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  • 1
    Electronic Resource
    Electronic Resource
    NMR Spectroscopy of Organolithium Compounds, XV[1]. Two-Dimensional 6Li,1H-NMR Shift Correlation by Multiple Quantum Spectroscopy and Polarization Transfer: New Tools for Structural Research in the Field of Organolithium Compounds (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2747-2751 
    Details
    ISSN: 0009-2940
    Keywords: Polylithium compounds ; NMR, 6Li ; Shift correlation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sizable scalar 6Li,1H spin-spin coupling constants have been observed for the new dilithio compound (Z)-2-lithio-1-(o-lithiophenyl)ethene (3) which allow an assignment of the two non-equivalent 6Li resonance signals measured for the dimer of 3. Two-dimensional 6Li,1H shift correlation experiments based on multiple quantum spectroscopy as well as on polarization transfer are introduced as new tools for structural research in the field of organolithium compounds.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261226
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  • 2
    Electronic Resource
    Electronic Resource
    Polylithiumorganische Verbindungen, XVI. 1,4-Disila[6]radialene: Aktivierungsparameter der Sessel-Twist-Inversion und analytische Enantiomerentrennung der Twist-Konformeren (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 2033-2036 
    Details
    ISSN: 0009-2940
    Keywords: 1,4-Disila[6]radialenes ; [6] Radialenes ; Chair-twist inversion, kinetic measurements of ; Twist conformers, separation of enantiomers of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polylithiumorganic Compounds, XVI. - 1,4-Disila[6]radialenes: Activation. Parameters of the Chair-Twist Inversion and Analytical Separation of the Enantiomers of the Twist ConformersKinetic measurements of the chair-twist inversion of the 1,4-disila[6]radialenes 2 - 4 have been performed at four different temperatures, respectively. The entropies of activation are found to be negative. While the chair conformers of the radialenes are achiral as expected, the enantiomers of the three twist conformers could be separated by HPLC on an optically active stationary phase.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240925
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  • 3
    Electronic Resource
    Electronic Resource
    Versuche zur Umlagerung von Cyclobutyl- in 3-Butenyl-Anionen: Endocyclische Ringöffnung bei der Reaktion von (3,3-Diphenyl-1-vinylcyclobutyl)methylether mit Alkalimetallen - anionisch oder radikalisch? (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 185-192 
    Details
    ISSN: 0009-2940
    Keywords: Ring-chain equilibria of carbanions and radicals / Cyclobutyl anion, stability of / Endocyclic ring opening of cyclobutyl radicals / Ziegler ether cleavage with lithium and sodium / C-C σ-bond cleavage with lithium metal ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempted Rearrangement of Cyclobutyl Anions to 3-Butenyl Anions: Endocyclic Ring Opening upon Reaction of 3.3-Diphenyl-1-vinylcyclobutyl Methyl Ether with Alkali Metals - via Anions or Radicals?The reaction of the title compound 16 with lithium or sodium in THF yields mainly the open-chain E/Z isomeric trianions 31 ⇌ 32 besides the expected cyclobutyl anion 10. The endocyclic ring opening takes place via the radical intermediate 28 primarily yielding a butadiene derivative 29, which is then further reduced. The anion 10 - prepared independently by deprotonation of the corresponding hydrocarbon 18 - does not rearrange. On investigating side reactions it was discovered that 4,4-diphenyl-1-butene derivatives treated with lithium in THF undergo C-C bond cleavage affording diphenyl-methyllithium in good yields.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230131
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  • 4
    Electronic Resource
    Electronic Resource
    Studien zur enantio- und diastereoselektiven α-Metallierung prochiraler Sulfoxide mit (+)-Menthyllithium (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 2489-2498 
    Details
    ISSN: 0009-2940
    Keywords: (+)-Menthyllithium, stereoselective metallation with ; Prochiral sulfoxides, enantio- and diastereoselective α-deprotonation of ; 2-Bornyllithium, content of isobornyllithium in ; Racemization, mechanism by intermolecular transmetallation ; e.e., temperature dependence of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantio- and Diastereoselective α-Metallation of Prochiral Sulfoxides by (+)-MenthyllithiumSix out of ten prochiral dialkyl sulfoxides 3 with diastereotopic α methylene protons were stereoselectively metallated by (+)-menthyllithium (11) to yield two diastereomeric pairs of enriched enantiomers 29 after the reaction with benzophenone. The maximum e.e. was 40%. Dicyclohexyl sulfoxide (3c) was deprotonated enantioselectively with an e.e. of 30%. 2-Bornyllithium (21) was unsuccessful as a chiral base and was shown for the first time to contain 4% of isobornyllithium (22). The reactions were performed in pentane at - 80°C; in diethyl ether and THF the e.e.'s were only slightly higher, and at higher temperatures the selectivity was rapidly decreasing. It was shown that racemization takes place by an intermolecular transmetallation reaction. The structure of 29f [n = 3] was elucidated by an X-ray analysis.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911241120
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  • 5
    Electronic Resource
    Electronic Resource
    Polylithiumorganic Compounds, XIIII. “Phospha[3]radialenes”  -  Reactive Intermediates in the Synthesis of “Phospha[6]radialenes” (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 933-938 
    Details
    ISSN: 0009-2940
    Keywords: Phospha[3]radialenes ; Alkenylidenephosphiranes ; tautomerism of ; Phosphiranes ; quaternization of ; Phosphiranes ; ring opening to bis(alkylchlorophosphino)butadienes ; Phospha[6]radialenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the dilithiobutadiene 1 with various dichloroorganylphosphanes in diethyl ether at -80°C leads to the formation of the novel phosphiranes 5a-e and 6a, 6c-e in up to 86% yield. A thermal isomerization of the alkenylidenephosphiranes 6 leads to the complete formation of the corresponding “phospha[3]radialenes” 5. Quaternization of the latter gives the cyclic phosphonium salts 8b-d, on addition of iodomethane, while methylation of 5a leads to the acyclic 9a. The phosphiranes 5c-e and 6c-e are converted into the bis- (alkylchlorophosphino)butadienes 10c-e by addition of the corresponding dichloroorganylphosphane at room temperature, whereas 5a,b and 6a are quite unreactive. The interaction of 10e with 1 gives the “phospha[6]radialene” 12e, a formal dimer of 5e. The isolated 1,4-diphosphorinane 12e exists in a rigid trans-chair conformation as revealed by its NMR spectra.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240438
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