Zur Kenntnis der Huminsäuren, XIV. Mitteilung Bildung und Reaktionen einiger Hydroxy‐chinone

Flaig, Wolfgang; Ploetz, Theodor; Biergans, Hubert

doi:10.1002/jlac.19555970304

Cited by 44 publications

(7 citation statements)

References 8 publications

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“…Catechol 1 is a starting material for the generation of 2,5-dihydroxybenzoquinone 3 (see for instance : Flaig et al 1955). 3 undergoes manifold reactions to higher condensed structures, among them structures such as compounds 8 and 10 (references see there below); it also readily adds primary and secondary amines to give 2-hydroxy-5-amino-[1,4]-benzoquinones, which may then condense to nitrogen-containing heterocycles (Brassard and L'Ecuyer 1958;Manthey et al 1989).…”

Section: Resultsmentioning

confidence: 99%

Discoloration of cellulose solutions in N-methylmorpholine-N-oxide (Lyocell). Part 2: Isolation and identification of chromophores

et al. 2005

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The Lyocell process is a modern 'green' industrial fiber-making technology, which employs N-methylmorpholine-N-oxide monohydrate (NMMO) to directly dissolve cellulose. One problem in Lyocell processing is the discoloration of the spinning dope due to chemical side reactions. Two different methods were elaborated to isolate chromophores, which are present in minute amounts only, from Lyocell fibers, the first one using hydrogen chloride in alcoholic solution, the second one employing boron trifluorideacetic acid complex. Several chromophores were unambiguously identified by a combination of analytical techniques and comparison to authentic samples. Carbohydrate condensation products, such as catechols, were shown to dominate in early phases of chromophore formation. In later stages, these initial chromophores undergo further condensation reactions with degradation products of NMMO and NMMO itself, leading to nitrogen-containing heterocycles and quinoid products, among others. The incorporation of nitrogen into the chromophores and thus the participation of the solvent in chromophore formation were proven.

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Section: Resultsmentioning

confidence: 99%

Discoloration of cellulose solutions in N-methylmorpholine-N-oxide (Lyocell). Part 2: Isolation and identification of chromophores

et al. 2005

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“…Recrystallization from hexane gave 7.5 g (67%) of compound V as a colorless powder, mp 69370oC. 1 2,5-Di-tert-butyl-1,4-benzoquinone (VI) and 3,5-di-tert-butyl-1,2-benzoquinone (VII) were obtained by oxidation of the corresponding diphenols [19].…”

Section: 6-di-tert-butylresorcinol (V)mentioning

confidence: 99%

Reaction of Sterically Congested Phenols and Quinones with Organic Radicals

et al. 2005

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In the course of radiation-induced free-radical transformations of hexane and ethanol, pyrocatechol and hydroquinone derivatives, as well as their respective quinones, are more effective than phenol and resorcinol derivatives in controlling reactions that involve alkyl and hydroxyalkyl radicals. The opposite result takes place in the inhibition by phenols of hexane oxidation in which the key role belongs to the peroxyl radicals generated from the starting compounds.Phenol, di-and polyphenol derivatives are widely known industrial [1] and natural [2] antioxidants, which brings interest in their properties. Considerable attention has been given to correlations between the structure of phenolic compounds and their antioxidant activity. It is commonly accepted that the ability of phenols to inhibit oxidation of organic compounds is determined by their high reactivity toward peroxyl (ROO . ) and other oxygen-centered radicals [1, 2].The main concept we develop in our studies is that processes involving ROO . and other reactive oxygen species are not the only ones responsible for damage of biosystems and industrial materials. Specifically, it was shown that fragmentation of carbon-centered radicals can cause destruction and modification of lipids [3,4], peptides [5], carbohydrates [6], and other biologically important molecules. Peroxide oxidation of synthetic and natural objects, too, begins with generation of carbon-centered radicals from the starting materials. Reactions of carbon-centered radicals with phenolic compounds have scarcely been studied [1,7]. In this connection we have performed a comparative assessment of the reactivity of phenol, di-, and polyphenol derivatives toward oxygen-and carbon-centered radicals [8,9].In the present work we studied the effect of sterically congested phenolic compounds on radiochemical transformations of hexane and ethanol. The resulting data allow us to judge about the reactivity of the compounds studied toward oxygen-and carboncentered organic radicals.It is known that radiolysis of hexane involve reactions leading to hexyl radicals [10] whose recombination gives dodecanes [schemes (1)3(6)].

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“…However, its stereochemistry [(12a) or (12b)l is still obscure. Based on the results described above, the tentative routes for the formation of compound (11) from the azide (3) are as shown in Scheme 5. Unfortunately, it is not yet clear whether the ionic or the radical reaction predominates.…”

Section: Photo-decomposition Ofmentioning

confidence: 99%

Cyclodienones. Part 6. Preparation of 4-azido-2,4,6-tri-t-butyl-cyclohexa-2,5-dienone and its thermal, photo-, and acid-catalyzed decomposition

Fukata¹,

Sakamoto²,

Tashiro³

1982

J. Chem. Soc., Perkin Trans. 1

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Preparation of 4-azido-2,4,6-tri-t-butylcyclohexa-2,5-dienone (3) from 4-bromo-2,4,6-tri-t-butylcyclohexa-2,5-dienone (1 ) and sodium azide is described. Treatment of (3) with concentrated sulphuric acid afforded 2,6-di-t-butyl-p-benzoquinone (7) in 75% yield, while the reaction at -1 0 "C in chloroform solution gave a tri-t-butylazepinone (5) and 3,5-di-t-butyl-o-benzoquinone (8). Photolysis of (3) in benzene afforded 2,4-di-t-butylcyclopenta-2,4-dienone (1 1 ), which was isolated as the dimer (1 2). Thermolysis of (3) in boiling toluene gave 6-amino-2,4-di-t-butylphenol (1 7), 2,4,6,8-tetra-t-butyl-I Hphenoxazin-I -one (21 ), and 2-cyano-9,9a-dihydro-3~5,7,9a-tetra-t-butylcyclopenta[6] [I ,4] benzoxazin-I (3aH)-one (22) in 15, 15, and 48% yields, respectively. When the thermolysis was carried out with very low reagent concentrations, 5-cyano-2,4-di-t-butylcyclopenta-2,4-dienone (23), in addition to the phenol (17), was obtained. The compound (23) was also obtained by thermolysis of (3) in boiling acetic anhydride and in boiling toluene containing acetic anhydride. The reaction pathway for the formation of compounds (1 7), (22), and (23) on thermolysis of the azide (3) is also discussed.It is well known that the decomposition of certain cyclic azides often results in ring expan~ion.~ It has been previously reported that 4-bromo-2,4,6-tri-tbutylcyclohexa-2,5-dienone (1) reacts with nucleophiles such as alcohol^,^ glycol^,^ sodium phenolates,6 and amines ' to afford the corresponding 4-substituted 2,4,6-tri-t-butylcyclohexa-2,5-dienones (2) in good yields. These results suggest that the reaction of the cyclohexadienone (1) with sodium azide may give 4-azido-2,4,6-tri-t-butylcyclohexa-2,5dienone (3).

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Zur Kenntnis der Huminsäuren, XIV. Mitteilung Bildung und Reaktionen einiger Hydroxy‐chinone

Cited by 44 publications

References 8 publications

Discoloration of cellulose solutions in N-methylmorpholine-N-oxide (Lyocell). Part 2: Isolation and identification of chromophores

Discoloration of cellulose solutions in N-methylmorpholine-N-oxide (Lyocell). Part 2: Isolation and identification of chromophores

Reaction of Sterically Congested Phenols and Quinones with Organic Radicals

Cyclodienones. Part 6. Preparation of 4-azido-2,4,6-tri-t-butyl-cyclohexa-2,5-dienone and its thermal, photo-, and acid-catalyzed decomposition

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