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  • 1
    Electronic Resource
    Electronic Resource
    The Low-Temperature UV/VIS Absorption Spectrum of [14]Annulene (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 679-692 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The UV/VIS absorption spectrum of [14]annulene was measured in 3-methylpentane at room and liquid-N2 temperatures and interpreted by the CNDO/S-CI method. This comparison between experiment and theory supports a structure with π-bond delocalization for this molecule.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780315
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  • 2
    Electronic Resource
    Electronic Resource
    Annulene, 28. Synthese von Fluor[18]annulen und 1,2-Dihalogen[18]annulenen sowie Versuche zur Darstellung von 1,2-Diaza[16]annulenen (1978)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1978 (1978), S. 1368-1378 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Annulenes, 28.  -  Synthesis of Fluoro[18]annulene and 1,2-Dihalo[18]annulenes and Attempted Synthesis of 1,2-Diaza[16]annulenesThe dimer 1 of cyclooctatetraene and 1,1-difluoroethylenes 2a, 2b yield, inter alia, the cycloadducts 3a, 3b. The compound 3c is readily accessible from 3a and (Bu)3SnH. The cycloadducts 3a-3c dehalogenated to 6a-6c, photolysis of which affords fluoro-, 1-chloro-2-fluoro- and 1,2-difluoro[18]annulene (7c, 7a and 7b, respectively). The 1H-NMR spectroscopic behavior of the latter compounds is discussed.  -  The strained double bond of the four-membered ring of 8 reacts with tetrazine 9 to give 11-13. The pyridazine derivative 10 is postulated as an intermediate in the reaction. Only 10  -  and not one of the secondary products 11-13  -  could be a potential precursor of a 1,2-diaza[16]annulene.
    Notes: Aus dimerem Cyclooctatraen 1 und den 1,1-Difluorethylenen 2a, 2b bilden sich unter anderem die Cycloaddukte 3a, 3b. Aus 3a ist mit (Bu)3SnH 3c zugänglich. Die Verbindungen 3a-3c lassen sich zu 6a-6c dehalogenieren. Unter der Einwirkung von UV-Licht entstehen daraus Fluor-, 1-Chlor-2-fluor- und 1,2-Difluor[18]annulen (7c, 7a bzw. 7b), deren charakteristisches 1H-NMR-spektroskopisches Verhalten beschrieben wird.  -  Die gespannte Vierringdoppelbindung in 8 reagiert mit dem Tetrazin 9. Es entstehen 11-13. Das Pyridazinderivat 10 wird als Zwischenstufe postuliert. Nur 10  -  nicht aber eines der Folgeprodukte 11-13  -  wäre ein potentieller Vorläufer eines 1,2-Diaza[16]annulens.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197819780903
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of 13C- and 1H-Magnetic Resonance Spectroscopy as Techniques for the Quantitative Investigation of Dynamic Processes. The cope rearrangement in bullvalene (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 1415-1433 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potential advantages of 13C-(1H-noise decoupled) spectroscopy (in the Fourier transform mode) over 1H-spectroscopy for the quantitative investigation of molecular dynamic process is discussed. The Cope rearrangement in bullvalene, an example of complex exchange of spins over different magnetic sites, has been studied by both kinds of spectroscopy as a test.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570518
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  • 4
    Electronic Resource
    Electronic Resource
    The Stabilization Energy of [18] Annulene. A thermochemical determination (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 2276-2288 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal rearrangement of [18]annulene in solution gives benzene and 1,2-benzo-1,3,7-cyclooctatriene. This reaction has been investigated using a differential scanning calorimeter and the associated enthalpy change has been measured. The enthalpy of the reaction (in the gase phase at 298°K) is \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta {\rm H}_{\rm r} \left({{\rm g},\,298^ \circ } \right) = - 50.7 \pm 5\,{\rm kcal mol}^{{\rm - 1}} $$\end{document} From this value and the enthalpies of formation of the reaction products, the enthalpy of formation of [18]annulene is obtained: \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta {\rm H}_{\rm f} \,^ \circ \left({{\rm 1,}\,{\rm g},\,298^ \circ } \right) = 124 \pm 5.5\,{\rm kcal mol}^{{\rm - 1}} $$\end{document} The stabilization energy of [18]annulene, defined as the difference between the enthalpy of formation of the hypothetical Kékulé [18]annulene (with single and double bonds of normal lengths) and the heat of formation of the real molecule is then \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta {\rm H}_{{\rm stab}{\rm .}} \left({\rm 1} \right) = 37 \pm 6\,{\rm kcal mol}^{{\rm - 1}} $$\end{document} a value close to the corresponding quantity found for benzene.The very large stabilization energy of [18]annulen (100 ± 6 kcal mol-1) previously reported in the literature, based on measurements of the heat of combustion, is not correct since the annulene is certainly oxidized in the bomb prior to combustion.The isodynamic conformational mobility of [18]annulene is not incompatible with a stabilization energy of 37 kcal mol-1; the activation enthalpy observed for this process (ΔH≠ = 16.1 kcal mol-1) indicates that the stabilization is not completely destroyed in the transition state.The mechanism of the thermolysis of [18]annulen, investigated by kinetic measurements and by analysis of the shape of the thermograms, is discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570745
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  • 5
    Electronic Resource
    Electronic Resource
    The Dianion of Heptalene (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 2387-2398 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heptalene - a very unstable compound - can be reduced by lithium at -80° into its dianion. 1H- and 13C-NMR. studies indicate that this dianion, contrary to the neutral molecule, has its π-bonds delocalized. The magnetic field induces in this species a large diamagnetic ring current. The dianion of heptalene is thermally very stable, much more so than the neutral compound. All these observations point to an appreciable stabilization energy associated with the 14°-electron system; this stabilization energy is probably large enough to impose a planar geometry to this dianion.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570811
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  • 6
    Electronic Resource
    Electronic Resource
    π-Bond Configurations, Conformations, and Dynamic Behaviour of Benzo[c]octalene and Dibenzo[c,j]octalene (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 2411-2425 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The π-bond configurations, the conformations, and the dynamic behaviour of dibenzo [c,j]octalene (2) and of benzo [c]octalene (3) have been investigated by 13C-NMR. spectroscopy at different temperatures. Dibenzooctalene was found to present π-bond fixation in the octalene unit as in 2b; with this π-bond fixation the molecule is not planar and takes two different conformations which are rapidly interconverted by inversion of one cyclooctatetraene ring. Monobenzooctalene (3) also presents π-bond fixation in the octalene unit but exists as two valence isomers, 3b and 3c. Isomer 3c dominates the dynamic equilibrium. With this π-bond configuration, the molecule is chiral but undergoes several isodynamic processes, namely inversion of the cyclooctatriene and/or of the cyclooctatetraene ring. The valence isomer 3b can have two different conformations which are rapidly interconverted by inversion of one cyclooctatetraene ring. The interconversion 3c ⇌ 3b implies the occurrence of a π-bond shift process; this process affects the 13C-NMR. lineshape above 50°.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630834
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  • 7
    Electronic Resource
    Electronic Resource
    The Low-Temperature UV./VIS. Absorption Spectrum of [18]Annulene (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1885-1893 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The UV./VIS. absorption spectrum of [18]annulene has been remeasured in 3-rnethylpentane at room and at liquid nitrogen (glass) temperature and interpreted by the CNDO/S-CI-method. The confrontation of the experimental electronic transitions with the CNDO/S-CI-calculated ones favors a structure with D6h-symmetry, i.e, a structure with delocalized π-bonds.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650622
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  • 8
    Electronic Resource
    Electronic Resource
    Reductions of Tetrahalo-1,3,5,7-tetramethyl-anti-tricyclo [5.1.0.03,5]octane-2,6-diones. 1,3,5,7-Tetramethyl-anti-tricyclo[5.1.0.03,5]octane-2,6-dioneThe trivial name is anti-bis-homoduroquinone; this nomenclature was used in previous publications (compare [1]).In part from the planned dissertation of R. A. Dyllick-Brenzinger, ETH Zürich. (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 1311-1327 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methoden zur Entfernung von Halogenatomen aus den leicht zugänglichen (Bis-homo-p-chinon)-Derivaten 4,4,8,8-Tetrachlor- (4) und 4,4,8,8-Tetrabrom-1,3,5,7-tetramethyl-anti-tricyclo[5.1.0.03,5]octan-2,6-dion (5) wurden untersucht. Mit LiAlH4 bzw. mit KFeH(CO)4, NaBH3CN oder CrCl2 entstanden Diole bzw. Diketone, in denen ohne Gerüstveränderung verschiedene Halogenatome durch Wasserstoffatome ersetzt worden waren. Die Diole wurden entweder isoliert oder zu den Diketonen aufoxydiert. Von den neun möglichen Dehalogenierungsmustern (Diketone mit unverändertem C-Skelett) liessen sich acht beobachten, sechs davon (8 bis 13) aus 4 und sechs (14 bis 18, 6) aus 5. Nur KFeH(CO)4 entfernte alle vier Halogenatome und dies nur aus dem Tetrabrom-dion 5, wobei das noch unbekannte anti-Isomere von 1,3,5,7-Tetramethyl-tricyclo[5.1.0.03,5]octan-2,6-dion (6) entstand.Die Zuordnung der endo- oder exo-Konfigurationen der nicht-entfernten Halogenatome an den Cyclopropanringen erfolgte auf Grund von 1H-NMR.-Spektraleigenschaften. Als Basisargument diente eine H/13C-Kopplung von 4,5 Hz zwischen exo-H—C(4) und den cis-vicinalen Methyl-Kohlenstoffatomen, welche im 13C-NMR.-Spektrum von 12 beobachtbar ist. Daraus und aus unterschiedlichen Linienbreiten der 1H-NMR.-Signale von endo- und exo-Protonen wurde abgeleitet, dass endo-H immer bei tieferem Feld absorbiert als exo-H. Im Fall von 6 liess sich dies durch geeignete Vergleiche unter Anwendung eines abschirmenden Effektes der angulären Methylgruppen auf exo-H bestätigen. Die Konfigurationen der Hydroxylgruppen in den Diolen 19 bis 22 und 24 bis 27 wurden aufgrund von Symmetrieüberlegungen bestimmt.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19760590434
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  • 9
    Electronic Resource
    Electronic Resource
    Reactions of 1,3,5,7-Tetramethyl-anti-tricyclo[5.1.0.03,5] octane-2,6-diols and their 4,4,8,8-Tetrachloro- and 4,8-Dichloro-Derivatives with Diphosphorus TetraiodideFrom the planned dissertation of R. A. Dyllick-Brenzinger, ETH Zürich. (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 1403-1415 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaktionen von 1,3,5,7-Tetramethyl-anti-tricyclo[5.1.0.03,5]octan-2,6-diolen und deren 4,4,8,8-Tetrachlor- und 4,8-Dichlorderivaten mit DiphosphortetrajodidEs wurden die P2I4-Reaktionen mit 1,3,5,7-Tetramethyl-anti-tricyclo[5.1.0.03,5]-octan-2,6-diolen (3/6), mit dem 4,8-Dichlorderivat 4 und mit den 4,4,8,8-Tetrachlorderivaten 5/7 untersucht. Dabei entstanden die Styrolderivate 9 und 12, die anti-Bishomobenzolderivate 8 und 11, ein Homotropylidenderivat 10, ein Cyclo-octatetraenderivat 13 und ein 9-Oxabicyclo[4.2.1]nona-2,4,7-trienderivat 15. Die Ausbeuten lagen zwischen 1 und 10%. Die Bildung aller dieser Produkte liess sich unter der Annahme der primären Umwandlung einer oder beider Hydroxylgruppen in Abgangsgruppen X oder X und Y (wahrscheinlich X=Y=I) mechanistisch deuten. Die Reaktion der Deschlorderivate 3/6 lieferte nach Substitution beider Hydroxyl-gruppen durch X und Y: (a) unter Abspaltung von HX und HY das Styrolderivat 9 (Schema 2) und (b) unter Abspaltung von XY das Homotropylidenderivat 10 (Schema 3a) und das Bishomobenzolderivat 8 (Schema 3b). Die Reaktion des 4,8-Dichlor-derivates 4 lieferte nach Substitution beider Hydroxylgruppen durch X und Y: (a) unter Abspaltung von HX und HY das Styrolderivat 12 (Schema 2), und (b) unter Abspaltung von XY das Bishomobenzolderivat 11 (Schema 3b). Die Reaktion mit den 4,4,8,8-Tetrachlorderivaten 5/7 lieferte: (a) nach Substitution beider Hydroxyl-gruppen durch X und Y unter Abspaltung von XCl und YCl das Cyclooctatetraen-derivat 13 (Schema 4), und (b) nach Substitution nur einer Hydroxylgruppe durch X unter Abspaltung von XCl und HCl das bicyclische Derivat 15 (Schema 5). Alle diese Reaktionen sind zusätzlich zu den angegebenen Fragmentierungen und Eliminierungen noch teilweise von Umlagerungen des Kohlenstoffgerüstes begleitet.Die thermische Umlagerung von 1,5-Dichlor-2,4,6,8-tetramethyl-cycloocta-1,3,5,7-tetraen (13) in das Styrolderivat 12 wurde in Abhängigkeit der Lösungs-mittelpolarität untersucht und mit der analogen thermischen Umlagerung von Brom-cyclooctatetraen und Chlor-cyclooctatetraen verglichen.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19770600432
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  • 10
    Electronic Resource
    Electronic Resource
    Iterative Least-Squares Lineshape Fitting of 1H-decoupled 13C-DNMR.Spectra (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 258-278 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Iterative least-squares lineshape fitting of 1H-decoupled 13C-DNMR. spectra is advantageously used for the investigation of symmetrical or asymmetrical intramolecular (two-structure) exchange processes. The least-squares procedure adopted allows the following parameters to be either optimized by computer or kept constant (according to experimental conditions): the nuclei populations (taking into account line intensity effects resulting from differences in spin-lattice relaxation times and/or Overhauser enhancements), the corresponding chemical shifts and natural linewidths (characterizing the sites undergoing exchange), the fractional population of one structure (in the case of asymmetrical exchange), one of the chemical rates, the base-line position, and the base-line tilt. The relative sensitivity of the lineshape with respect to the fitted parameters as well as the importance of correlations among these parameters have been investigated and tested with examples. The reliability of the kinetic parameters as obtained by the iterative least-squares lineshape fitting procedure is discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640127
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