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  • 1
    Electronic Resource
    Electronic Resource
    Periselective intramolecular cycloaddition of allene-1,3-dicarboxylates. Unusual structural feature of [2 + 2] cycloadducts (1988)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 110 (1988), S. 1232-1238 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00212a036
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  • 2
    Electronic Resource
    Electronic Resource
    Strain, orbital interaction, and conformation of propella[34]prismane and its precursor diolefin (1990)
    Springer
    Structural chemistry 1 (1990), S. 333-344 
    Details
    ISSN: 1572-9001
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Factors that influence the intramolecular [π2+π2] photochemical ring closure reaction of multiply bridgedsyn-tricyclo[4.2.0.02.5]octa-3,7-diene (2) leading to propella[34]prismane (1) are analyzed. The unfavorable, large increase in strain (89 kcal mol−1) calculated for this reaction is overcome by the favorable ordering of frontier molecular orbitals, which is caused primarily by bridging of the juxtaposed double bonds with trimethylene chains in2. This conclusion is based on detailed analysis of the frontier molecular orbitals (FMO) of cycloocta-1,5-diene (6), cyclodeca-1,6-diene (7), and tricyclo-[4.2.0.02.5]octa-3, 7-diene (3), bridged with alkylene groups of various lengths, in terms of Paddon-Row's theory of through-bond interaction by the use of AM1 semiempirical MO method. In addition to the π-orbital interaction through an even number of C-C bonds, the double-bond-double-bond distance is recognized to be an important factor for the ordering of FMOs. It is suggested that reduction of this distance in6 by only a few tenths of an Ångstrom will change the FMO ordering and allow the intramolecular [π2+π2] cycloaddition to proceed. Potential energy calculations by MM2 indicate that the trimethylene bridges in1 and2 are so flexible that they appear flat on the NMR time scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01374480
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  • 3
    Electronic Resource
    Electronic Resource
    Energy-minimum structure of the hydrocarbon portion of [45] (1,2,3,4,5)ferrocenophane (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 602-610 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to assist in the interpretation of the D5h molecular structure of [45] (1,2,3,4,5)ferrocenophane (1) obtained from x-ray crystallographic analysis, a hypothetical hydrocarbon C30H40 (2) was derived from 1 by removing the iron atom and subjected to geometry optimization by molecular mechanics. A stable D5 conformer was found for 2, which has a g+ g- g+ helical bridge conformation and a ring-ring distance almost identical with that in 1 and ferrocene itself. Optimization of a perhydrogenated hydrocarbon model gave a highly strained C1 structure.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610020803
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular mechanics of bridged ferrocene derivatives: Conformational energy surfaces of [3]-, [4]- and [45] ferrocenophanes (1992)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 5 (1992), S. 382-394 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A molecular mechanical model is presented which allows computational interpretation of stereodynamics in ferrocenophanes by using a simple form of bending potential for angles involving the central iron atom and extended to carbon atoms of different cyclopentadienyl rings. Potential energy surfaces of [3] -, [4] - and [45] ferrocenophanes were studied in detail. For [3] ferrocenophane, the calculated energy barrier of the bridge reversal process agrees well with the experimental value. The previous interpretation of a rigid bridge in [4] ferrocenophane is questioned on the basis of the calculated low barriers. The predominance of experimentally indistinguishable enantiomeric pairs may be responsible for the misinterpretation. [45] Ferrocenophane is estimated to interconvert into D5-symmetric global energy minima over barriers of 13-15 kcal mol-1 through one-by-one flipping of five tetramethylene bridges.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610050703
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  • 5
    Electronic Resource
    Electronic Resource
    A Conformational Study of [3.3](2,6)Pyridinophane by the Dynamic NMR Method and X-ray Structural Analysis (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1645-1649 
    Details
    ISSN: 0947-3440
    Keywords: [3.3](2,6)Pyridinophanes ; Conformational analysis ; Hydrogen bond ; Dynamic NMR spectroscopy ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variable-temperature 1H-NMR study and X-ray structural analysis show that the most stable conformational isomer of [3.3](2,6)pyridinophane 2 is the syn(boat-boat) conformer, and the relative stability order of the three stable conformers is syn(boat-boat) 〉 syn(chair-boat) 〉 syn(chair-chair). This is in sharp contrast to the relative stability order of the parent [3.3]metacyclophane 1: syn(chair-chair) 〉 syn(chair-boat) 〉 syn(boat-boat). The high stability of the syn(boat-boat) conformer 2c is primarily attributed to weak attractive interactions via intramolecular hydrogen bonds between nitrogen lone pairs (N-1, N-2) and the axial hydrogen atoms (2A-H, 11A-H) on the central carbon atoms of the bridges, as suggested by their short transannular distances (2.50 Å).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961023
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