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  • Organic Chemistry  (7)
  • Wiley-Blackwell  (7)
  • American Chemical Society
  • Molecular Diversity Preservation International
  • 2000-2004
  • 1985-1989  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Über 1,2-Umlagerungen und C—H-Einschubreaktionen Acyclischer AlkylidencarbeneHerrn Prof. Dr. Dr. H. G. O. Becker zum 65. Geburtstag gewidmet (1987)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 49-54 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On 1.2-Shift Reactions and C—H-Insertions of Acyclic Alkylidene CarbenesTwo series of acyclic terminal vinyl bromides (1…4 and 5…7) were tested in the reaction with potassium tert-butoxide as precursors of alkylidene carbenes. As expected 1 up to 4 only give 1-alkynes whereas the 2-methylated vinyl bromides 5, 6 and 7 yield 1-methylated cyclopentenes predominantly besides 2-alkynes. The formation of cyclopentenes indicates a reaction route via alkylidene carbenes and 1,5-C—H-insertion reactions, that of 2-alkynes is convincing evidence for 1,2-alkyl shift reactions in 2-methyl substituted alkylidene carbenes. The selectivity of 1,5-C—H-insertion depends on the degree of alkyl substitution of the C-5-atom. At 240°C the selectivity is 1°:2°:3° ≈ 1:54:240.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19873290107
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  • 2
    Electronic Resource
    Electronic Resource
    Photochemical Dediazoniation of Arene Diazonium Salts sensitized by zinc phthalocyanine tetra(sulfomorpholide)Herrn Prof. Dr. R. Mayer zum 60. Geburtstag gewidmet (1986)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 328 (1986), S. 729-740 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photo-excited zinc phthalocyanine tetra(sulfomorpholide) (ZnPcTSM) sensitizes the dediazoniation of arene diazonium salts via electron transfer. 1ZnPcTSM* reacts with p-methyl-, p-methoxy-, and p-diethylamino benzenediazonium tetrafluoroborate, respectively, diffusion-controlled, 3ZnPcTSM* with rate constants 3.3 × 107, 8.5 × 107, and 1.1 × 108 M-1 s-1.Quantum yields of the dye bleaching by p-methoxy benzenediazonium tetrafluoroborate show that the singlet reaction proceeds due to symmetry-allowed back electron transfer with very low efficiency, whereas the triplet reaction reaches the ISC quantum yield at [ArN2⊕] ≍ 10-3 M.In the triplet reaction an exciplex is formed as proved by the temperature dependence of the quenching rate constants and direct spectroscopic determination (τexciplex = 157 μs). From ΔG≠ of the quenching reaction the solvation reorganization parameter λ0 and the reaction distance (r = 0.37 nm) are calculated.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19863280511
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of the Dipole Moment of the Charge-Shift Triplet Exciplex from zinc phthalocyanine tetrasulfomorpholide and p-methoxy-benzenediazonium tetrafluoroborateDedicated to Prof. Dr. M. Schulz on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 989-994 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Triplet exciplexes are known to have usually relatively low polarities, in contrast to singlet exciplexes. It is shown that triplet quenching rate constants of the title system can be used to determine the exciplex dipole moment if it is (plausibly) assumed that the dissociation rate constants of charge-shift exciplexes only depend on the viscosity but not on the polarity of the solvent.The quenching rate constants kq of the title system in various acetonitrile/acetone or acetonitrile/ethylacetate mixtures are determined and treated by an adapted McRAE equation developed for UV-VIS absorption spectroscopic data.The dipole moment of p-methoxy-benzenediazonium tetrafluoroborate necessary for the solution of the McRAE equation is estimated by a Hammett correlation of known data which gives by extrapolation μ(p-MeO—C6H4N2⊕BF4⊖) = 31.4 × 10-30 Cm (9.4 Debye). Using this value and a cavity radius of 3.7 × 10-10m (cp. [1]) μex3(ZnPcTSM…p-MeO-C6H4N2⊕BF4⊖)* = 16.0 × 10-30 cm (4.8 Debye) is obtained. According to this value the triplet exciplex studied has a lower polarity than the starting diazonium salt.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310613
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  • 4
    Electronic Resource
    Electronic Resource
    Synthese von rac-Cinera-5,7,11-trien-9-on (1985)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1985 (1985), S. 560-565 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of rac-Cinera-5,7,11-trien-9-oneThe spiro trienone 22 isolated from a Cineraria species has been synthesized as racemate by intramolecular alkylation starting with 5-isopropyl-3-methylphenol via a suitable phenol substituted in position 2. This compound gave no Diels-Alder reaction with itself. Accordingly, the naturally occurring dimer 23 cannot be an artifact. The corresponding spiro dienones 15 and 16 have also been prepared.
    Notes: Das Spirotrienon 22, das aus einer Cineraria-Art isoliert wurde, wird ausgehend von 5-Isopropyl-3-methylphenol (2) über ein geeignetes 2-substituiertes Phenol durch innermolekulare Alkylierung in Form seines Racemats synthetisiert. Diese Verbindung geht keine Diels-Alder-Reaktion mit sich selbst ein. Daher kann das natürlich vorkommende Dimere 23 kein Kunstprodukt sein. Die entsprechenden Spirodienone 15 und 16 werden ebenfalls dargestellt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198519850317
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  • 5
    Electronic Resource
    Electronic Resource
    1,2,3-Triazine, III Synthese von N-Aminopyrazolen und deren Oxidation zu 1,2,3-Triazinen. Molekülstruktur des 1,2,3-Triazins (1985)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1985 (1985), S. 1732-1751 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2,3-Triazines, III. - Synthesis of N-Aminopyrazoles and their Oxidation to 1,2,3-Triazines. Molecular Structure of 1,2,3-TriazineOxidation of the N-aminopyrazoles 4a - i affords the 1,2,3-triazines 5a - i. Spectra and reactions - such as oxidation, reduction, and cycloaddition reactions - of some 1,2,3-triazines 5 are described. The X-ray analysis of 5a is presented.
    Notes: Die Oxidation der N-Aminopyrazole 4a - i liefert die 1,2,3-Triazine 5a - i. Es werden Spektren und Reaktionen - wie Oxidation, Reduktion und Cycloadditionen - einiger 1,2,3-Triazine 5 beschrieben. Die Röntgenstrukturanalyse für 5a wird angegeben.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198519850903
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  • 6
    Electronic Resource
    Electronic Resource
    Structure of Two Oxidation Products of β-Lumicolchicine: A Remarkable Reaction with Active Manganese Dioxide (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 1075-1079 
    Details
    ISSN: 0170-2041
    Keywords: β-Lumicolchicine, oxidation with active manganese dioxide, oxidation with m-chloroperbenzoic acid ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Struktur zweier Oxidationsprodukte des β-Lumicolchicins: Eine ungewöhnliche Reaktion mit aktivem MangandioxidZwei ungewöhnliche Reaktionsweisen von MnO2 und m-Chlor-perbenzoesäure mit der tetrasubstituierten C=C-Bindung von β-Lumicolchicin (1-β) werden beschrieben. Aktiver Braunstein oxidiert die 7a,10b-Cyclobutendoppelbindung, wobei in 10b-Position eine Hydroxygruppe eingeführt und am C-Atom 7a unter Einbeziehung der Acetamido-Seitenkette ein 2-Oxazolinring geschlossen wird (2). Mit m-Chlorperbenzoesäure ergibt 1-β kein Epoxid, sondern unter Öffnung des Vierrings ein 1:1-Addukt (3). Die Kristallstrukturanalyse von 2 läßt intermolekulare Wechsel-wirkungen zwischen den OH-Gruppen und den Stickstoffatomen erkennen. 13C-NMR-Spektroskopie mit Doppelquantenkohärenz (INADEQUATE-Pulsfolge) zeigt, daß 2 in Lösung die gleiche Struktur wie im Kristall besitzt und beweist die Struktur von 3. Außer den 13C-NMR-Signalen von 2 und 3 werden auch die der stereoisomeren Lumicolchicine 1-β und 1-γ zugeordnet. Ferner werden die 13C, 13C-Kopplungskonstanten für 2 und 3 ermittelt.
    Notes: Two unusual reaction types of MnO2 and of m-chloroperbenzoic acid with the tetrasubstituted C=C bond of β-lumicolchicine (1-β) are presented. Active MnO2 oxidizes the 7a,10b cyclobutene double bond by adding a hydroxy group to the position 10b while the acetamido side chain is used to close a 2-oxazoline ring in position 7a (2). m-Chloroperoxybenzoic acid splits the cyclobutene ring of 1-β and forms a ketonic 1:1 adduct (3) instead of an epoxide. X-ray structure analysis of 2 reveals intermolecular interaction between the hydroxy groups and the nitrogen atoms. 2D-INADEQUATE 13C-NMR spectroscopy establishes structure 2 in solution, proves the structure of 3, and allows also to assign the 13C-NMR signals of the tetracyclic skeleton of the stereoisomeric lumicolchicines 1-β and 1-γ. Furthermore, 13C,13C coupling constants were determined for 2 and 3.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890271
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  • 7
    Electronic Resource
    Electronic Resource
    Enhydrazine, 38. Unterscheidung von 1,5,6,7-Tetrahydro-4H- und 2,5,6,7-Tetra-hydro-4H-indazol-4-onen im 13C-NMR-Spektrum (1985)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1985 (1985), S. 794-801 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Enhydrazines, 38. Discrimination between 1,5,6,7-Tetrahydro-4H- and 2,5,6,7-Tetrahydro-4H-indazol-4-ones in the 13C NMR SpectrumFrom the title compounds the isomeric pairs 1a, b, 4a, b, and 5a, b were prepared. The spectroscopic properties of the regioisomers were investigated. Only the 13C NMR signals of the C atoms 3 and 7 a are significantly different within a pair and can be used for a reliable assignment. The structure of 1b was assigned by an X-ray analysis.
    Notes: Von den Titelverbindungen wurden die Isomerenpaare 1a, b, 4a, b und 5a, b dargestellt. Von den spektroskopischen Eigenschaften der Regioisomeren sind nur die 13C-NMR-Signale der C-Atome 3 und 7 a innerhalb eines Paares signifikant verschieden und für eine sichere Zuordnung geeignet. 1b wurde durch eine Röntgenstrukturanalyse gesichert.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198519850415
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