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  • Organic Chemistry  (20)
  • 1980-1984  (20)
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  • 1
    Electronic Resource
    Electronic Resource
    Dehydrierungsreaktionen mit Gallussäureestern (1984)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1984 (1984), S. 929-938 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198419840512
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  • 2
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen. 109. Mitteilung [1]. Zur Photochemie konjugierter δ-Keto-enone und β,γ,δ,∊-ungesättigter Ketone (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 1499-1519 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630620
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  • 3
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen. 110. Mitteilung [1]. Zur Photochemie γ,δ-Methano-α-enone (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 1520-1537 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630621
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  • 4
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen 113. Mitteilung [1]. Zur Photospaltung konjugierter γ, δ-Epoxyenone: UV.-Bestrahlung von 5, 6-Epoxy-3,4-didehydro-5,6-dihydro-β-jonon (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 2212-2220 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630811
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  • 5
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen. 117. Mitteilung [1] Zur Photochemie von 5,6-EpoxydienenTeil III; bzgl. Teil II s. [2]. und konjugierten 5,6-EpoxytrienenVgl. vorläufige Mitt. [3]. (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 198-214 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of 5,6-Epoxydienes and of Conjugated 5,6-EpoxytrienesOn singulet excitation (δ = 254 nm) the 5,6-epoxydiene 6 and the conjugated 5,6-epoxytrienes 7 and 8 exclusively give products arising from cleavage of the C, C-bond of the oxirane (cf. 6→9, 10, 11; 7→ (E)-15, 16, 17; 8→ 18 (A+B), 19 (A+B), 20, 21). The dihydrofuran compounds 11 and (E/Z)-15 are formed by cyclization of a ketonium-ylide a and d, respectively. Photolysis of a gives the carbene b which yields the cyclopropene 9, whereas d forms photochemically the carbenes f and g which yield the methano compounds 16 and 17. The isomeric cyclopropene derivatives 20 and 21 are products of the intermediates h and i, respectively, which are formed by photolysis of the ylide e. The cyclopropene 21 isomerizes by intramolecular cycloadditions to 18 (A+B) and 19 (A+B). - On triplet excitation (λ≥LD nm; 280 nm; acetone) 6 undergoes cleavage of the C(5), O-bond and isomerizes to 12 and 14. However, 7 is converted by cleavage of the C, C-bond of the oxirane to yield 15. On treatment with BF3O(C2H5)2 6 gives 14, whereas 7 yields 22, and 8 forms 23 and 24.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640122
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  • 6
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen. 118. Mitteilung [1] Zur vinylogen β-Spaltung von Enonen. UV.-Bestrahlung von 4-(3',7',7'-Trimethyl-2'-oxabicyclo [3.2.0]hept-3'-en-1'-yl)but-3-en-2-on (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 215-223 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vinylogous β-Cleavage of Enones: UV.-irradiation of 4-(3′,7′,7′-trimethyl-2′-oxabicyclo[3.2.0]hept-3′-ene-1′-yl)but-3-ene-2-onOn 1π,π*-excitation (λ = 254 nm) in acetonitrile (E/Z)-2 is converted into the isomers 4-9 and undergoes fragmentation yielding 10; in methanol (E/Z)-2 gives 7-10 and is transformed into 11 by incorporation of the solvent.On 1π,π*-excitation (λ λ≥347 nm; benzene-d6) (E)-2 is isomerized into (Z)-2, which is converted into the isomers 3 and 4 by further irradiation.1π,π*-Excitation (λ = 254 nm; acetonitrile) of 4 gives 6 and (E)-9, whereas UV.-irradiation (λ = 254 nm; acetonitrile-d3) of 5 yields (E)-7 and 8.On 1π,π*-excitation (λ = 254 nm; acetonitrile) of (E/Z)-12 the compounds (E)-14 and (E)-15 are obtained.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640123
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  • 7
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen. 121. Mitteilung. Zur Photochemie von ε,ζ-Methano-α,γ-dienonen und 7,8-Methano-1,3,5-trienenHerrn Prof. George H. Büchi zum 60. Geburtstag mit den besten Wünschen gewidmet (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1235-1246 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of ε,ζ-Methano-α,γ-dienones and 7,8-Methano-1,3,5-trienesIrradiation of the δ-cyclopropyl-dienone (E)-6 (λ ≥ 347 nm) gives (Z)-6, 10 (1,5-sigmatropic H-shift), (E/Z)-9 (electrocyclic process involving C(ε), C(ζ)-cleavage) and 11 (ring opening).The corresponding 6-cyclopropyl-triene (E)-7 gives on singlet excitation (δ 〉 280 nm) 14 (1,5-sigmatropic H-shift) and, to a smaller extent, the bicyclo [3.2.0] heptenyl-dienes (E/Z)-13. However, on triplet excitation (λ ≥ 347 nm, benzophenone) (E)-7 gives (E/Z)-13 as the main products. On both 1π,π*- and 3π,π*-excitation, (Z)-7 and 15 are formed in small amounts.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640502
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  • 8
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen. 106. Mitteilung. Zur Photochemie tetraalkylsubstituierter γ-Keto-olefineIn memoriam Robert B. Woodward (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 154-190 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Photochemistry of Tetraalkyl Substituted γ-Keto-olefinesThe photochemistry of 7,8-dihydro-β-ionone (1) in solution is shown to depend on temperature, polarity and viscosity of the solvent. UV. irradiation (λ ≥ 245 nm) in pentane at +25° converts 1 to the isomeric ethers 3 (16%), 5A (48%) and 5B (22%), whereas at -65° 7,8-dihydro-γ-ionone (26) is obtained in 12% yield together with 13% of 3, 12% of 5A and 9% of 5B. The 1n,π*-excitation of 1 in acetonitrile gives similar results. In the more viscous 1,2,3-triacetoxypropane the photoisomerization 1 → 26 takes place even at + 60° (10% yield, cf. 40% at -15°). In alcoholic solvents, however, no formation of 26 is detected, but the hitherto unknown [2+2]-photocycloaddition 1 → 11 can be observed (4% at -7°, 15% at -65S° in 2-propanol). An intermediate e may be involved (Scheme 14). In addition to the photoreactions 1 → 3, 5A, 5B and 11 the isomerization of 1 to the novel spirocyclic ketone 28 takes place in alcoholic solvents only.Photoisomerization 1 → 3 is presumably a photo-ene process involving a stereoselective intramolecular H-transfer. This type of photoisomerization is restricted to cyclic γ-keto-olefines. The tetraalkylated acyclic γ-keto-olefines 14 and 15 photoisomerize exclusively by [2+2]-cycloaddition, independent of the solvent.On 1n,π*-excitation the δ,∊-unsaturated bicyclic ketone 44 undergoes Norrish-Type-II photofragmentation to the diene 45 or isomerizes to the γ, ∊-unsaturated ketone 17. Competition between these two reactions is strongly temperature dependent: photolysis in pentane at -72° yields quantitatively 45, whereas at + 35° only 30% of 45 and 68% of 17 are obtained.UV. irradiation of the novel spirocyclic ketone 28 gives as primary photoproduct the isomeric aldehyde 29, and in a secondary photoreaction the isomeric oxetanes 30A and 30B. Experiments with deuteriated substrates show that the isomerization of type 28 → 29 is stereocontrolled.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630116
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  • 9
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen 114. Mitteilung [1]. Zur Photochemie cyclischer Acetale vom 1,3-Dioxa-4,6-cycloheptadien-Typus (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 2221-2229 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of Cyclic Acetals of the 1,3-Dioxa-4,6-cycloheptadiene TypeUV.-irradiation (λ=254 nm) of 3 gives the isomers (E)-5 (4%), (Z)-5 (60%) and 6 (3%). On triplet sensitization (acetone; λ ≥ 280 nm) 3 is converted to (E)-5 (3%), (Z)-5 (7%) and 7 (9%). - The 1π,π*-excitation (λ=254 nm) of 4 yields the isomers 2 (9%), 8 (10%), 9 (34%), 10 (20%) and 11 (3%). On thermolysis (200°) 4 gives 10 (87%) by a Claisen-rearrangement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630812
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  • 10
    Electronic Resource
    Electronic Resource
    Photochemische Reaktionen 115. Mitteilung [1]. Zur Photochemie konjugierter γ,δ-Epoxyenone: Der Einfluss eines Hydroxylsubstituenten in ∊-StellungMit den besten Wünschen Herrn Dr. Willy G. Stoll zum 70. Geburtstag zugeeignet (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 2230-2257 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of Conjugated γ,δ-Epoxyenones: The Influence of a Hydroxy Substituent in ∊-PositionOn 1n, π*- or 1π,π*-excitation (λ ≥ 347 or λ=254 nm), the ε-hydroxy-γ;,δ-epoxyenone 8 undergoes fission of the C(γ)—O bond followed by the cleavage of the C(δ)-C(ε) bond. This hitherto unknown sequence of reactions is evidenced by the structure determination of the new type products 10-17 and 25, including a synthetic proof for 12 and the X-ray analysis of 11 (X-ray data: triclinic P1; a=7,386(2), b=8,904(4), c=9,684(5)Å; α=82,29(4)°, β=74,46(3)°, γ=82,29(3)°; Z=2).The selective 1π,π*-excitation also induces competitive C(γ)-C(δ) bond cleavage to yield the bicyclic acetal 18 and a ketonium-ylide intermediate a, which photochemically forms a carbene b giving the allene 19 and the cyclopropene 20.On 1n,π*-excitation of the acetate 9 the initial C(γ)-O bond fission is, in contrast to the behaviour of the corresponding alcohol 8, followed by a 1,2-methyl shift affording (E/Z)-28 or by a cyclization-autoxidation process yielding the lactone 29.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630813
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