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  • 1
    Electronic Resource
    Electronic Resource
    Pyrazole-Organoboranes, VII. Addition Complexes of Pyrazolylboranes (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1285-1291 
    Details
    ISSN: 0009-2940
    Keywords: Aminoboranes ; Boron-nitrogen heterocycles ; N-Base-Organoboron adducts ; Steric interactions ; Fluctuation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The monomeric 9-pyrazolyl-9-borabicyclo[3.3.1]nonanes react in situ with either excess of 9H-9-BBN or of some pyrazoles to form the 2:1 or 1:2 adducts 1-5 or 7-11, respectively. Spectroscopic data (NMR, IR) suggest and the solid state structure of 4 confirms the presence of a central heterocycle in complexes of the type 1-5. In solutions of 7-11 NMR data at room temperature indicate a rapid exchange of the four nitrogen atoms of the two pyrazole rings at the boron atom of the 9-BBN moiety. In the solid state (X-ray structure of 8) intermolecular N-H⃛N bonds lead to dimeric structures. In the almost insoluble adduct 7 a polymeric structure is suggested. Pyrazoles with large substituents, e. g. 3,5-diphenylpyrazole (P2Pz) give addition complexes of the type 1-5 only in solution in equilibrium with the corresponding monomeric species (11B NMR) and none of the type 7-11.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230611
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  • 2
    Electronic Resource
    Electronic Resource
    Pyrazole - Organoboranes, VIII Thermal C - Borylation in Crowded Pyrazolylboranes (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1699-1704 
    Details
    ISSN: 0009-2940
    Keywords: Boron-nitrogen heterocycles ; Pyrazoles ; Aminoboranes ; Steric interactions ; Trialkylboranes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Crowded 3,5-disubstituted pyrazoles, e. g. 3,5-di-tert-butyl-,3,5-di-tert-butyl-4-methyl-, or 3,5-di-tert-butyl-4-ethylpyrazole [(tb)2Pz, (tb)2mPz, or (tb)2ePz, respectively], fail to react with activated trialkylboranes (e. g. BEt3* or BPr3*) at 110°C, even after prolonged heating. At 170°C the reaction of (tb)2Pz with activated triethylborane gives the monomeric diethyl(3,5-di-tert-butyl-1-pyrazolyl)borane (3). At 220-230°C the dimeric boracycles (4)2 are mainly formed [X-ray structure of (4a)2]. In contrast, the reactions of these crowded pyrazoles with tetraalkyldiboranes(6) commence just above room temperature. Diethylhydroborane adducts (5) of 3 and dimeric alkyl(3,5-di-tert-butyl-1-pyrazolyl)-boranes (2b)2 and (2c)2 are the main products.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240805
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation and Some Reactions of (Acylamino)diorganoboranes (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 565-570 
    Details
    ISSN: 0009-2940
    Keywords: Amides ; Boranes, trialkyl- ; Boranes, dialkylhydro- ; Boron-nitrogen heterocycles ; Bis(9H-9-borabicyclo[3.3.1]nonane) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The carboxamides RCONH2 [R=Ph (1), tBu (2)] react with BEt3 and with (9H-9-BBN)2 to give the (acylamino)diethylboranes 3, 4 and the 9-acylamino-9-BBN 5, 6, respectively. Compounds 3 and 4 are largely monomeric (NMR) in solution and dimeric as crystalline solids [X-ray structure of (4)2]. The 9-BBN derivatives 5 and 6 are associated and probably polymeric in solution (NMR). The 1:1 adducts 7 and 8 containing the ring (X-ray structure of 7) are formed on the reaction of 3 and 4 with (9H-9-BBN)2 by borane exchange. The former is also obtained directly by treating compound 1 or 2 with (9H-9-BBN)2. Compound 7 reacts at 140-150°C to give the air-stable heterocycle 11 (X-ray structure).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260303
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