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  • 1
    Electronic Resource
    Electronic Resource
    Convergent Synthesis of Columnar Twins and Tetramers from Triphenylene Building Blocks - The First Example of a Columnar Spiro-Twin (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2499-2506 
    Details
    ISSN: 1434-193X
    Keywords: Liquid crystals ; Discotic twins ; Discotic oligomers ; Spiro compounds ; Triphenylene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel spiro-twins 3a-f were prepared in three steps by one-pot oxidative coupling of guaiacol (9) and 1,2-dialkoxybenzenes 10a-f, followed by demethylation of the triphenylene 11 and subsequent etherification with the tetrabromide 6. A related strategy gave the tetramers 7a-f in two steps. Whereas derivatives 3a,b and 7a,b with pentyloxy and hexyloxy chains showed isotropic melting behavior, compounds 3c-f and 7c-f with longer alkyl chains displayed columnar mesophases. DSC, polarizing microscopy, X-ray diffraction and molecular modeling studies were used to further characterize the type of mesophase. For the spiro-twin 3 either a rectangular or a hexagonal columnar phase were conceivable. In case of 7f a hexagonal columnar mesophase was assigned.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Diastereoselective Synthesis of 1-Hydroxy-Substituted Benzo[b]quinolidines and 11-Hydroxy-Substituted Azepino[1,2-b]isoquinolines via Hetero-Ene Cyclization (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 533-540 
    Details
    ISSN: 0947-3440
    Keywords: Ene reaction ; Benzo[b]quinolidines ; Azepino[1,2-b]isoquinolines ; Lewis acid catalysis ; Nitrogen heterocycles ; Cyclizations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (L)-Phenylalanine 4 can be converted to N-(4-methyl-3-pentenyl)tetrahydrosisoquinoline-3-carbaldehyde 10 and the corresponding homologous aldehyde 19 in 4 and 5 steps, respectively, by employing the Pictet-Spengler reaction as the key step. After Lewis acid catalyzed cyclization of 10 and 19 the cis-configured 1-hydroxybenzo[b]quinolizidine 21a and 11-hydroxyazepino[1,2-b]isoquinoline 22a were obtained with high diastereoselectivities. Compound 21a, which was characterized by X-ray structure analysis, displays a fishbone pattern of endless zig-zag chains connected via intermolecular hydrogen bonds in the solid state.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970314
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    New Synthetic Pathways to Nitrogen Heterocycles (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1-11 
    Details
    ISSN: 0947-3440
    Keywords: Nitrogen heterocycles ; Imines ; Hetero-Diels-Alder reaction ; Hetero-ene reaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel Lewis acid-catalyzed cyclizations of N-arylimines and N-benzylimines derived from amino acids and terpenes allow the diastereoselective preparation of octahydroacridines, indolizino[3,4-b]quinolines, indolizidines, quinolizidines and piperidines. Although these two types of reactions can be classified as formal hetero-Diels-Alder and hetero-ene reactions respectively, both proceed stepwise via cationic intermediates, which allow stereochemical control via chelate complexes. Stereochemical and mechanistical studies are described briefly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970104
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    Paper (German National Licenses)
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