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  • Cuprates  (1)
  • NMR, coupling, constants, HH, CH, CLi  (1)
  • 1
    Electronic Resource
    Electronic Resource
    (EIZ)-Equilibria, 19 Part 18: Ref.[19].  -  [*I X-ray structural analyses. Dimeric α-Lithio-2,6-dimethylstyreneDedicated to Prof. Joseph Klein on the occasion of his 80th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 585-592 
    Details
    ISSN: 0009-2940
    Keywords: Aggregations ; Complex, tert-butyl methyl ether ; diastereotopomerization, (EIZ) ; NMR, coupling, constants, HH, CH, CLi ; NMR, Lithiation shifts ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Improved preparations of 2,6-dimethylstyrene (5) and its α-bromo derivative (10) are described. The Br/Li exchange reaction of 10 provides single crystals of the title compounds 11 or 12, which were characterized as disolvated dimers by X-ray analyses. A similar dimer persists in diethyl ether, tert-butyl methyl ether, and toluene at all accessible temperatures, with significant lithiation NMR shifts (relative to 5) partially due to charge delocalization from the sp2-carbanionic center. Some NMR coupling constants are typical of the dimeric aggregate. The configurational (E,Z) lability is quantified in toluene solution.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300509
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  • 2
    Electronic Resource
    Electronic Resource
    Sterically Congested Molecules, 11. The 2,6-Diisopropylphenyl Substituent at C=C and C=N Groups (1994)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 433-438 
    Details
    ISSN: 0170-2041
    Keywords: Aryl group, rotation ; Cuprates ; Diastereotopomerization ; Hydrazones ; Styrene derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two series of new compounds with sterically shielded, sp2-hybridized C-α atoms are prepared from bromo(chloro)-2,6-diisopropylbenzene. The α-(2,6-diisopropylphenyl) substituent common to all of them is used as an NMR-spectroscopic indicator for the ease of aryl-α single-bond rotation. The corresponding ΔG≠ values are 〉23.8 kcal/mol with methyl or bromine as additional α substituents at a C=C bond, but 〈8.5 kcal/mol with α-H. The analogous 2,6-diisopropylacetophenone imine has ΔG* = 18.0 kcal/mol while the N-substituted imines prefer the (Z) conformations with ΔG≠ 〉 23.3 kcal/mol, and ΔG≠ ≈ 31.5 kcal/mol for the (Z)-hydrazone. Comparisons of these data with reaction conditions show that chemical transformations are not seriously impeded unless they depend on reagent attack at a π face of the C-α atom in a C=C or C=N group which rotates slowly about the bond to 2,6-diisopropylphenyl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199419940417
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    Paper (German National Licenses)
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