Reactivity of Substituted Phenols Toward Alkyl Radicals

Franchi, Paola; Lucarini, Marco; Pedulli, Gian Franco; Valgimigli, Luca; Lunelli, Bruno

doi:10.1021/ja982405d

Cited by 84 publications

(86 citation statements)

References 39 publications

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“…The logarithms of the rate constants for H-atom abstraction are known to be inversely proportional to the BDE(O-H)s. The slope and the y-intercept of these plots are dependent on the nature of the abstracting radicals and on the steric crowding around the phenolic OH group, respectively. [30,32,33] In Figure 5 it is shown that 5b-d are on the same line of unhindered phenols, this being consistent with the presence, in ortho position to the OH group, of only one methyl group in 5b,c and with the absence of any substituent in 5d. Compound 5a is near to the line of 2,6-dimethylphenols, as expected from its structure.…”

Section: Resultssupporting

confidence: 68%

A Straightforward Hetero‐Diels–Alder Approach to (2‐ambo,4′R,8′R)‐α/β/γ/δ‐4‐Thiatocopherol

et al. 2010

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A simple and original inverse electron demand hetero‐Diels–Alder reaction has been successfully applied to the synthesis of (2‐ambo,4′R,8′R)‐α/β/γ/δ‐4‐thiatocopherol. Commercially available methyl hydroquinones and (2E,7R,11R)‐(+)‐phytol were exploited for the preparation of the ortho‐thioquinones, acting as electron‐poor dienes, and of the proper 1,3‐diene used as dienophile, respectively. The benzoxathiine cycloadducts, with the required tocopherol‐like skeleton, were obtained with complete control of regio and chemoselectivity. The antioxidant activity of 4‐thiatocopherols was measured and rationalized in comparison with that of the corresponding natural components of Vitamin E.

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Section: Resultssupporting

confidence: 68%

A Straightforward Hetero‐Diels–Alder Approach to (2‐ambo,4′R,8′R)‐α/β/γ/δ‐4‐Thiatocopherol

et al. 2010

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“…Even steric protection of the OH group in 2,6-di-tert-butylphenols does not prevent the formation of a hydrogen bond with suitable acceptors, [27] although 1e is often described [28] as a molecule that does not form hydrogen bonds even with strong hydrogen-bond acceptors. Phenols 1a-e have high BDE values when compared to the H-O BDE in nitrous acid and also a fairly good tendency to form hydrogen bonds with the solvent, as indicated by their α H 2 values.…”

Section: Resultsmentioning

confidence: 99%

New Insights into the Reactivity of Nitrogen Dioxide with Substituted Phenols: A Solvent Effect

2005

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Various alkyl‐substituted phenols react readily with nitrogen dioxide (·NO2) in different solvents at room temperature. In all cases nitration is the major reaction and leads to the formation of mono‐ and dinitrophenols and 4‐nitrocyclohexa‐2,5‐dienones from 2,4,6‐tri‐substituted phenols. Oxidation, dimerisation and, in one case, nitrosation are also observed. The reaction pathway followed changes according to the solvent and to the nature and the number of substituents on the phenolic ring. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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“…Judging from recent data reported by Pedulli et. al., [39] k 2 should be around 10 6  -1 s -1 at 600 K. This can be followed by combination of phenoxy with methyl radicals to give anisole, plus o-/p-cresols, the latter two compounds after tautomerisation of the respective keto forms (Equation 3). [14] CH 3…”

Section: Discussion (A) Radical-induced Lower-temperature Approachesmentioning

confidence: 99%

Products, Rates, and Mechanism of the Gas-Phase Condensation of Phenoxy Radicals between 500-840 K

Wiater¹,

Born

Louw

2000

Eur. J. Org. Chem.

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Phenols are demonstrated precursors of “dioxins” ‐ polychlorinated dibenzo‐p‐dioxins (DDs) and dibenzofurans (DFs) ‐ in thermal processes, especially incineration. Heterogeneous catalysis, depending on conditions, can play an important role, but mere gas‐phase combination of phenolic entities to ultimately DD and/or DF is always possible. The present paper addresses the fundamental role of phenol itself. Phenol has long been known to give DF upon pyrolysis and in similar thermal reactions. In the liquid phase under oxidative conditions it yields five condensation products (A‐E); this clearly occurs through the dimerization of two phenoxy (PhO) radicals, followed by enolisation/rearomatisation. Our study shows that in the gas phase, at the lower T end, such dimers are also formed, but still with very little DF. That DF, indeed, is almost the only condensation product at elevated temperatures is substantiated by thermochemical‐kinetic analysis (favouring the pathway of ortho‐C/ortho‐C combination of two PhO radicals), as well as by results obtained with two plausible intermediates, viz. 2,2′‐dihydroxybiphenyl (A) and 2‐phenoxyphenol (C). Mechanisms for the requisite enolisation and dehydration steps leading to DF are discussed.

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Reactivity of Substituted Phenols Toward Alkyl Radicals

Cited by 84 publications

References 39 publications

A Straightforward Hetero‐Diels–Alder Approach to (2‐ambo,4′R,8′R)‐α/β/γ/δ‐4‐Thiatocopherol

A Straightforward Hetero‐Diels–Alder Approach to (2‐ambo,4′R,8′R)‐α/β/γ/δ‐4‐Thiatocopherol

New Insights into the Reactivity of Nitrogen Dioxide with Substituted Phenols: A Solvent Effect

Products, Rates, and Mechanism of the Gas-Phase Condensation of Phenoxy Radicals between 500-840 K

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