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  • 1
    Electronic Resource
    Electronic Resource
    Novel Potential Enantioselective Phase Transfer Catalysts Based on Lupinine (1998)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 340 (1998), S. 572-575 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ten N-alkylated lupininium derivatives 5-8 were prepared as potential enantioselective phase transfer catalysts. Compounds 5a-d, 6a-d contain four asymmetric centers (including one in the side chain) with known configuration resting on an X-ray structure. Preliminary PT catalytic experiments in several reactions gave high chemical yields but relatively disappointing enantioselectivities.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19983400612
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Unusual reactions between chloroketenes and 1,3,5-tri-tert-butylcyclopentadiene (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1915-1919 
    Details
    ISSN: 0947-3440
    Keywords: Bicyclo[3.2.0]heptenones ; Complex rearrangements ; Cyclopentadiene, acylation ; Formal Diels-Alder reaction, ketene-cyclopentadiene ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of title compound 1 with dichloroketene resulted in a complex rearrangement to 2 when the ketene was generated from Cl3CCOCl/Zn. In contrast, treatment of 1 with the ketene produced from dichloroacetyl chloride/triethylamine gave a bicyclo[3.2.0]heptenone (3) along with acylation product 4. Reaction of monochloroketene with 1 afforded the „normal“ endo-chloro compound 6 which thermally rearranged to the formal Diels-Alder product 7.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199511270
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  • 3
    Electronic Resource
    Electronic Resource
    Stereoselective Alkylation of Sulfoxides and Sulfones Derived from (R)-Cysteine (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1013-1018 
    Details
    ISSN: 0947-3440
    Keywords: Chelate control ; Cysteinol, protected ; Oxazoline sulfones and sulfoxides, chiral ; Alkylation, stereoselective ; Asymmetric synthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (R)-Cysteinol was protected as its oxazoline derivatives 1a-c and oxidized to the sulfoxides 2, 3 and the sulfone 7. These compounds could be alkylated under chelate control to give tertiary and quaternary stereogenic centers in a highly stereoselective manner to yield 4a-c,5, 8a-c, 11 and 12. Starting with the sulfone 7, both configurations at the new chiral center can be constructed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970533
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  • 4
    Electronic Resource
    Electronic Resource
    Tandem Ring Enlargement by Two Carbon Units from the Bicyclo[3.3.0]octane to the Bicyclo[5.5.0]dodecane System (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3135-3138 
    Details
    ISSN: 1434-193X
    Keywords: Bicyclo[5.5.0]dodecatetraene derivatives ; Ring enlargement, 5-membered → 7-membered ; [1,5]-H shift ; Polycycle by twofold Michael addition ; Adducts of enamines and alkynoic esters ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the bis(enamines) 2b and 3bwith acetylenedicarboxylic ester gave stable tetracyclic compounds 4b and 5b. The related compound 3a, however, led to bicyclo[5.5.0]dodecatetraenes 6a, 6b, and 7a/7b directly. 7a/7b are interrelated by a rapid [1,5]-H shift, whereas 6a and 6b do not rearrange. Hydrolysis of 6b yielded the novel cage compound 10 by dual intramolecular Michael addition.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Synthesewettlauf zum Epibatidin, einem neuartigen Naturstoff mit hoher analgetischer Wirkung (1995)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 167-174 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Epibatidine Competition: Synthetic Work on a Novel Natural AnalgeticEpibatidine was isolated in 1992 from a South American poison frog. It has a unique structure among natural products, and its analgetic activity surpasses that of morphine up to 500 fold. Pharmacological interest in epibatidine focusses also on the fact that its mode of action is different from that of morphine. 10 independent syntheses were published in 1993/1994. They are compared here demonstrating the interaction of classical and modern synthetic methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19953370139
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  • 6
    Electronic Resource
    Electronic Resource
    Preparation of diastereomerically pure 9-carboxybicyclo[6.1.0]nonane derivatives (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 303-306 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of cyclooctene (1) with dibromocyanoacetic esters and copper(I) bromide give (8-10) : 1 mixtures of isomers (2, 3), not stereochemically pure compounds as reported by others. The stereochemistry is elucidated by independent synthesis of one diastereomer (3a). Carbenoid addition of alkoxycarbonylmethylene to 1 and 1,5-cyclooctadiene leads also to exo/endo adduct mixtures. Methods are developed to generate diastereomerically pure compounds (exo-7a, exo-8, endo-9, exo-10, endo-10) from these. Endo esters of this series undergo very facile base catalyzed epimerization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19963380161
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