Mechanistic investigation of xanthene oxidation by heterogeneous and homogeneous electron transfers

Salah, Nasr Ben; M'Halla, F.

doi:10.1016/s0022-0728(00)00091-7

Cited by 15 publications

(14 citation statements)

References 34 publications

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“…Application of homogeneous redox catalysis to a-phellandrene and c-terpinene oxidation allowed the determination of the corresponding cation radical deprotonation rates. The values obtained are in the same range as those determined in previous studies [18,19]. Nevertheless, we notice that the deprotonation rate constant of c-terpinene cation radical has a slightly higher value due to more localization of the positive charge in this intermediate.…”

Section: Resultssupporting

confidence: 86%

Electrochemical study of the anodic oxidation of terpinenes at the electrode and by homogeneous redox catalysis

Salah

Matoussi

2005

Journal of Electroanalytical Chemistry

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Section: Resultssupporting

confidence: 86%

Electrochemical study of the anodic oxidation of terpinenes at the electrode and by homogeneous redox catalysis

Salah

Matoussi

2005

Journal of Electroanalytical Chemistry

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“…However, as an alternative, the reaction could proceed through a hydride‐transfer step from the dihydroheteroanthracenes to chloranil, followed by conjugate addition of the sulfonamide to the cationic heteroanthracenium derivative. The two‐electron oxidation and deprotonation of xanthene, thioxanthene and N ‐methyldihydroacridine has previously been studied by electrochemical or combined radiolytic and photochemical oxidation and hydride transfer to triphenylmethyl perchlorate (Scheme a,b) …”

Section: Resultsmentioning

confidence: 99%

Uncatalyzed Oxidative C−H Amination of 9,10‐Dihydro‐9‐Heteroanthracenes: A Mechanistic Study

Leest

grooten

Vlugt

et al. 2019

Chemistry A European J

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A new method for the one‐step C−H amination of xanthene and thioxanthene with sulfonamides is reported, without the need for any metal catalyst. A benzoquinone was employed as a hydride (or two‐electron and one‐proton) acceptor. Moreover, a previously unknown and uncatalyzed reaction between iminoiodanes and xanthene, thioxanthene and dihydroacridines (9,10‐dihydro‐9‐heteroanthracenes or dihydroheteroanthracenes) is disclosed. The reactions proceed through hydride transfer from the heteroarene substrate to the iminoiodane or benzoquinone, followed by conjugate addition of the sulfonamide to the oxidized heteroaromatic compounds. These findings may have important mechanistic implications for metal‐catalyzed C−H amination processes involving nitrene transfer from iminoiodanes to dihydroheteroanthracenes. Due to the weak C−H bond, xanthene is an often‐employed substrate in mechanistic studies of C−H amination reactions, which are generally proposed to proceed via metal‐catalyzed nitrene insertion, especially for reactions involving nitrene or imido complexes that are less reactive (i.e., less strongly oxidizing). However, these substrates clearly undergo non‐catalyzed (proton‐coupled) redox coupling with amines, thus providing alternative pathways to the widely assumed metal‐catalyzed pathways.

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“…During the anodic scan over a potential range 0.0 to 2.5 V (or 3.0 V), 1a (0.01 ), pyrrolidine (0.01 ), and 2a (0.01 ) showed an oxidation peak at 2.7, 1.4, and 2.0 V, respectively versus a silver-wire pseudoreference electrode at a scan rate of 0.1 Vs -1 (Figure 1, a). [4,9] An oxidation peak for a mixture of compound 1a (0.01 ) and pyrrolidine (0.005 ) was observed at 0.8 V, which was confirmed to be the oxidation peak potential corresponding to the enamine formed from 1a and pyrrolidine (Figure 1, b). [4] In the cyclic voltammetry of a mixture of 1a (0.01 ), pyrrolidine (0.005 ), and 2a (0.02 ), three oxidation waves appeared at E p,a = 0.8, 2.3, and 2.9 V, respectively, which corresponded to the oxidation of in situ formed enamines 1b and 1a.…”

Section: Resultsmentioning

confidence: 69%

Electro‐Organocatalysis: Enantioselective α‐Alkylation of Aldehydes

Mho

Kang

et al. 2010

Eur J Org Chem

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The asymmetric organocatalyzed α‐alkylation of aldehydes via a cationic radical enamine intermediate was performed under environmentally benign electro‐oxidation conditions without the use of chemical oxidants. To promote the desired α‐alkylation reaction of aldehydes, various aldehydes with xanthene or cycloheptatriene groups were exposed to electro‐organocatalytic conditions to afford optically active α‐substituted aldehydes (α‐alkylated aldehydes) in good yield. A reaction mechanism involving the cationic radical enamine was proposed based on the cyclic voltammetry (CV) results, DFT calculations, and control experiments.

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Mechanistic investigation of xanthene oxidation by heterogeneous and homogeneous electron transfers

Cited by 15 publications

References 34 publications

Electrochemical study of the anodic oxidation of terpinenes at the electrode and by homogeneous redox catalysis

Electrochemical study of the anodic oxidation of terpinenes at the electrode and by homogeneous redox catalysis

Uncatalyzed Oxidative C−H Amination of 9,10‐Dihydro‐9‐Heteroanthracenes: A Mechanistic Study

Electro‐Organocatalysis: Enantioselective α‐Alkylation of Aldehydes

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