Intramolecular homolytic displacements. Part 29: induced decompositions of 4,5-ethylenic peroxyketals

Ramon, Fabienne; Degueil-Castaing, Marie; Bevilacqua, Marcel; Maillard, B.

doi:10.1039/a909434b

Cited by 6 publications

(3 citation statements)

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“…The participation of 1,4-dioxane as a hydrogen donor is in the literature (43)(44)(45)(46)(47)(48)(49)(50)(51), and its hydrogen transfer reaction to carbonyl triplets has been studied by Previtali and Scaiano (43), who measured the rate constant for hydrogen abstraction (k H ) by triplet benzophenone from 1,4-dioxane as 4.27 ϫ 10 5 M Ϫ1 s Ϫ1 . We measured the same parameter for hydrogen abstraction from 1,4-dioxane by 3-benzoyl pyridine in water and obtained k H ϭ 2.0 ϫ 10 6 M Ϫ1 s Ϫ1 , thus confirming the relatively high reactivity of carbonyl triplet states toward 1,4-dioxane.…”

Section: Nanosecond Laser Flash Photolysismentioning

confidence: 99%

A Laser Flash Photolysis Study of Curcumin in Dioxane-Water Mixtures¶

Ortica

Rodgers

2001

Photochemistry and Photobiology

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Curcumin [bis(4‐hydroxy‐3‐methoxyphenyl)‐1,6‐heptadiene‐3,5‐dione] was studied by means of UV–VIS absorption spectroscopy and nanosecond laser flash photolysis in 1,4‐dioxane–water mixtures in a series of dioxane–water volume ratios. The transient characteristics were found to be dependent on the amount of water. In pure dioxane the triplet state of the molecule in its enolic form was detected (λmax= 720 nm, τ= 3.2 μs), whereas upon water addition, the diketo form was found to prevail, because of the perturbation of intramolecular H‐bonded structure. This led to hydrogen abstraction from dioxane by curcumin triplet state and the formation of the corresponding ketyl radical (λmax= 490 nm, τ∼ 10 μs). Laser flash photolysis measurements, carried out in solvents of different polarity and proticity (benzene, cyclohexane and various alcohols), allowed the transient assignments to be confirmed, supporting our interpretation.

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Section: Nanosecond Laser Flash Photolysismentioning

confidence: 99%

A Laser Flash Photolysis Study of Curcumin in Dioxane-Water Mixtures¶

Ortica

Rodgers

2001

Photochemistry and Photobiology

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“…Free radical chemistry, based on the induced decomposition of unsaturated peroxy derivatives, has been developed in our group. 1 In particular, the free radical decomposition of unsaturated "acrylic" peroxides was used to synthesize glycidic esters 2 (Scheme 1). The mechanism involves the addition of a carbon-centered radical, obtained by abstraction of an hydrogen atom from the solvent ZH by 1,1-dimethylethoxyl radicals, to the carbon-carbon double bond of the peroxide.…”

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confidence: 99%

“…Free radical chemistry, based on the induced decomposition of unsaturated peroxy derivatives, has been developed in our group . In particular, the free radical decomposition of unsaturated “acrylic” peroxides was used to synthesize glycidic esters (Scheme ).…”

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confidence: 99%

Carbanion-Induced Decompositions of β,γ-Unsaturated Peroxides Containing Electron-Deficient Double Bonds

2001

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The treatment of a beta,gamma-unsaturated peroxide, containing an electron-deficient double bond, by a carbanion Z(-) led to the transformation of the compound by a process involving the addition of the carbanion to the double bond, followed by an S(N)i reaction on the peroxidic bond, with the liberation of an alkoxylate anion. When the carbanion was regenerated by proton abstraction from a ZH substrate by this oxyanion, the anionically induced decomposition occurred using catalytic amounts of sodium ethoxylate to initiate it. When this abstraction was not efficient, stoichiometric amounts of carbanion were necessary to decompose the unsaturated peroxide. These induced decompositions are a good source of epoxides, which were the end reaction products. However, in some cases, this heterocycle could give secondary reactions as a result of the attack of the liberated 1,1-dimethylethoxylate on it. The importance of these reactions depended upon the nature of the precursor of carbanion ZH.

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