Insight into the catalytic activity of alloxazinium and isoalloxazinium salts in the oxidations of sulfides and amines with hydrogen peroxide

Ménová, Petra; Cibulka, Radek

doi:10.1016/j.molcata.2012.07.012

Cited by 28 publications

(16 citation statements)

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“…Some resistant materials can be oxidized using oxidation products containing only water and oxygen, which are compounds that result in minimal environmental damage (Menova and Cibulka 2012;Hartman et al 2015). The standard oxidation reduction potential of H2O2 is 1.8 V, which increases to 2.8 V after treatment with additional reagents (potassium permanganate, hypochlorite, and chlorine dioxide), producing the hydroxyl radical, ·OH.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Microwave-Hydrogen Peroxide Pretreatment of Cellulose

Su¹,

Zhu²,

Wang³

et al. 2016

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A hydrogen peroxide (H2O2) solution was adapted for microwave pretreatment of microcrystalline cellulose, which can be further used for heavy metal adsorption. The H2O2 concentration, temperature, and retention time were the key factors affecting the microwave/hydrogen peroxide pretreatment process. A Box-Benhken design (BBD) with response surface methodology (RSM) was employed to design and optimize the microwave-hydrogen peroxide pretreatment process (H2O2 pretreatment) of cellulose. After the H2O2 pretreatment, the crystallinity of cellulose decreased by 20% and the degree of polymerization (DP) decreased by up to 30%. The optimal conditions obtained by BBD were a H2O2 concentration of 8.37%, a temperature of 90 °C, and a retention time 5.33 min. Under these conditions, a minimum DP of 91.74 was achieved. The results indicated that all three of the factors notably affected the reduction of cellulose polymerization degree and pronounced interactions existed among the response variables. The predictive model developed was able to optimize the pretreatment process for the reduction of cellulose polymerization degree, which could improve the cellulose modification reactivity.

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Section: Introductionmentioning

confidence: 99%

Optimization of Microwave-Hydrogen Peroxide Pretreatment of Cellulose

Su¹,

Zhu²,

Wang³

et al. 2016

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“…Since a proton (H + ) is required for the last step, flavinium catalysts are not active under basic conditions. As a consequence, they have negligible activity in the N‐oxidations of tertiary amines, which proceed by the same mechanism 13…”

Section: Introductionmentioning

confidence: 99%

“…Recently, we have shown that structurally related alloxazinium salts 2a and 2b behave complementarily to 1 in oxidations; they catalyze N‐oxidations, but do not catalyze sulfoxidations 13. This is a result of the change of the rate‐determining step which is, for the oxidations catalyzed by alloxazinium salts, the formation of the hydroperoxide (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

“…This is a result of the change of the rate‐determining step which is, for the oxidations catalyzed by alloxazinium salts, the formation of the hydroperoxide (Scheme ). Nevertheless, there are ways to activate salt 2a for sulfoxidations, for instance, by adding a catalytic amount of a suitable base to the catalytic mixture to allow the formation of the hydroperoxy adduct from the alloxazinium salt, or by using an alloxazine catalyst in the form of an alloxazine‐C4a adduct, for example, 2a‐OCH 3 13. Another efficient procedure developed by Bäckvall14 uses the reduced form, 2a‐H 2 , which is activated by oxygen before entering the catalytic cycle (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

“…Such improved alloxazine‐based catalytic systems show good efficiency in sulfoxidations. However, they are still significantly less efficient than the isomeric isoalloxazinium catalysts 13…”

Section: Introductionmentioning

confidence: 99%

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Electron‐Deficient Alloxazinium Salts: Efficient Organocatalysts of Mild and Chemoselective Sulfoxidations with Hydrogen Peroxide

et al. 2013

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A series of substituted alloxazinium perchlorates has been prepared and tested as catalysts for the oxidation of sulfides to sulfoxides with hydrogen peroxide. The logarithms of the observed rate constants of thioanisole oxidation correlate with the Hammett s constants of the substituents on the alloxazinium catalysts, as well as with their reduction potentials E 0' and their pK R+ values, representing the alloxazinium salt/pseudobase equilibrium. The stronger the electron-withdrawing substituent, the more efficient is the alloxazinium catalyst. The alloxazinium salts with a cyano or trifluoromethyl group in position 8 proved to be the most efficient, operating at room temperature at small loadings, down to 0.1 mol%, achieving turnover number values of up to 640 and acceleration by a factor of 350 relative to the non-catalyzed oxidation. The 8-cyanoalloxazinium perchlorate was evaluated as the best catalyst; however, due to its relatively good accessibility, the 8-(trifluoromethyl)alloxazinium perchlorate seems to be the catalyst of choice for sulfoxidations with hydrogen peroxide. It was successfully tested for the sulfoxidation of a series of aliphatic and aromatic sulfides on a preparative scale. It produced the corresponding sulfoxides in quantitative conversions and with high isolated yields (87-98%). No over-oxidation to sulfone was ever observed.

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Structure and Properties of Flavins

Pavlovska

Cibulka

2021

Flavin‐Based Catalysis

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Insight into the catalytic activity of alloxazinium and isoalloxazinium salts in the oxidations of sulfides and amines with hydrogen peroxide

Cited by 28 publications

References 50 publications

Optimization of Microwave-Hydrogen Peroxide Pretreatment of Cellulose

Optimization of Microwave-Hydrogen Peroxide Pretreatment of Cellulose

Electron‐Deficient Alloxazinium Salts: Efficient Organocatalysts of Mild and Chemoselective Sulfoxidations with Hydrogen Peroxide

Structure and Properties of Flavins

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