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  • Inorganic Chemistry  (3,613)
  • AERODYNAMICS  (2,823)
  • 1990-1994  (6,436)
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Year
  • 11
    Electronic Resource
    Electronic Resource
    Photo Diels-Alder Additons, V1 1,4-Photoadditions of α-Morpholinoacrylonitrile to 1-Acylnaphthalenes (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 315-319 
    Details
    ISSN: 0009-2940
    Keywords: Cycloadditions, regio- and stereoselective, light-induced / 1,4-Ethanonaphthalenes / Captodative alkenes / Di-π-methane rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photoexcited 1-naphthaldehyde (1a), 1-acetonaphthone (1b), and 1-naphthophenone (1c) add α-morpholinoacrylonitrile (2a) in a [4 + 2] mode with exceptional regio- and stereoselective formation of only one diastereomer of the two possible regioisomeric 1,4-dihydro-1,4-ethanonaphthalene adducts. An independently formed 1,2-adduct 4 was detected and isolated in very low yield, 4 is thermally and photochemically (313-nm, excitation) cleaved into the starting materials with no indication of direct interconversion into 3b. Compound 3b is stable towards 313-nm radiation, but is efficiently isomerized to give the dihydrobenzosemibullvalene 7 upon 254-nm excitation. - All observations point to the first excited triplet state as the starting point for the 1,4-additions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230216
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  • 12
    Electronic Resource
    Electronic Resource
    Stereochemistry of Dewar Benzenes - Molecular Structures Influenced by Electronic and Steric Effects (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 345-350 
    Details
    ISSN: 0009-2940
    Keywords: Dewar benzene, derivatives, molecular structures of / Substituent effects on molecular structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular structures of the four Dewar benzene derivatives 4-7 were determined by means of X-ray diffraction. The central C1-C4 bonds are extremely long. The carboxylate groups on the bridgehead carbon atoms of 4, 5, and 7 are in optimal orientation for an electronic interaction with the central bonds having high p-character. Therefore the central bonds in 4, 5, und 7 (1.602-1.612 Å) are even more elongated than in 6 (1.563 Å). Repulsion between tert-butyl groups causes bond lengthening and structural deformations. The sp2-hybridized carbon atoms are pyramidalized. From structural comparison of Dewar benzene derivatives a strong correlation between the length of the central bond and the folding angle of the four-membered rings can be derived. A new rule has been established for the thermal stability of Dewar benzene derivatives.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230220
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  • 13
    Electronic Resource
    Electronic Resource
    Neue wasserlösliche makrobicyclische Großhohlräume (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 375-379 
    Details
    ISSN: 0009-2940
    Keywords: Cyclophanes / Hostguest chemistry / Macrocyclic compounds / Phanes / Supramolecular chemistry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Watersoluble Macrobicyclic CavitiesThe watersoluble macrobicyclic compounds 1, 3, 5a, and 5b have been synthesized for the first time bearing large endolipophilic cavities of different sizes and shapes. They were studied with respect to their interactions towards lipophilic guest compounds. The “in/out” isomerism of the hitherto largest endolipophilic cavities 4a, 4b, 5a, and 5b has been investigated by 1H-, 13C-NMR spectroscopy and FAB mass spectrometry. The absence of significant 1H-NMR high-field shifts in hostguest studies is attributed to the rigidity of cavities 1 and 3, whilst the isomeric cavities 5a and 5b contain very large openings. Orientational fluorescence spectroscopy investigations, however, suggest hostguest interactions of the isomers 5a and 5b with ammonium 8-anilino-1-naphthalenesulfonate (8,1-ANS).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230224
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  • 14
    Electronic Resource
    Electronic Resource
    Elektrophile β-Bromierung und nucleophile α-Methoxylierung α,β-ungesättigter Carbonylverbindungen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 399-404 
    Details
    ISSN: 0009-2940
    Keywords: β-Halovinyl ketones / β-Halovinyl aldehydes / α-Alkoxyvinyl ketones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrophilic β-Bromination and Nucleophilic α-Methoxylation of α,β-Unsaturated Carbonyl CompoundsOximes 29a, b, semicarbazones 11a-d, dimethylhydrazones 4, and [3-methyl-2(3H)-benzothiazolylidene]hydrazones 23a-c of unsaturated aldehydes and ketones are brominated at the β-carbon by an addition-elimination sequence (→ 21a,b, 13a-d, 7, and 27c, respectively). When unsaturated ketone hydrazones are treated with bromine and methanol the α-methoxy-β-bromo derivatives 35a-c are obtained, which after hydrolysis and hydrobromic acid elimination give α-methoxy substitution products 36a-c of the starting compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230227
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  • 15
    Electronic Resource
    Electronic Resource
    Electron-Density Distribution in the Bonds of a Dewar Benzene Derivative (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 341-343 
    Details
    ISSN: 0009-2940
    Keywords: Difference electron densities / Dewar benzene, derivative ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We determined the difference electron densities [X-X] in the bonds of a Dewar benzene derivative from low temperature X-ray data (94 K). The density maxima on all bonds are significant. The central bond with an internuclear distance of 1.594 Å has a strong bending character. From the difference densities a bending angle of 28° can be derived.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230219
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  • 16
    Electronic Resource
    Electronic Resource
    Zur Stereoselektivität der intramolekularen Diels-Alder-Reaktion von 1,7,9-Decatrien-3-onen zu Octalonderivaten (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 363-374 
    Details
    ISSN: 0009-2940
    Keywords: Diels-Alder reaction, intramolecular / 1,7,9-Decatrien-3-ones / Octalone derivatives / Siloxycyclopropanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselectivity of Intramolecular Diels-Alder Reactions of 1,7,Q-Decatrien-3-ones to Octalone Derivatives2-Alkenyl-substituted 2-siloxycyclopropanes 1 and 2 serve as protected enone equivalents and are converted into key building blocks 5-8 in excellent yields. After desilylation and ring cleavage these compounds provide 1,7,9-decatrien-3-ones 9-12, which undergo smooth intramolecular Diels-Alder reaction at room temperature or approximately 100°C. The resulting octalone derivatives 13-16 are formed with exclusive or preferred cis connection of the rings. The relative configurations of the cycloadducts are secured by equilibration experiments and NMR spectroscopy (selective proton decouplings). For 11 → 15 and 12 → 16 the cis selectivitiy can remarkably be enhanced by trifluoroacetic acid catalysis. This high noninduced diastereoselectivity is caused by the endo approach of the reactive molecular sites, whereas the configuration of the third stereogenic centre (C-2) is determined by the folding of the linking carbon chain. Preference of a boat conformation with equatorial ester group endo-Beq may be assumed and appears to be general for intramolecular cycloadditions of such trienones. This effect as well as the influence of further substituents at the diene or dienophile portion on stereoselectivity and the reactions of other model compounds are discussed.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230223
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  • 17
    Electronic Resource
    Electronic Resource
    Novel Access to Polyazamacrocycles: Non-Template Cyclization of Terephthalaldehyde and Aliphatic Polyamines (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 405-406 
    Details
    ISSN: 0009-2940
    Keywords: Polyazamacrocycles / Cyclization, non-template / Terephthalaldehyde / Polyamines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Non-template [2+2] condensation of terephthalaldehyde with bis(3-aminopropyl)amine and N,N'-bis(3-aminopropyl)-1,2-diaminoethane leads to macrocyclic systems that can be reduced and derivatized further, whereas a similar reaction with bis(2-aminoethyl)amine leads to polymeric material only.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230228
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  • 18
    Electronic Resource
    Electronic Resource
    Deuterierte Bicyclo[3.2.0]heptan-2-one und ihre NMR-Spektren (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 411-412 
    Details
    ISSN: 0009-2940
    Keywords: Bicyclo[3.2.0]heptan-2-one, deuterated ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deuterated Bicyclo[3.2.0]heptan-2-ones and their NMR Spectra[3,3-2H2]-, [6,7-2H2]-, [6,6-2H2]-, and [7,7-2H2]bicyclo[3.2.0]heptan-2-ones were prepared, starting from 2-cyclopenten-1-one (1). Using these derivatives, the 13C- and 1H-NMR spectra of bicyclo[3.2.0]heptan-2-one (2) have been assigned.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230230
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  • 19
    Electronic Resource
    Electronic Resource
    Die Borierung von Lactamen und Harnstoffen mit einem Amino-imino-boran (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 455-458 
    Details
    ISSN: 0009-2940
    Keywords: N-Boryl lactams / Isourea, triborated / Isothiourea, triborated /N/O Borotropism / Calculations, MNDO ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Contribution to the Chemistry of Boron, 201. - Boration of Lactams and Ureas by an Amino-Imino-BoranePyrrolidon reacts with (tert-butylimino)(2,2,6,6-tetramethylpiperidino)borane (1) to give the N-borated lactam 2. Diketopiperazine behaves similarly. It is borated on both of its N atoms to form 3. Urea and 1 give access to the O,N,N′-triborated isourea derivative 4, which contains the structural unit of a ketiminoborane. The diborated carbodiimide 10 is ultimately obtained from 1 and thiourea via the triborated isothiourea derivative 9. MNDO calculations have been used to estimate the relative thermodynamic stabilities of O/N borotropes of carbonic acid amides and lactams. They demonstrate that the O isomers gain in stability by increasing the size of N substituents.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230307
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  • 20
    Electronic Resource
    Electronic Resource
    Lithium-Verbindungen eines Chlorsilanols und von Fluor-funktionellen Siloxanolen; Reaktionen und Kristallstrukturen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 449-453 
    Details
    ISSN: 0009-2940
    Keywords: Lithium salts / Chlorosilanol / Fluorosilanolates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithium Compounds of a Chlorosilanol and of Fluoro-Functional Siloxanols; Synthesis and Crystal StructuresThe lithiated disilanol (CMe3)2Si(OH)2 (1) serves as a starting material in the reaction with halosilanes for the stepwise construction of siloxanols (4, 5, 7). 4 and 7 react with n-C4H9Li to give the lithium compounds 6 and 8, respectively. 6 crystallizes in hexane as a trimer with planar three-coordinated lithium, bonded to two Si-O atoms and one Si - F atom. 8 reacts in THF with LiF elimination to give cyclotrisiloxane 9. The chlorosilanol 2 is prepared by hydroxy-chlorine exchange in 1 with PCl5. The stable lithium derivative of 2 (3) forms a dimeric THF adduct with tetrahedral lithium.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230306
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