Hydride transfer reactions of leuco methylene blue and leuco thionine with some <i>p</i>‐benzoquinones

Yamamoto, Shunzo; Fujiyama, Yoshimichi; Shiozaki, Miki; Sueishi, Yoshimi; Nishimura, Norio

doi:10.1002/poc.610081207

Cited by 13 publications

(10 citation statements)

References 18 publications

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“…Recently, we have studied the kinetics of the reactions of TH and MBH with two-electron oxidants by producing TH and MBH in a closed system by photoreductions of thionine (T ) and methylene blue (MB ) with triethylamine. 15 Kinetics, isotope effects and other evidence have proved that the reactions proceed through stepwise electron-proton-electron (EPE) transfer pathway.…”

Section: Introductionmentioning

confidence: 99%

Kinetic studies on oxidations of leucomethylene blue and leucothionine by iron (III) in aqueous solution

Liu

Yamamoto

Sueishi

1999

J. Phys. Org. Chem.

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The reaction kinetics and mechanism of the oxidations of leucomethylene blue (MBH) and leucothionine (TH) by iron (III) sulfate in aqueous solution were studied spectrophotometrically by the stopped-flow technique. MBH and TH, which were freshly prepared by photoreduction of methylene blue and thionine, respectively, with ascorbic acid were used in the kinetic measurements. The pseudo-first-order rate constants (k obsd ) show kinetic saturation at high initial concentrations of iron (III) sulfate for MBH and TH. It was found that the reciprocal of k obsd increases linearly with increase in the reciprocal of [Fe 3 ] 0 . A broad absorption band was observed on mixing MBH and Fe 3 solutions at low temperatures, and this was attributed to a charge-transfer complex between MBH and Fe 3 . The effects of Fe 2 ion and L-()-ascorbic acid on the rates of oxidation were also investigated. A small kinetic isotope effect on the oxidation rate for MBH was observed. The results can be explained by a general mechanism with stepwise electron-proton-electron transfers with the formation of a complex between reactants.

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Section: Introductionmentioning

confidence: 99%

Kinetic studies on oxidations of leucomethylene blue and leucothionine by iron (III) in aqueous solution

Liu

Yamamoto

Sueishi

1999

J. Phys. Org. Chem.

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“…The reaction occurs only in the micellar interior of the water pool, which accommodates both DMBQ and MBH. Reactions (4)-(7) were proposed for the hydride-transfer reaction between DMBQ and MBH in ethanol in a previous study [14]. According to the reaction mechanism proposed, the reactants DMBQ and MBH are in rapid equilibrium with a charge-transfer complex ((DMBQ−MBH)WP) which is also in rapid equilibrium with the radical ion pair (DMBQ − −MBH + ) formed by the reversible electron transfer from MBH to DMBQ in the complex (reactions (4) and (5)).…”

Section: Resultsmentioning

confidence: 99%

“…Previously, we studied the kinetics of the oxidation of leuco methylene blue (MBH) by some benzoquinones and the Fe 3+ ion spectrophotometrically by means of the stopped-flow technique [14,15]. Since MBH was known to be easily oxidized with dissolved oxygen, kinetic studies on the reactions of this compound with π-acceptors were not previously reported.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Study of the Reaction of Leuco Methylene Blue with 2,6-Dimethyl-p-benzoquinone in a Reverse Micellar System

2008

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The kinetics of the reaction of leuco methylene blue (MBH) with 2, 6-dimethyl-p-benzoquinone (DMBQ) were studied in a heptane/ bis (2-ethylhexyl)sulfosuccinate (AOT)/water reverse micellar system. The pseudo-first-order rate constant (k obsd) obtained in the presence of excess of DMBQ was found to be proportional to the initial concentration of DMBQ for W 0 = 3, 5, 10, 15, and 20 (W 0 = [H 2 O] / [AOT]). The second order rate constant (k 2 = k obsd / [DMBQ] 0) increased with an increase in the W 0-value, but was almost independent of the concentration of the water pool. A mechanism involving the distribution of DMBQ between the reverse micellar interface and bulk organic solvent was proposed to explain these findings.

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“…The trifluoromethylation of 3-methylindole 38 proceeded with good yield at low catalyst concentration, when N,N,N′,N′-tetramethylenediamine (TMEDA) was used as an electron donor. In the presence of 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) as an electron donor, the reaction of terminal alkene 41 with Togni's reagent 39 also gave the hydrotrifluoromethylation product 42 in 67% yield as a major product, because the fully reduced form of MB, leuco-MB, acts as a hydrogen source [49]. The possible mechanism for the catalytic formation of CF 3 radical is shown.…”

Section: Methylene Blue and Acridine Redmentioning

confidence: 99%

Organic Reactions Promoted by Metal-Free Organic Dyes Under Visible Light Irradiation

Miyabe¹

2018

Visible-Light Photocatalysis of Carbon-Based Materials

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Although dyes have received much attention as the visible light-activated photocatalysts, the use of metal-free organic dyes in synthetic organic chemistry is still limited. This chapter summarizes the recent progress in the visible light photocatalysis promoted by metalfree organic dyes. Eosin Y is the typical organic dyes to induce the photoredox catalysis. Recently, other organic dyes such as Rose Bengal, fluorescein, and methylene blue have been studied as photocatalysts to promote the single-electron transfer processes.

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Hydride transfer reactions of leuco methylene blue and leuco thionine with some p‐benzoquinones

Cited by 13 publications

References 18 publications

Kinetic studies on oxidations of leucomethylene blue and leucothionine by iron (III) in aqueous solution

Kinetic studies on oxidations of leucomethylene blue and leucothionine by iron (III) in aqueous solution

Kinetic Study of the Reaction of Leuco Methylene Blue with 2,6-Dimethyl-p-benzoquinone in a Reverse Micellar System

Organic Reactions Promoted by Metal-Free Organic Dyes Under Visible Light Irradiation

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