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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of Bimacrocyclic, Monomacrocyclic, and Nonmacrocyclic Bis(amidomethyl)pyridines as Catalysts in the Base-Catalyzed Addition of Alcohols to Ketenes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 847-854 
    Details
    ISSN: 1434-193X
    Keywords: Ketene ; Homogeneous catalysis ; Hydrogen bonds ; Molecular recognition ; General base ; Macrocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Nineteen new bimacrocyclic, monomacrocyclic, and nonmacrocyclic pyridines 1-6 bearing amide functions have been synthesized and utilized in base-catalyzed additions of alcohols (ethanol, 2-propanol) and polyols [propane-1,2-diol (11a), butane-1,3-diol (12a), methyl 4,6-O-benzylidene-α-D-glucopyranoside (13a)] to diphenylketene. Compounds 4c, 4d and 1b proved to be efficient and selective catalysts; 4c and 4d exhibited better results with 11a and 12a, and 1b was the best catalyst for selective 2-O-acylation of 13a.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Stereoselective Total Synthesis of a Novel D-Homosteroid by a Twofold Heck Reaction (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1827-1830 
    Details
    ISSN: 1434-193X
    Keywords: C-C coupling ; Homosteroids ; Palladium ; Steroids ; Total synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The D-homosteroid 1 was synthesized by two successive Heck reactions starting from enantiopure 3 and the bromoarene 2 containing a (Z)-bromovinyl group. The first intermolecular Pd-catalyzed reaction leads to 6 in a highly regio- and diastereoselective way which forms 1 with an unusual cis-junction of the rings B and C by a second intramolecular Heck reaction.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Concave Pyridines for Selective Acylations of Polyols (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1077-1084 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Catalysis ; General base ; Macrocycles ; Molecular recognition ; Hydrogen bond ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selectivity enhancements in the base-catalyzed acylation of polyols (1,2- or 1,3-alkanediol, partially protected glucoside) have been found with (bi)macrocyclic pyridines 2 and 9 as catalysts. The different selectivities obtained for concave pyridines of varying ring sizes (1 vs. 2) are probably caused by their different geometries as a number of X-ray analyses (1a, 1b, 2a, 2b, 2e, 9) indicate. The methyl glucoside 7 can selectively be acylated in 2-position.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Concave Reagents, 21Part 20: Ref.[1].. Selective Acylations of Primary and Secondary Alcohols by Ketenes (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 2099-2105 
    Details
    ISSN: 0947-3440
    Keywords: Bimacrocycle ; Base catalysis ; Hydrogen bond ; Molecular recognition ; Pyridine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Concave pyridines 1 were used to catalyze the addition of primary and secondary alcohols to ketenes 4, and the kinetic data of these catalyses were determined. In inter- and intramolecular competitions the use of 1e-g led to improved selectivities for the acylation of primary alcohols in comparison with secondary alcohols. All primary alcohols react at comparable rates. Observed rate constants were correlated with Taft's Es values. The starting materials and products were fully characterized.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961223
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