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  • 1
    Electronic Resource
    Electronic Resource
    Optisch aktive, aromatische Spirane, 8. Mitt.: Darstellung optisch aktiver, 5, 5′, 6′-trisubstituierter 2,2′-Spirobiindane bekannter Chiralität und enantiomerer Reinheit (1979)
    Springer
    Monatshefte für Chemie 110 (1979), S. 541-565 
    Details
    ISSN: 1434-4475
    Keywords: Configurational correlation ; 5-Ethylindanes ; 1 H-nmr spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Starting from (+) (2R) methyl 5′-ethyl-2,2′-spirobiindane-5-carboxylate of known enantiomeric purity 79 optically active, configurationally correlated 5,5′,6′-trisubstituted 2,2′-spirobiindanes (2–7) were prepared for the purpose of testing a “shortened polynomal Ansatz” for chirality functions. Their optical rotations and1H-nmr spectra are reported. In this context several 6-substituted 5-ethylindanes (1) were prepared as model compounds for synthetic transformations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00938359
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  • 2
    Electronic Resource
    Electronic Resource
    Optisch aktive, aromatische Spirane, 9. Mitt.: Überprüfung eines Näherungsansatzes für Chiralitätsfunktionen bei 5,5′,6′-trisubstituierten 2,2′-Spirobiindanen (1979)
    Springer
    Monatshefte für Chemie 110 (1979), S. 931-946 
    Details
    ISSN: 1434-4475
    Keywords: Ligand parameters ; chirality function ; 2,2′-Spirobiindanes ; 5,5′-disubstituted
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to test the semiempirical value of chirality functions in their mathematically most simple form 23 new optically active 5,5′-disubstituted 2,2′-spirobiindanes1 of known chirality and enantiomeric purity were prepared. Thus a set of about hundred compounds is now available with altogether sixteen types of ligands (i.e. substituents including hydrogen); the experimental molar rotation of fifteen compounds is used to determine the value of a ligandspecific parameter occuring in the used chirality polynomial. According to theory this polynomial is an approximation for the total rotation of derivatives with ligands of three different types and it approximates an experimentally separable part of the rotation as far as compounds with four different ligands are concerned. The additional chirality component, occurring exclusively in the case of derivatives with four different types of ligands turns out to be relatively small but not vanishing. Accordingly, the molar rotation predicted by our method is very good for disubstituted spirobiindanes of type1 and rather good for others with three different types of ligands but is distinctly worse for those with four different ligands. The numerical trend, however, is clearly represented even in cases where our calculation in principle refers to a part of the phenomenon only and the predicted absolute configuration is in call cases in agreement with the experiment. An adequate criterion to judge the quality of our approximation is introduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00906690
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  • 3
    Electronic Resource
    Electronic Resource
    Zur Bildung von Xylol-tricarbonylchrom (Dimethylbenchrotrenen) aus Di-n-butylether und Hexacarbonylchrom (1979)
    Springer
    Monatshefte für Chemie 110 (1979), S. 1067-1075 
    Details
    ISSN: 1434-4475
    Keywords: Di-n-butylether ; 4,4′-dideuterated ; Di-n-pentylether ; Isobutylbenchrotrene ; Methyl-propyl-benchrotrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction of fluorenone ethyleneketal (9), diphenic anhydride as well as of biphenyls such as4 with Cr(CO)6 in refluxing di-n-butylether (BE) gives dimethylbenchrotrenes [xylene-Cr(CO)3,7] which are also formed by refluxing pureBE with Cr(CO)6—although with much lower yields. Similarily, from di-n-pentylether and Cr(CO)6 isobutyl- and 1-methyl-3-propyl-benchrotrene (13 and14) were obtained, whilst from di-n-propyl- and-hexylether, resp., and Cr(CO)6 no benchrotrenes could be isolated. Tentative assumptions on the “catalytic” action of certain functional groups were confirmed by the reaction ofBE and Cr(CO)6 in the presence of carbonamides, such as acetamide, urea and pyrrolidone, where 1,4-dimethylbenchrotrene (7 c) was formed with appreciable yields. Studies using dideuteratedBE showed that—at least for the reaction of9 with Cr(CO)6 (giving a much lower yield of7 than with undeuteratedBE)—a simple bimolecular mechanism can be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00910954
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  • 4
    Electronic Resource
    Electronic Resource
    Stereochemie von Metallocenen, 43. Mitt.: Torsionsisomere Biphenyl-tricarbonylchrom-Komplexe: Darstellung, Konformationsanalyse und Kinetik der Interkonversion (1979)
    Springer
    Monatshefte für Chemie 110 (1979), S. 437-451 
    Details
    ISSN: 1434-4475
    Keywords: Conformational analysis ; Lanthanide induced shift ; NMR, coalescence ; Optical activity ; Rotational barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Complexation of methyl 3-nitro-2-(o-tolyl)-benzoate (2, ano-trisubstituted biphenyl) with hexacarbonyl chromium gave the isomeric Cr(CO)3 complexes3 and4 both existing as two torsional isomersa andb, as seen by nmr. For the main product3 the preferred conformations of the two torsional isomersa andb were deduced by the lanthanide induced shift (LIS) technique. The activation energy for the interconversion process could be determined from kinetic measurements and especially from1H-nmr coalescence temperature of the methylsignals. The barrier of 91±1.5 kJ/mol (21.7±0.3 kcal/mol) in3 reflects the interaction of theo-H-atom of the benzene ring passing the Cr(CO)3 moiety of the benchrotrene ring during the interconversion. A partial optical resolution of3 was achieved by asymmetric reduction with a chiral lithium-aluminium hydride yielding (+)-3 with [α] D 20 +30° (benzene) and the levorotatory alcohol (−)-7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00911932
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