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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and Reductive Elimination Reactions of Aryl Thioglycosides (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 1211-1217 
    Details
    ISSN: 0170-2041
    Keywords: Thioglycosides, aryl ; Glycals ; Diphenyl disulfide ; Phosphanes, trialkyl ; Disulfides ; Carbohydrates ; Potassium-graphite laminate ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of the sugar hemiacetals 1, 5, 7, 10, 12 and 14 with ArSSAr (Ar = phenyl, 2-pyridyl, 2-benzothiazolyl) and trialkylphosphanes affords in an SN2 process the corresponding aryl thioglycosides 3, 6, 8, 9, 11, 13, 15 and 16 in good to excellent yields. The reaction can be performed in a variety of solvents of greatly different polarity and avoids the use of free thiols and Lewis acid catalysts. The promoting phosphane has to carry at least two alkyl groups, with R3P (R = short, unbranched alkyl group) being best suited in terms of yield and reaction rate. In contrast, triphenylphosphane and phosphites are inactive. The reaction is compatible with a variety of functional groups and distinguishes between the anomeric center and other free hydroxyl groups in the substrates. Thus, thioglycosides from partially protected or unprotected sugars can be readily obtained. Treatment of phenyl thioglycosides 13a and 3a with potassium-graphite laminate (C8K) in THF affords the corresponding pyranoid or furanoid glycals 17 and 18 by reductive elimination.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301196
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  • 2
    Electronic Resource
    Electronic Resource
    Chemistry of and with Highly Reactive Metals (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 32 (1993), S. 164-189 
    Details
    ISSN: 0570-0833
    Keywords: Metals ; Reactivity ; Activation ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Today, the synthetic chemist has a large repertoire of metal activation methods at his disposal. After a first breakthrough was made at the beginning of the seventies with the introduction of the Rieke metals, a series of further, in part more efficient methods were describes, based on which not only classical metal-induced reactions could be substantially improved but also completely new reactions could be discovered. In this article the individual activation methods are discussed and compared as far as is possible using the currently available data. Especially noteworthy are the metal-graphite combinations because of their unsurpassed reactivity and concomitant easy preparation and manipulation. As shown by numerous applications of these reagents on polyfunctional substrates, particularly natural products, high reactivity of the metal and excellent selectivity are by no means precluded. Besides the purely preparative aspects also insights gained so far into the general principles and limits of metal activation are outlined, and attempts at determining the morphology of highly dispersed systems are reported.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199301641
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    Paper (German National Licenses)
    Fulltext
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