and Phototoxicity of Aloe Emodin¶

ChemInform Abstract: Reactivity of tert.‐Butoxyl Radicals Towards Substituted Indole Derivatives

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