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  • 1
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Helical Hydrocarbons, VIII. Enantiomer Separation, Circular Dichroism, Racemization, and X-Ray Analysis of Benzo[2.2]-metacyclophaneThe title compound 1 was separated into the enantiomers by chromatography on cellulose triacetate: (-)-1 exhibits an enantiomeric purity of 100% with [α]36520 = -3210 ± 135 (acetone). A racemization barrier ΔG≠ = 125 kJ/mol is found by means of a kinetic study. The helicity of the molecule is demonstrated through these results as well as through an X-ray analysis, which is also described.
    Notes: Die Titelverbindung 1 wird chromatographisch an Cellulosetriacetat in die Enantiomeren getrennt: (-)-1 hat mit 100% Enantiomerenreinheit einen Drehwert von [α]36520 = -3210 ± 135 (Aceton). Für die Racemisierung wird kinetisch eine Barriere ΔG≠ = 125 kJ/mol ermittelt. Der helicale Molekülbau ist hiermit und durch die Röntgenstrukturanalyse gesichert, die gleichfalls beschrieben wird.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 1363-1366 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Helical Hydrocarbons, VI. Benzo[2.2]metaparacyclophane, a Conformationally Flexible HelixThe target molecule 2 is synthesized for the first time and the dynamic stereochemistry of 2 as well as of the sulfide 10, enlarged by one ring atom, is investigated by NMR spectroscopy: Compared with [2.2]metaparacyclophane (3), the benzo compound 2 is somewhat more conformationally flexible (ΔGc± = 76 kJ/mol). The barriers of the ring inversions for the thia compound 10 (ΔGc± = 37 kJ/mol) and the sulfone 11 are much lower.
    Notes: Die dynamische Stereochemie des erstmals synthetisierten Zielmoleküls 2 und des um ein Ringatom erweiterten Sulfids 10 wird NMR-spektroskopisch untersucht: Im Vergleich zum [2.2]Metaparacyclophan (3) ist die Benzo-Verbindung 2 konformativ flexibler (Ringinversionsbarriere ΔGc± = 76 kJ/mol). Die Barrieren der Thia-Verbindung 10 (ΔGc± = 37 kJ/mol) und des Sulfons 11 liegen wesentlich tiefer.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 2533-2539 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Helical Hydrocarbons, VII. Clamped Quaterphenyl HydrocarbonsThe new many-membered hydrocarbons 1-4 are synthesized starting with 3-ethoxycyclohexenone; 5 is available through Ullmann-coupling. DNMR studies show that these molecular skeletons with the exception of 4 are comparatively rigid helices. The larger sulfide rings 6a-11a exhibit lower ring inversion barriers.
    Notes: Die neuen vielgliedrigen Kohlenwasserstoffe 1-4 werden ausgehend von 3-Ethoxycyclohexenon synthetisiert; 5 ist über eine Ullmann-Kupplung zugänglich. DNMR-Studien zeigen, daß mit Ausnahme von 4 konformative weitgehend starre, helikale Gerüste vorliegen, während die um ein Schwefelatom ringweiteren Cyclen 6a-11a niedrigere Ringinversionsbarrieren aufweisen.
    Additional Material: 2 Tab.
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