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  • Organic Chemistry  (8)
  • 1995-1999  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis, spectral characteristics and structure of 1,3- and 1,4-disubstituted tetrazolinones (1995)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 636-640 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of ethylene oxide with 1-alkyl- or 1-aryl-1,4-dihydrotetrazole-5-thiones in acetic acid affords the corresponding mesoionic 1-alkyl- or 1-aryl-3-(2-hydroxyethyl)-tetrazolium-5-olates 4-6. The X-ray structure of one of these compounds (5) is presented. On the other hand, the reaction of tetrazolinones with 2-chloroethanol in the presence of potassium hydroxide affords a mixture of the corresponding 1,3- and 1,4-disubstituted isomers. The isomers can be distinguished easily by their IR, 1H or 13C NMR spectra. The fragmentation of these compounds in the mass spectrometer is discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.199533701136
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  • 2
    Electronic Resource
    Electronic Resource
    Kleine Ringe, 86. Versuche zur Darstellung von Alkyltri-tert-butyltetrahedranen auf dem Cyclopentadienon-Weg; photochemisches Verhalten der Cyclopentadienone (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 147-151 
    Details
    ISSN: 0947-3440
    Keywords: Photoisomerization ; Steric hindrance ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small Rings, 86. - Attempts to Synthesize Alkyltri-tert-butyltetrahedranes by the Cyclopentadienone Route; Photochemical Behavior of the CyclopentadienonesOnly the Tetra-tert-butyltetrahedranes 8a-c can be synthesized by photochemical CO extrusion from the corresponding cyclopentadienones 6a-c. This strategy fails with other cyclopentadienones like 6d-f.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950120
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  • 3
    Electronic Resource
    Electronic Resource
    An unexpected product in attempted [4 + 2] cycloadditions of 2,2-diethyl-4,5-dimethyl-2H-imidazoleDedicated to Professor Heinz-Günther Viehe on the occasion of his 65th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1697-1698 
    Details
    ISSN: 0947-3440
    Keywords: 2H-Imidazole ; 1,4-Diazadienes ; [4 + 2] Cycloadditions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,2-Diethyl-4,5-dimethyl-2H-imidazole 1, formally a 1,4-di-azadiene, does not produce [4 + 2] cycloadducts with various electronically-different dienophiles. In the presence of tri-fluoroacetic acid, it tautomerizes to 2,2-diethyl-4-methyl-5-methylene-3-imidazoline 2 and forms a dimer, the structure of which was determined by X-ray crystallography.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199509236
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  • 4
    Electronic Resource
    Electronic Resource
    Structural Aspects of Cyclopropyl Homoconjugation: Experimental Studies and Ab Initio Calculations (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1429-1435 
    Details
    ISSN: 0947-3440
    Keywords: Cyclopropyl homoconjugation ; Molecular structures ; Electron density determinations ; Ab initio calculations ; Spiro compounds ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low-temperature crystal structural studies of a series of saturated and unsaturated bicyclo[2.2.1]heptadiene, heptene and heptane compounds with 7-spirocyclopropyl substitution reveal significant differences in the bond lengths of the three-membered rings and in the C—C single bonds of the bicyclic fragment. A complex interplay of strain and different types of conjugation influence the molecular structure of the bicycloheptadiene derivative 1, where the difference in the length of the three-membered ring bonds is 0.040 Å and all C—C single bonds in the bicyclic fragment are lengthened significantly. Ab initio calculations at the HF/6-31G(d) (to a minor extent) and MP2/6-31G(d) levels are in good agreement with the experimental data. Calculated charge distributions and dipole moments further support the relevance of cyclopropyl homoconjugation in the investigated prototype of Walsh and through-space π-orbital interaction. Static difference electron density maps have been derived from the experimental data by multipole refinements which showed exocyclic shifts of electron density in the planes of the three-membered rings and significant bond ellipticities at the C—C single bonds in the unsaturated bicyclic units.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970721
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  • 5
    Electronic Resource
    Electronic Resource
    Structural Aspects of Cyclopropyl Conjugation: Experimental Studies and Ab Initio Calculations (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2047-2053 
    Details
    ISSN: 0947-3440
    Keywords: Conjugation ; X-ray diffraction ; Molecular structures ; Ab initio calculations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low temperature crystal structural studies of small cyclopropyl-conjugated unsaturated hydrocarbons reveal significant differences in bond lengths between carbon atoms mainly within the three-membered rings but also for adjacent C—C single bonds. The strongest influence of conjugation was observed for spiro[2.4]hepta-4,6-diene (1), where the difference in the lengths of three-membered ring bonds is 0.050 Å (X-ray). The same effect is also obvious from ab initio calculations at HF/6-31G(d) (to a minor extent) and MP2/6-31G(d) levels, as shown by a difference analysis of bond lengths which was performed in order to cancel out systematic errors and differences for both methods. Static difference electron density maps were derived from the experimental data by multipole refinements. These maps showed shifts of electron density to exocyclic locations within the planes of the three-membered rings and significant bond ellipticities for the adjacent single bonds. For 1,1-diethenylcyclopropane (4) a nonsymmetric conformation was found in the crystal lattice, very close to the global minimum structure calculated by ab initio methods.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971007
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  • 6
    Electronic Resource
    Electronic Resource
    Titanium(IV) Chloride Induced Reactions of Ketones and C-Acylimines with Dimethylcyanamide (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1665-1671 
    Details
    ISSN: 0947-3440
    Keywords: C-Acylimines ; Ketones ; Titanium(IV) chloride ; Dimethylcyanamide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of ketones (benzophenone, 4-methylbenzophenone, acetophenone, acetone, and 2,2,4,4-tetramethyl-3-pentanone) and C-acylimines with dimethylcyanamide in the presence of titanium(IV) chloride were investigated, Benzophenone and 4-methylbenzophenone react with dimethylcyanamide to give 4,4-disubstituted 2-dimethylamino-3-aza-1-oxa-1,3-butadienes 5 and 4,4-disubstituted 2-dimethylamino-1-N,N-dimethylcarbamoyl-1,3-diaza-1,3-butadienes 9. Ketones with enolizable hydrogen atoms undergo aldol reactions under these conditions. C-Acylimines 11b-11e, derived from benzil and substituted anilines, undergo [2 + 2] cycloaddition to dimethylcyanamide with subsequent ring opening to 1-(N,N-dimethylcarbamoyl)-2,3,4-triaryl-1,4-diaza-1,3-butadienes 15. 1,2-Diphenyl-2-(isopropylimino)ethanone (11a) reacts with dimethylcyanamide to give 2-dimethylamino-1-isopropyl-4,4-diphenyl-2-imidazolin-5-one (23) in a hitherto unknown multistep reaction. The structure of 23 was confirmed by an X-ray analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961027
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of Sterically Rigid Macrocycles by The Use of Pressure-Induced Repetitive Diels-Alder ReactionsDedicated to Professor Peter Welzel on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 501-516 
    Details
    ISSN: 0947-3440
    Keywords: Repetitive Diels-Alder reactions ; Bis-dienes ; Bis-dienophiles ; endo,exo Stereoselectivity ; High-pressure chemistry ; Cycloadditions ; Macrocycles ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of syn-dimethanotetrahydroanthracene, -tetracene, and -pentacene derivatives 8a-d, 9a-d, and syn-25 are described. Highly stereoselective, pressure-induced Diels-Alder reactions of the bis-dienophiles 8a and/or 9a with the bis-diene 7 lead to the sterically rigid macrocycles 1a, 2a, and 3a/3b, which have well defined cavities of different sizes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970310
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  • 8
    Electronic Resource
    Electronic Resource
    Photoaddition of 2-Morpholinoacrylonitrile to Substituted 1-Acetonaphthones (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1023-1027 
    Details
    ISSN: 0947-3440
    Keywords: Cycloadditions ; Exciplex or diradical intermediate ; 1,4-Ethanonaphthalenes ; Cyclobuta[a]naphthalenes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted 1-acetonaphthones 6b-d and 2-morpholinoacrylonitrile (2a) undergo a photocycloaddition. The type of addition ([2 + 2] vs. [4 + 2]) is dependent on the location of additional substituents. Whereas compound 6c with a methoxy group at C-2 gave only the [4 + 2]-cycloadduct 11, the formation of [2 + 2]-cycloadducts was observed with 6b, d with cyano and methoxy groups, respectively, at C-4. In the case of the 4-bromo derivative 6a, photosubstitution was observed. The endo or exo orientation of the morpholino group in the cycloadducts was determined by an X-ray crystal structure analysis for 9b, as well as by NOE signal intensity difference determination experiments for 9a and 11.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970535
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