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  • 1
    Electronic Resource
    Electronic Resource
    Beiträge zur Chemie des Bors, 219. (Di-tert-butylphosphanylimino)(2,2,6,6-tetramethylpiperidino)boran: ein BNP-1,3-“Dipol” (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1995-2002 
    Details
    ISSN: 0009-2940
    Keywords: Boranes, amino(phosphanylimino)- ; Phosphaborolines ; Iminophosphoranes ; 1,3,2,5-Oxazaphosphaboroles ; 1,3,4,2-Thiazaphosphaboroles ; 1,3,4,2-Diazaphosphaboroles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Contributions to the Chemistry of Boron, 219[1]. - (Di-tert-butylphosphanylimino)(2,2,6,6,-tetrametylpiperidino)borane: a BNP 1,3-„Dipole”In contrast to amino-imino-boranes R2N-BN-R', which are susceptible to [2 + 2] cycloadditions, the amino(phosphanyl-imino)borane 2 [R = P(tBu)2] performs [3 + 2] cycloadditions with heteroallenes X≡C≡Y or nitriles to yield the novel five-membered heterocycles 3a-g, 6, 7, and 8. The reactions of 2 are dominated by the phosphorus atom as the nucleophile attacking the carbon atom in X≡C≡Y and R-CN, respectively. The driving force for the formation of the new heterocycles is obviously provided by the formation of an iminophosphorane structure and a three-coordinated environment at the boron atom. The X-ray-structures of 3a, 3c, 3e, and 3g demonstrate planer heterocyclic rings.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260905
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  • 2
    Electronic Resource
    Electronic Resource
    Direct Synthesis of Organometallics, IVPart III: Ref.[1].. The Mechanism of the Activation of Aromatic Hydrocarbons with Lithium Atoms: Spectroscopic Results and Their Ab initio Interpretation (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1369-1371 
    Details
    ISSN: 0009-2940
    Keywords: C—H bond activation ; Lithium atoms ; Mechanism ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of THF, lithium atoms are known to be able to activate benzene derivatives under cryogenic reaction conditions. This synthesis affords solid lithium hydride and ring-metalated products selectively. For the determination of the reaction mechanism, the cocondensation reaction was repeated on a reduced scale in a 77-K cryostate, which allowed the measurement of UV/Vis and IR spectra. The spectroscopic results exclude any generation of free electrons; their interpretation suggests that small solvated lithium clusters activate the hydrocarbon bonds. A model reaction was developed by using the spectroscopic results and ab initio calculations. Thus, benzene was added to a Li2 cluster, which reduces the carbon-hydrogen bond to the phenyl anion and hydride on the surface without the formation of free radicals. In the last step the intermediate mixed organolithium species dismutate to solid lithium hydride and phenyllithium.The reduction process on the cluster surface is facilitated by coordinating THF to the lithium, which results in a higher redox potential. The complete mechanism is discussed in the terms of geometries of the intermediates and reaction enthalpies in connection with the experimental values. Thus, a distinct new reaction pathway for a substitution on the benzene ring is established.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961291109
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