Studies on the Autoxidation of t-Butyl-substituted Phenols in Alkaline Media. 2. Reactions of 4,6-Di-t-butylguaiacol and Related Compounds.

Gierer, Josef; Imsgard, Finn; Nishida, Toshiaki; Enzell, Curt R.; Christensen, A.; Schroll, Gustav

doi:10.3891/acta.chem.scand.31b-0546

Cited by 14 publications

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This result is surprising in view of the great extent of ring opening observed when phenolic structures are reacted with molecular oxygen, which is a considerably weaker oxidant (Eckert et al 1973, Gierer andImsgard 1977). The reason for this discrepancy is currently being studied in this laboratory.…”

mentioning

confidence: 44%

The Reactions of Hydroxyl Radicals with Aromatic Rings in Lignins, Studied with Creosol and 4-Methylveratrol

Gierer¹,

Yang²,

Reitberger³

1992

Holzforschung

Self Cite

View full text Add to dashboard Cite

Creosol and its methyl ether (4-methylveratrol), two simple model compounds representing phenolic and non-phenolic nuclei in lignins, were reacted in aqueous solution at ambient temperature and pressure with hydroxyl radicals generated by -radiolysis. The reactions were conducted at different pH levels (2-12) and in the presence and absence of oxygen. After fractionation of the reaction mixtures, more than 40 products from each model compound were identified by HPLC-UV, GC-MS and/or NMR analyses. In some cases the data were compared with those of corresponding authentic samples. On the basis of the composition of the reaction mixtures, the most important reaction modes were identified äs oxidative coupling, demethoxylation, hydroxylation and oxidation of the methyl group. Surprisingly, only small yields of ring opening products were found, even when the reactions were run in the presence of oxygen. The mechanisms of the observed types of reaction are discussed and the influence of pH and of oxygen on the product pattern and on the rate of Substrate consumption is tentatively interpreted.

show abstract

mentioning

confidence: 44%

The Reactions of Hydroxyl Radicals with Aromatic Rings in Lignins, Studied with Creosol and 4-Methylveratrol

Gierer¹,

Yang²,

Reitberger³

1992

Holzforschung

Self Cite

View full text Add to dashboard Cite

show abstract

“…There are no simple mechanisms that would justify such reorganization, but a similar conversion is precedented by the outcome of base-mediated autoxidation of 4,6-di- tert -butylguaiacol . In analogy with this work, we consider the intermediacy of a dioxetane that decays to an epoxide, opening of which would provide the “driving” force for migration of the tert -butyl group.…”

Section: Resultsmentioning

confidence: 99%

Novel tert-Butyl Migration in Copper-Mediated Phenol Ortho-Oxygenation Implicates a Mechanism Involving Conversion of a 6-Hydroperoxy-2,4-cyclohexadienone Directly to an o-Quinone

et al. 2000

View full text Add to dashboard Cite

Copper mediated ortho-oxygenation of phenolates may proceed through the generation of a 6-peroxy-2,4-cyclohexadienone intermediate. To test this theory, we studied the fate of sodium 4-carbethoxy-2, 6-di-tert-butylphenolate, where the ortho-oxygenation sites are blocked by tert-butyl groups. Using the Cu(I) complex of N, N-bis(2-(N-methylbenzimidazol-2-yl)ethyl)benzylamine, isolation of the major oxygenated product and characterization by single-crystal X-ray crystallography and NMR spectroscopy revealed it to be 4-carbethoxy-3,6-di-tert-butyl-1,2-benzoquinone, resulting from a 1, 2-migration of a tert-butyl group. The independently prepared 6-hydroperoxide is transformed by the Cu(I)- (or Cu(II)-) ligand complex to the same o-quinone. The observed 1,2-migration of the tert-butyl group appears to reflect an electron demand created by rearrangement of the postulated peroxy intermediate. A mechanism proceeding alternatively through a catechol and subsequent oxidation to the o-quinone seems ruled out by a control study demonstrating that the requisite intermediate to catechol formation would instead eliminate the 2-tert-butyl group.

show abstract

“…Photooxidation of 3,5-di-t-butyl catechol 5a in polar solvents such as methanol, acetone or aceto-$Treatment of 4a with Na,CO, at room temperature gives a new product. Although we did not investigate this reaction in detail, we assign the epoxide structure 6 based on ' H NMR and comparison with analogous products reported in the literature (Gierer and Imsgard, 1977a, 1977b, Wilson et al, 1982. 'H NMR: 6.83 (d, J = 1 Hz, lH), 3.78 (d, J = 1 Hz, lH), 1.15 (s, 9H), 1.01 (s, 9H).…”

Section: Resultsmentioning

confidence: 99%

CHEMISTRY OF SINGLET OXYGEN—48. ISOLATION and STRUCTURE OF THE PRIMARY PRODUCT OF PHOTOOXYGENATION OF 3,5‐DI‐t‐BUTYL CATECHOL

Jensen

Foote

1987

Photochem & Photobiology

View full text Add to dashboard Cite

The dye-sensitized photooxygenation of r-butyl substituted catechols has been investigated. The primary product from 3.5-di-r-butyl catechol has been isolated and shown to be a hydroperoxydienone by single crystal X-ray diffraction. The absence of sensitizer effects and the faster reaction rate in polar solvents suggest that the reaction proceeds with singlet oxygen as the primary oxygenating species. Charge-transfer or full electron-transfer from the catechol to singlet oxygen is probably involved. Substituent effects are in agreement with this mechanism. The products from thermal breakdown of the hydroperoxydienone are inconsistent with a Baeyer-Villiger mechanism.i t e l (Hamilton, i974).The base-catalyzed quinones, resorcinols,

show abstract

Studies on the Autoxidation of t-Butyl-substituted Phenols in Alkaline Media. 2. Reactions of 4,6-Di-t-butylguaiacol and Related Compounds.

Cited by 14 publications

References 0 publications

The Reactions of Hydroxyl Radicals with Aromatic Rings in Lignins, Studied with Creosol and 4-Methylveratrol

The Reactions of Hydroxyl Radicals with Aromatic Rings in Lignins, Studied with Creosol and 4-Methylveratrol

Novel tert-Butyl Migration in Copper-Mediated Phenol Ortho-Oxygenation Implicates a Mechanism Involving Conversion of a 6-Hydroperoxy-2,4-cyclohexadienone Directly to an o-Quinone

CHEMISTRY OF SINGLET OXYGEN—48. ISOLATION and STRUCTURE OF THE PRIMARY PRODUCT OF PHOTOOXYGENATION OF 3,5‐DI‐t‐BUTYL CATECHOL

Contact Info

Product

Resources

About