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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1984 (1984), S. 929-938 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Dehydration Reactions with Gallic Acid EstersGallic acid methyl ester (1) is oxidized by horseradish peroxidase giving the benzotropolone compound 3 and dimethyl 3,3′,4,4′,5,5′-hexahydroxy-2,2′-diphenate (2) which easily forms ellagic acid (4). By the analgous reaction with the gallic acid esters of ethanediol, 1,3-propanediol, 1,4-butanediol, trans-1,2-cyclohexanediol, 3,6-digalloylglucose, and pentagalloylglucose only 4 is formed. Oxidation of 1 by air in alkaline medium yields 4 and the 1-benzofuran derivative 9. If 9 is treated with alkali the furan ring is opened to give an intermediate from which the acconitic acid derivative 11 or the naphthalene system 12 or the benzoxepine compound 14 are obtained. By oxidation of 1 with iron(III) chloride the furan 15 is obtained.
    Notes: Gallussäure-methylester (1) liefert mit Meerrettich-Peroxidase den 3,3′,4,4′,5,5′-Hexahydroxy-2,2′-diphensäure-dimethylester (2), der leicht in Ellagsäure (4) übergeht, sowie Purpurogallin-4-carbonsäure-methylester (3). Die analoge Reaktion mit den Digalloylestern von Ethandiol, 1,3-Propandiol, 1,4-Butandiol, trans-1,2-Cyclohexandiol, 3,6-Digalloylglucose und Pentagalloylglucose führt nicht zu den Diphensäurederivaten, sondern nur zu 4. Luftoxidation von 1 in alkalischem Milieu führt teils zu 4, zum anderen Teil zum 1-Benzofuranderivat 9, dessen bemerkenswerte Reaktionen beschrieben werden. Unter Einwirkung von Alkali wird zunächst der Furanring geöffnet, und von hier aus gelangt man zum Acconitsäurederivat 11, zum Naphthalinsystem 12 oder zur Benzoxepinverbindung 14. Mit Eisen(III)-chlorid als Oxidationsmittel wird aus 1 Ellagsäure (4) und das Furanderivat 15 erhalten.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 56 (1973), S. 1948-1955 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The racemic trans-β-ionone-epoxide (7) upon irradiation with light of wavelength 254 nm (in pentane solution) gives rise to novel photochemical processes and formation of compounds 12, 13, 14, and 15.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 916-920 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dihydroactinodiolid 1 is formed in high yields by oxidation of the alcohols 2 and 3 and the ether 4. Furthermore, the oxidation of the epoxy-alcohols 13 and 14 gives rise to the formation of furancompounds (15 and 16, respectively).
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lead tetraacetate (LTA) oxidation of the allylic alcohols 1, 10, 14 and 19 leads to the formation of the epoxides 2, 11, 15 and 20, products of a novel internal addition reaction of the electron deficient alcohol oxygen to the allylic double bond. In some cases (10, 14) the formation of a new type of acetoxylated enolethers (12, 16) is observed. The LTA oxidation of the allylic dienols 21 and 29 gives rise to the formation of the epoxyacetates 25 and 33, products of a similar internal addition reaction. Furthermore, a variety of cyclization products (22, 23, 24, 26, 30, 31, 32 and 34) has been isolated whose formation requires an isomerisation of the allylic trans double bond to a cis one.
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  • 5
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lead tetraacetate (LTA) oxidation of dihydro-γ-jonol (2) gives the new bicyclic ether 4 in high yield. On the other hand, LTA oxidation of the alcohols 8, 14, 20, results in the formation of complex mixtures of oxidation products, from which the spiro compounds 10, 16, 22, the bicyclic ethers 11, 12, 17, 18, 23, and the carbonyl compounds 13, 19 have been isolated.
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  • 6
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: UV.-irradiation of iso-methyl-α, (E)-ionone (4) in neutral solvents yields iso-methyl-α, (Z)-ionone (5), the bicyclic ether 6 and the epoxide 7 by a sequence of successive photoisomerizations. The steps leading to des-methyl homologues of 6 and 7 do not occur on irradiation of α, (E)-ionone (1) [10]. The reversible isomerization 4 ⇄ 5 is followed by the irreversible photoprocess 5 → 6 and the final transformation 6 → 7. Irradiation of iso-methyl-α, (E)-ionone (4) in acidic or basic solvents leads to a deep change in the type of products and gives the isomeric ketones 9 and 10 in high yields. A tentative mechanism for the photoisomerization steps 5 → 6, 6 → 7 and 5 → 9 + 10 is proposed.
    Additional Material: 2 Tab.
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  • 7
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of Conjugated δ-Keto-enones and β,γ,δ,∊-Unsaturated KetonesOn 1π,π*-excitation the δ-keto-enones 5-8 are isomerized to compounds B (18, 22, 26, 28) via 1,3-acyl shift and to compounds C (19, 23, 27, 29) via 1,2-acyl shift, whereas the β,γ,δ,∊-unsaturated ketone 9 gives the isomers 32 and 33 by 1,2-and 1,5-acyl shift, respectively. Furthermore, isomerization of 6 to 24, dimerization of 8 to 30 and addition of methanol to 8 (8 → 31) is observed. Unlike 7 and 8 the acyclic ketones 5, 6 and 9 undergo photodecarbonylation on 1π,π*-excitation (5 → 20, 21; 6 → 20, 25; (E)-9 → 35-38).Evidence is given, that the conversion to B as well as the photodecarbonylation of 5,6 and 9 arise from an excited singulet state, but the conversion to C as well as the dimerization of 8 from the T1-state.
    Additional Material: 3 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 1520-1537 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of γ,δ-Methano-α-enonesDirect excitation (λ = 254 or ≥ 347 nm) converts the γ,δ-methano-α-enone (E)-10 into the isomeric ether 23 and the isomeric diene-ketone 24. Furthermore, on 1π,π*-excitation (λ = 254 nm) (E)-10 undergoes an 1,3-homosigmatropic rearrangement yielding the enone (E)-25. In addition (E → Z)-isomerization of (E)-10 and conversion of 10 to the isomeric furan 28 is observed.The isomerization (E)-10 → 23, 24 and (E)-25 proceeds by photocleavage of the C(γ), C(δ)-bond, whereas the formation of 28 occurs by photocleavage the C(γ), C(δ)-bond together with that of the C(γ), C(δ′)-bond of 10.On direct excitation the bicyclic diene-ether 23 yields the methano-enone 10, the dieneketone 24 and the tricyclic ether 29. Evidence is given, that the conversion 23 → 10 is a singulet process. On the other hand, the isomerization 23 → 24 and the intramolecular [2 + 2]-photocycloaddition 23 → 29 are shown to be triplet reactions.Irradiation (λ = 254 nm) of the homoconjugated ketone 24 yields the isomeric ketone 27 by an 1,3-acyl shift. The excitation of the (E)-enone 25 induces (E → Z)-isomerization and photoenolization to give the homoconjugated ketone 26.
    Additional Material: 1 Tab.
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  • 9
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Photochemistry of Conjugated γ,δ-Epoxy-ene-carbonyl Compounds of the Ionone Series: UV.-Irradiation of α,β-Unsaturated ε-Oxo-γ,δ-epoxy Compounds and Investigation of the Mechanism of the Isomerization of Epoxy-enones to FuranesOn 1n, π*-excitation (λ ≥ 347 nm; pentane) of the enonechromophore of 3, three different reactions are induced: (E/Z)-isomerization to give 13 (7%), isomerization by cleavage of the C(γ)-C(δ) bond to yield the bicyclic ether 14 (36%) and isomerization by cleavage of the C(γ)—O bond to give the cyclopentanones 15 (13%) and 16 (11%; s. Scheme 2). On 1π, π*-excitation (λ = 254 nm; acetonitrile) 13 (14%), 15 (6%), and 16 (6%) are formed, but no 14 is detected. In contrast, isomerization by cleavage of the C(δ)—O bond to give the cyclopentanone 17 (23%) is observed. The reaction 3→17 appears to be the consequence of an energy transfer from the excited enone chromophore to the cyclohexanone chromophore, which then undergoes β-cleavage. Irradiation of 4 with light of λ = 254 nm (pentane) yields the analogous products 20 (18%), 21 (9%), 22 (7%), and 24 (7%; s. Scheme 2). Selective 1n, π*-excitation (λ ≥ 280 nm) of the cyclohexanone chromophore of 4 induces isomerization by cleavage of the C(δ)—O bond to give the cyclopentanones 23 (9%) and 24 (44%). Triplet-sensitization of 4 by excited acetophenone induces (E/Z)-isomerization to provide 20 (12%) and isomerization by cleavage of the C(δ)—O bond to yield 21 (26%) and 22 (20%), but no isomerization via cleavage of the C(δ)—O bond.It has been shown, that the presence of the ε;-keto group facilitates C(γ)—C(δ) bond cleavage to give a bicyclic ether 14, but hinders the epoxy-en-carbonyl compounds 3 and 4 from undergoing cycloeliminations.The activation parameters of the valence isomerization 13 → 18, a thermal process, have been determined in polar and non-polar solvents by analysing the 1H-NMR. signal intensities. The rearrangement proceeds faster in polar solvents, where the entropy of activation is about -20 e.u. Opening of the epoxide ring and formation fo the furan ring are probably concerted.
    Additional Material: 5 Tab.
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  • 10
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Photoinduced Cleavage of Conjugated γ, δ-Epoxyenones: UV.-Irradiation of 5,6-Epoxy-3, 4-didehydro-5,6-dihydro-β-iononeOn 1n, π*-excitation (λ ≥ 347 nm) in pentane or CClF2CFCl2 (E)-1 is isomerized to the dihydrofurane (E/Z)-2 as well to the ethers 3 and 5. Besides these products the isomeric cyclopropane derivative (E)-4 and the acetal 6 are obtained in methanol. The detection of 6 indicates the formation of an intermediate ketoniumylide a which may give 6 by addition of methanol. - On 1π, π*-excitation (λ=254 nm) in acetonitrile-d3, CClF2CFCl2 or pentane (E)-1 yields almost exclusively (E)-2. In methanol 6 is obtained in addition to (E/Z)-2, but no (E)-4 and 5 is formed.
    Additional Material: 1 Tab.
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