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  • Organic Chemistry  (5)
  • Norartemeseol, rac-  (1)
  • 1
    Digitale Medien
    Digitale Medien
    (Diacetoxyiodo)benzene DIB - a Multitalented Oxidant in Organic Synthesis (1998)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 340 (1998), S. 184-186 
    Details
    ISSN: 0941-1216
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prac.19983400215
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  • 2
    Digitale Medien
    Digitale Medien
    Product Analysis in the Iodine(III)-Promoted Oxidation of Carbohydrate-Derived Cyclic Enol Ethers: A Mechanistic Study (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2125-2132 
    Details
    ISSN: 0947-3440
    Schlagwort(e): Carbohydrates ; Glycals ; Hypervalent iodine ; Mechanism ; Ring-contraction ; Tetrahydrofurans ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A study on the mechanism of the well-documented hypervalent iodine-mediated allylic oxidation of glycals leading to 2,3-dihydro-4H-pyran-4-ones is presented. Notable features are the isolation of ring-contracted by-products 6 and 7, which are produced upon oxidation of per-O-benzylated glycal 4, as well as the characterization of carbohydrate-derived tetrahydrofurfurals 12a and 13a, which are formed by the conformation-dependent oxidation of glycals 9a and 10b. In addition, the iodine(III)-mediated oxidation process has been studied by in situ NMR spectroscopy of lyxo-configured glycals 14a,b. Intermediate alkylphenyliodonium species 19b,d and 2-enoyranosides 16a and 20a have been characterized by their NMR signals. These data support a plausible mechanism that is initiated by electrophilic attack of the iodine(III) reagent on the electron-rich enol ether double bond of the glycal. This is followed by the breaking of a bond β,γ-positioned in relation to the carbohydrate-bound iodine and subsequent reductive elimination of iodobenzene. Thus, depending on the glycals employed, a number of diverse oxidation products may be formed.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.199719971015
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  • 3
    Digitale Medien
    Digitale Medien
    3,4-bis(O-tert-butyldimethylsilyl)-6-O-tosyl-D-glucal: A probe for the mechanism of the iodine(III)-promoted allylic oxidation of glycals (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 2053-2056 
    Details
    ISSN: 0947-3440
    Schlagwort(e): 2,3-Anhydropyranose ; Glycal ; Hypervalent iodine ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of 3,4-bis(O-tert-butyldimethylsilyl)-6-O-tosyl-D-glucal 4 with the Koser reagent [PhI(OH)OTs] unexpectedly afforded tetrahydrofurfural 6 as well as 2,3-anhydropyranose 7 as major products. This unprecedented, stereoselective transformation helps to gain further insight into the mechanism of the well-documented hypervalent iodine-promoted allylic oxidation of cyclic enol ethers. A novel chemoenzymatic method for the preparation of glucal 4 in high yield is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.1995199511289
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  • 4
    Digitale Medien
    Digitale Medien
    Synthesis of Functionalized Cyclopentanes, Cyclohexanes and Cycloheptanes by a Silicon-Induced Domino Reaction (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1811-1821 
    Details
    ISSN: 0947-3440
    Schlagwort(e): Domino reaction ; Functionalized cyclopentanes, -hexanes and -heptanes ; Tetrahydrofurans ; Oxetanes ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1,3-Functionalized cyclopentanes, -hexanes and -heptanes are obtained by addition of lithiated silyldithioacetals 7 to epoxyhomoallyl tosylates 4-6, The reaction involves a cascade of epoxide ring opening, of Brook 1,4-rearrangement and tosylate substitution. The method is particularly suitable for the preparation of cyclopentanes, whereas cyclohexanes and -heptanes are formed in yields only up to 49%. Use of enantiomerically pure epoxides provides optically active cyclopentanes (S)-10b, d, 11a as well as oxetanes (S)-14a, b. Hydrolysis of the dithioacetal function leads to the corresponding ketones 12, Cyclization of epoxide 24b gives an anellated cyclopentane 26, the configuration of which was established by X-ray structural analysis of dinitrobenzoate 27. Use of epoxide 29b provides the anellated tetrahydrofuran 30.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.199619961115
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  • 5
    Digitale Medien
    Digitale Medien
    Synthese von rac-Norartemeseol (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 933-936 
    Details
    ISSN: 0170-2041
    Schlagwort(e): Norartemeseol, rac- ; Allyl anion, hetero-substituted ; Oxiranes, ring-opening ; Tetrahydrofuran, substituted ; Cyclopropane, vinyl- ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of rac-NorartemeseolThe synthesis of the terpenoid rac-norartemesol (1b) is accomplished using epoxide ring-opening reactions as key steps. Thus, addition of the thio-substituted allyl anion 2b to ethylene oxide followed by proton-induced cyclisation provides the tetrahydrofuran 4a. The oxirane 6, which is formed by simple functional group interconversion, is opened by the diethylaluminium salt 10 of a propargylsilane. After catalytic hydrogenation and tosylation, fluoride-induced cyclisation of the allylsilane 13 gives the target molecule 1b.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.1991199101159
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