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  • 1
    Electronic Resource
    Electronic Resource
    Versatile Synthesis of Enantiomerically Pure 2-Alkoxy-1-Ethynylcyclopropanes and their Application in the Synthesis of Enantiomerically Pure Bicyclo-[3.3.0]oct-1-en-3-onesCyclopropyl Building Blocks for Organic Synthesis, Part 31. Part 30: T. Heiner, S. Michalski, K. Gerke, G. Kuchta, M. Buback, A. de Meijere, Synlett 1995, 335; Part 29: J. L. Coudret, K. Ernst, A. de Meijere, B. Waegell, Synthesis 1994, 920.Dedicated to Professor Manfred Regitz on the occasion of his 60th birthday (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 545-555 
    Details
    ISSN: 0947-6539
    Keywords: alkynes ; asymmetric syntheses ; cyclopropanes ; spiro compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variety of chiral, nonracemic 2-alkoxy-1-alkynylcyclopropanes 7 were synthesized in good to very good yields from enantiomerically pure glycidol derivatives (glycidol tosylate, epichlorohydrin) by boron trifluoride promoted addition of lithium trimethylsilylacetylide followed by protection of the secondary hydroxyl group and finally a diastereoselective γ-elimination. The 2-ethoxy derivative (S,R)-7 b was deprotonated with n-butyllithium, and the resulting 1-lithio-2-ethoxy derivative (S,R)-20 functionalized by treatment with oxygen followed by tosyl chloride. Protodesilylation and catalytic hydrogenation smoothly furnished 1-ethenylcyclopropyl sulfonates, which underwent a clean Pd0-catalyzed SN2′-type substitution with dimethyl propargylsodiummalonate to give the (E)-configurated enyne (R,E)-26 with a methylenecyclopropane end group. A diastereoselective Pauson-Khand reaction completed the sequence to give the enantiomerically pure spirocyclopropaneannelated bicyclo[3.3.0]octane derivative 31.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020514
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  • 2
    Electronic Resource
    Electronic Resource
    Gas-Phase Kinetics of the Thermal 1-Alkoxy-1-vinylcyclopropane to 1-Alkoxy-1-cyclopentene Rearrangement (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 939-945 
    Details
    ISSN: 0009-2940
    Keywords: 1-Vinylcyclopropane ; 1-methoxy- ; 1-ethoxy- ; Vinylcyclopropane ; isomerization ; Gas-phase kinetics ; Ring expansion of 1-alkoxy-1-vinylcyclopropanes ; Diradical intermediates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title studies have been carried out with both 1-vinyl-1-cyclopropyl methyl ether (1-OMe) and 1-vinyl-1-cyclopropyl ethyl ether (1-OEt) in the temperature ranges 274.6-324.5 and 273.6 - 323.0°C, respectively. Both reactions predominantly give the vinylcyclopropane-cyclopentene (VCP-CP) rearrangement products 1-cyclopenten-1-yl methyl ether (2-OMe) and 1-cyclopenten-1-yl ethyl ether (2-OEt). Additionally, 2-OEt eliminates ethene (3) in a consecutive reaction at a lower reaction rate compared with the VCP-CP rearrangement. The rearrangements obey first-order kinetics and have been shown to be homogeneous, pressure-independent reactions with the following Arrhenius equations:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {1 - {\rm OMe:}} {{\rm lg}\left({k/s^{-1}} \right) = \left({13.89 \pm 0.23} \right) - \left({191.30 \pm 2.55{\rm kJ mol}^{-1}} \right)/RT\ln 10} \\\end{array} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {1 - {\rm OMt:}} {{\rm lg}\left({k/s^{-1}} \right) = \left({13.77 \pm 0.01} \right) - \left({188.80 \pm 1.85{\rm kJ mol}^{-1}} \right)/RT\ln 10} \\\end{array} $$\end{document}The Arrhenius parameters represent reliable values for general 1-vinyl-1-cyclopropyl alkyl ether→1-cyclopenten-1-yl-alkyl ether (1-OR→2-OR) rearrangements within a large temperature interval in the gas phase. The results support a mechanism proceeding via a diradical. The stabilizing effect of methoxy substitution is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240439
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    Paper (German National Licenses)
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