- Revising the Role of a Dioxirane as an Intermediate in the Uncatalyzed Hydroperoxidation of Cyclohexanone in Water
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The mechanism of the oxidation of cyclohexanone with an aqueous solution of hydrogen peroxide has been investigated. Experiments revealed the preliminary formation of an intermediate, identified as cyclohexylidene dioxirane, in equilibrium with the ketone, followed by formation of 1-hydroperoxycyclohexanol (Criegee adduct). Computational analysis with explicit inclusion of up to two water molecules rationalized the formation of the dioxirane intermediate via addition of the hydroperoxide anion to the ketone and revealed that this species is not involved in the formation of the Criegee adduct. The direct addition of hydrogen peroxide to the ketone is predicted to be favored over hydrolysis of the dioxirane, the latter in competition with ring opening to carbonyl oxide followed by hydration. However, dioxirane may account for the formation of the bis-hydroperoxide derivative.
- Rozhko, Elena,Solmi, Stefania,Cavani, Fabrizio,Albini, Angelo,Righi, Paolo,Ravelli, Davide
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- Total synthesis of (+)-petromyroxol via tandem α-aminoxylation-allylation and asymmetric dihydroxylation-SN2 cyclization approach
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The total synthesis of (+)-petromyroxol, a tetrahydrofuran (THF)-diol fatty acid, isolated from sea lamprey larvae (Petromyzon marinus) is reported. The present synthesis employs a tandem α-aminoxylationallylation, cross metathesis and tandem asymmetric d
- Nookaraju,Kumar, Pradeep
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p. 63311 - 63317
(2015/08/06)
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- Hydrogen peroxide and arenediazonium salts as reagents for a radical beckmann-type rearrangement
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The reductive ring-opening of hydroperoxides derived from cyclic ketones leads to alkyl radicals which can effectively be trapped by arenediazonium salts. This synthetic transformation yielding azo carboxylic acids or lactams, after a reductive step, can be classified as a radical version of the well-known Beckmann rearrangement. In this article, we present results on the scope, the limitations and possible applications of this new reaction type. Georg Thieme Verlag Stuttgart · New York.
- Prechter, Agnes,Heinrich, Markus R.
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experimental part
p. 1515 - 1525
(2011/06/24)
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- Pathways of liquid-phase oxidation of cyclohexanol
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The kinetics of product accumulation in uncatalyzed oxidation of cyclohexanol at 403 K was studied. Along with the compounds originating from oxidation of cyclohexanol at position 1 (cyclohexanone, hydrogen peroxide, 1-hydroxycyclohexyl hydroperoxide), products formed by oxidation of C-H bonds at positions 2-4 were detected: 2-, 3-, and 4-hydroxycyclohexyl hydroperoxides (cis and trans isomers), 1,2-, 1,3-, and 1,4-dihydroxycyclohexanes (cis and trans isomers), 2- and 4-hydroxycyclohexanones, and 2-cyclohexenone.
- Puchkov,Buneeva,Perkel'
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p. 248 - 253
(2007/10/03)
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- Preparation of 2-(6-carboxyhexyl)- and 2-(6-methoxycarbonylhexyl)cyclopent-2-en-1-one using free radical reactions
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Two short and simple synthetic routes to the prostaglandin synthons 2-(6-carboxyhexyl)- and 2-(6-methoxycarbonylhexyl)cyclopent-2-en-1-one have been developed. The first is based on a cyclohexanone oxidative transformation with hydrogen peroxide and di-tert-butyl peroxide, the second on the free radical addition reaction of methyl 9-oxononanoate to acrylaldehyde diacylal.
- Ogibin,Starostin,Aleksandrov,Pivnitsky,Nikishin
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p. 901 - 903
(2007/10/02)
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- Electron-transfer reactions of alkyl peroxy radicals
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One-electron-transfer reactions of alkyl peroxy radicals were studied by pulse radiolysis of aqueous solutions. At pH 13, the methyl peroxy radical was found to rapidly, k = 1 × 105-4.9 × 107 s-1, and quantitatively oxidize various organic substrates with E13 = 0.13-0.76 V vs NHE. On the other hand, this radical was unreactive with compounds with E13 ≥ 0.85 V. Consequently, E13 of the methyl peroxy radical is higher than 0.76 V and lower than 0.85 V, which means that E7 is in the range 1.02-1.11 V. At pH 8, the rate constants of the oxidation of four ferrocene derivatives by the alkyl peroxy radicals ranged from 7.1 × 104 M-1 s-1 for ferrocenedicarboxylate (E8 = 0.66 V) to 2.3 × 106 M-1 s-1 for (hydroxymethyl)ferrocene (E8 = 0.42 V). These rate constants were used to evaluate the reduction potential and self-exchange rate of alkyl peroxy radicals in neutral media from the Marcus equation. The calculated E7 = 1.05 V is in excellent agreement with the estimated E7 = 1.02-1.11 V and with one of the perviously published values E7 = 1.0 V, but the value is in excellent agreement higher than the other E7 ~ 0.6 V. It is suggested that the high reorganization energy, λ = 72 kcal mol-1 redox couple originates from the requirement for solvent reorganization due to the solvation of hydroperoxide anion in the transition state. In support of this are the activation parameters of the reaction of the methyl peroxy radical with uric acid. The activation entropy is 9 eu lower at pH 7.3 than it is at pH 13.2, whereas the activation enthalpies are unchanged. The importance of entropy control was verified in the reactions of cyclohexyl peroxy radicals with α- and δ-tocopherol in aerated cyclohexane (ΔH+ ≈ 0 kcal/mol, and ΔS+ = -25 and -26 eu). The implications of these findings on the inactivation of alkyl peroxy radicals in general are discussed.
- Jovanovic, Slobodan V.,Jankovic, Ivana,Josimovic, Ljubica
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p. 9018 - 9021
(2007/10/02)
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- INFLUENCE OF CARBOXYLIC ACIDS ON THE COURSE AND RATE OF THE INITIAL STAGE OF CYCLOHEXANOL OXIDATION.
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Addition of carboxylic acids to cyclohexanol undergoing oxidation at 120 degree raises the reaction rate and the relative rate of formation of alpha -hydroxycyclohexyl hydroperoxide; the magnitude of this effect depends on the strength of the acid. Introduction of adipic acid in various concentrations at the start of cyclohexanol oxidation raises the oxidation rate and lowers the maximum concentrations of alpha -hydroxycyclohexyl hydroperoxide and hydrogen peroxide, but does not affect the ratio of the initial rates of formation of alpha -hydroxycyclohexyl hydroperoxide and hydrogen peroxide.
- Neginskaya,Freidin
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p. 2525 - 2529
(2007/10/02)
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