Salen complexes with bulky substituents as useful tools for biomimetic phenol oxidation research

Haikarainen, Anssi; Sipilä, Jussi; Pietikäinen, Pirjo; Pajunen, A.; Mutikainen, Ilpo

doi:10.1016/s0968-0896(01)00053-0

Cited by 37 publications

(24 citation statements)

References 45 publications

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“…Herein, we report the reactivity of 1 and 2 towards a variety of alcohols and activated alkanes, including xanthene. 10,[16][17][18][19][20][21][22][23][24] The latter substrate is significant, because its reactivity confirms that these oxidations can proceed via a concerted proton coupled electron transfer (CPET) step, as was previously surmised. 14 To test the role of the Lewis acid in activating the TEMPO moiety, we also explored the reactivity of TEMPO with FeBr 3 in Et 2 O.…”

Section: Introductionmentioning

confidence: 90%

Oxidation of Alcohols and Activated Alkanes with Lewis Acid-Activated TEMPO

et al. 2014

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The reactivity of MCl 3 (η 1 -TEMPO) (M = Fe, 1; Al, 2; TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) with a variety of alcohols, including 3,4-dimethoxybenzyl alcohol, 1phenyl-2-phenoxyethanol, and 1,2-diphenyl-2-methoxyethanol, was investigated using NMR spectroscopy and mass spectrometry. Complex 1 was effective in cleanly converting these substrates to the corresponding aldehyde or ketone. Complex 2 was also able to oxidize these substrates; however, in a few instances the products of overoxidation were also observed. Oxidation of activated alkanes, such as xanthene, by 1 or 2 suggests that the reactions proceed via an initial 1-electron concerted proton−electron transfer (CPET) event. Finally, reaction of TEMPO with FeBr 3 in Et 2 O results in the formation of a mixture of FeBr 3 (η 1 -TEMPOH) ( 23) and [FeBr 2 (η 1 -TEMPOH)] 2 (μ-O) (24), via oxidation of the solvent, Et 2 O.

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Section: Introductionmentioning

confidence: 90%

Oxidation of Alcohols and Activated Alkanes with Lewis Acid-Activated TEMPO

et al. 2014

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“…There is only one example with such stoichiometry reported so far for the compound with imidazole as a neutral N-donor ligand. 31 The positive charge is compensated with the PF 6 -anion, similar to the ionic compound with 4-aminopyridine [Mn(4-apy) 2 (sal)]PF 6 , 2, presented here.…”

Section: Resultsmentioning

confidence: 62%

Two new mononuclear manganese(III) salen complexes

Grabner

Bukovec²,

Lah³

2015

ACSi

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Dedicated to the memory of Prof. Dr. Jurij V. Bren~i~. AbstractTwo new Mn(III)-salen complexes with 4-aminopyridine (4-apy) have been prepared and structurally characterized.[Mn(ac)(4-apy)(sal)], 1, exhibits mononuclear molecular structure with an octahedral environment around the Mn center. The salen ligand occupies all four basal positions, while the axial sites are occupied by endocyclic nitrogen atom of the 4-apy ligand and acetato oxygen atom. [Mn(4-apy) 2 (sal)]PF 6 , 2, is an ionic compound in which the coordination cations, [Mn(4-apy) 2 (sal)] + , exhibit octahedral geometry. Both axial sites are occupied by endocyclic nitrogen atoms of the 4-aminopyridine ligands. Cations are connected into zig-zag chains via H-bonds. The positive charge is compensated by PF 6 -anions located between the chains.

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“…1,2,6 However, kinetic studies have seldom been carried out. 19 In our experiments, we found that the quantities of catechol, hydroquinone and p-benzoquinone formed were all very small in the catalytic oxidation reaction of phenol when the hydrogen peroxide concentration was 20 times greater than the concentration of phenol. However when the mole ratio of the hydrogen peroxide to phenol was 1:1, the three intermediates, catechol, hydroquinone and p-benzoquinone, clearly appeared in the course of the reaction.…”

Section: Catalytic Oxidation Kinetics Of Catechol Hydroquinone and Pmentioning

confidence: 56%

Studies on the oxidation of phenols catalyzed by a copper(II)–Schiff base complex in aqueous solution under mild conditions

Meng

Zhu

Yan

et al. 2005

J of Chemical Tech & Biotech

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The catalytic oxidation of phenol with hydrogen peroxide using a synthetic copper(II)-Schiff base complex as catalyst has been investigated in phosphate buffer at pH 7 and 25• C. In order to further investigate the reaction pathway, the catalytic oxidation of hydroquinone, p-benzoquinone and catechol were also studied under the same conditions. These reactions were found to be pseudo-first-order with respect to the concentration of phenolic substances. The rate constants were also calculated. In the presence of catalyst, the kinetics and the HPLC analysis showed that for the first step phenol was oxidized to hydroquinone and catechol, and the catalyst easily promoted the formation of hydroquinone but not catechol, for the second step the dihydroxybenzenes were further oxidized to benzoquinone, and lastly short-chain acids, including maleic acid and oxalic acid, were formed. The activity of the catalyst hardly decreased during the whole reaction. Addition of imidazole accelerated the oxidation of phenol. The catalytic decomposition of hydrogen peroxide using this catalyst was also investigated.

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Salen complexes with bulky substituents as useful tools for biomimetic phenol oxidation research

Cited by 37 publications

References 45 publications

Oxidation of Alcohols and Activated Alkanes with Lewis Acid-Activated TEMPO

Oxidation of Alcohols and Activated Alkanes with Lewis Acid-Activated TEMPO

Two new mononuclear manganese(III) salen complexes

Studies on the oxidation of phenols catalyzed by a copper(II)–Schiff base complex in aqueous solution under mild conditions

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