- The Reaction of the CCl3O2 Radical with Indoles
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In its reaction with indoles the CCl3O2 radical adds predominantly to the C(2)-C(3) double bond.Only a minor fraction accounts for one-electron oxidation.The 3-adduct undergoes rapid cleavage along the peroxidic bond while several rearrangement paths are
- Shen, Xinhua,Lind, Johan,Eriksen, Trygve E.,Merenyi, Gabor
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- The Reaction of Indoles in Aqueous Solution Initiated by One-electron Oxidation
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By pulse or gamma radiolysis in the presence of Br-, 1-methylindole (1b) is oxidized to its radical cation (2b), which adds to (1b) to form a radical dimer (8b).Species (2b) also reacts with OH- to yield the pseudo-base, proposed to be the C2-OH adduct (4b).Identical end-product yields and spectral comparison reveal that the addition of OH. radicals to (1b) also produces (2b) and (4b) but virtually no other OH. adducts to (1b).The selectivity of OH towards the C2 position appears to apply to the other indoles as well.The neutral indolyl radicals (3) disappear both by coupling and dismutation.Discrimination between these modes is governed by the substituent.A methyl group at the C3 position favours C3-C3' coupling.Molecular oxygen adds to neutral indolyl radicals at the C3 position.The measured and estimated rates of O2 addition relate to the redox potentials of the indolyl radicals.The reaction between O2-. and the indolyl radical cation (2) produces (1) and O2.On the other hand, O2-. couples to (3) to yield C3-OOH hydroperoxides (14).The latter decompose into C2-C3 opened amides (13) with concomitant chemiluminescence.
- Shen, Xinhua,Lind, Johan,Eriksen, Trygve E.,Merenyi, Gabor
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p. 597 - 603
(2007/10/02)
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- Dioxygen Transfer from 4a-Hydroperoxyflavin Anion. 3. Oxygen Transfer to the 3-Position of Substituted Indoles
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The 4a-hydroperoxyflavin anion (4a-FlEtO2(-)) spontaneously decays with a rate constant of 4.2E-2 s-1 (tert-butyl alcohol, 30 deg C).In the presence of the anions of 2,3-dimethylindole (1a-) and 5-methoxy-3-methyl-2-phenylindole (2a-) the pseudo-first-order rate constant (Kobsd) for disappearance of 4a-FlEtO2(-) increase.Plots of 1/kobsd vs. 1/-> and 1/-> are linear, and the limiting rate constants for 4a-FlEtO2(-) disappearance at high values of -> and -> were calculated, from the intercepts, to be 0.33 and 0.37 s-1, respectively.In a previous study the limiting rate constants were 0.36 and 0.37 s-1 when the anions of 2,6-di-tert-butyl-4-methylphenol and 3,5-di-tert-butylcatechol were employed.This limiting rate constant of 0.36 s-1 is assigned as the forward rate for the conversion of 4a-FlEtO2(-) (in an endothermic equilibrium) to a species (X) which, on being trapped by substrate anion, transfers a peroxy moiety to the trapping agent.The yields of the dioxygen-transfer products formed from 1a- and 2a- are 24percent and 41percent, respectively.The singlet oxygen-trapping agents, 2,5-dimethylfuran and tetramethylethylene, do not increase the rate of disappearance of 4a-FlEtO2(-) and, therefore, do not trap X.Species X cannot be solvent separated 1O2 and FlEt(-).Moreover, the rate constants for reaction of triplet oxygen with 1a- and 2a- are 1E3 - 1E4 too small for X to be solvent separated 3O2 and FlEt(-).The possibility of X being solvent separated FlEt* and O2(-*) is considered.Possible identities for X include a complex of an oxygen and a flavin species and a 4a,10a-dioxetane of reduced flavin.
- Muto, Shigeaki,Bruice, Thomas C.
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p. 7559 - 7564
(2007/10/02)
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