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  • 1
    ISSN: 0947-3440
    Keywords: Benzyl 2,3-dioxobutyrate ; 2-Iso-oxacephems ; Antibacterial activity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: General methods have been developed for the synthesis of 7-amino-2-iso-oxacephem-4-carboxylic acid esters 21a,b; 35b. Clayfen [Fe(III) nitrate supported by montmorillonite] was used for the preparation of benzyl 2,3-dioxobutyrate (3). The latter readily reacted with N(1)-unsubstituted β-lactams (9a, 28) to give products formed by addition reaction on the middle carbonyl-C atom. These intermediates furnished the corresponding acetoacetic esters 10, 29 which gave by ring closure the O-mono- and the O,N-diprotected-2-iso-oxacephems (11, 30). Intermolecular carbene insertion was used for the synthesis of tert-butyl 2-(2-oxoazetidin-1-yl)acetoacetates 19a,b whose ring closure led to the tert-butyl 2-iso-oxa-cephem-4-carboxylates 20a,b. The O-protecting tert-butyl group could be removed without decomposition of the 2-isooxacephem moiety to give 2-iso-oxacephem-4-carboxylic acids 2a,b which exhibit antibacterial activity against Grampositive microorganisms.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 104 (1971), S. 290-300 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reductive Rearrangements of the Retrobenzilic Acid Type Induced by Lewis Acids, VI. Crossing ExperimentsBy a series of crossing experiments the reductive retrobenzilic acid rearrangements of 5,5-diaryldithiohydantoins (1) and 4,4-diaryl-2-imidazoline-5-thiones (3), induced by aluminium chloride and yielding the corresponding 4,5-diaryl-4-imidazoline-2-thiones (2) and 4,5-diarylimidazoles (4), respectively, were shown to proceed intramolecularly.
    Notes: Durch eine Serie von Kreuzungsversuchen wird der intramolekulare Verlauf der durch Aluminiumchlorid ausgelösten reduktiven Retrobenzilsäure-Umlagerung von 5.5-Diaryl-dithiohydantoinen (1) und 4.4-Diaryl-Δ2-imidazolin-thionen-(5) (3) zu 4.5-Diaryl-Δ4-imidazolin-thionen-(2) (2) bzw. 4.5-Diaryl-imidazolen (4) erwiesen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermally Induced Reactions of Imidazole Derivatives, III. Thermal Rearrangement Akin to the Retrobeazlic Rearrangement of 2,4,4-Triaryl-5-alkylthio-, -5-aralkylthio-, and -5-arylthio-4H-imidazolesThermolysis of the title compounds (1) furnishes, under elimination of the sulfur containing group, the corresponding 2,4,5-triarylimidazoles (2). The sulfur containing group can be recovered as the corresponding dialkyl-and bis(aralkyl)disulfides, respectively, and/or as thioketones and transformation products of the latter. A free radical mechanism is suggested.
    Notes: Die Thermolyse der Titelsubstanzen (1) führt unter Abspaltung der schwefelhaltigen Gruppe zu den entsprechenden 2,4,5-Triarylimidazolen (2). Die schwefelhaltige Gruppe findet sich in Form des entsprechenden Dialkyl- bzw. Bis(aralkyl)disulfids und/oder Thioketons bzw. deren Folgeprodukten wieder. Für die Umwandlungen wird ein radikalischer Mechanismus nahegelegt.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 1649-1653 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermally Induced Reactions of Imidazole Derivatives, IV. Thermal Rearrangements of 2,4,4-Triaryl-5-methylthio-4H-imidazoles. A Crossing ExperimentThe 1,2 aryl shift in the course of the thermal rearrangement of 2,4,4-triaryl-5-methylthio-4H-imidazoles into 2,4,5-triarylimidazoles has been demonstrated to proceed intramolecularly with the aid of a crossing experiment.
    Notes: Mit Hilfe eines Kreuzversuchs wird gezeigt, daß die 1,2-Arylverschiebung bei der thermisch induzierten Umlagerung von 2,4,4-Triaryl-5-methylthio-4H-imidazolen (1) in 2,4,5-Triaryl-imidazole (2) intramolekular verläuft.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Hydantoins, Thiohydantoins and Glycocyamidines, XXXI Reductive Rearrangements of the Retrobenzilic Acid Type Induced by Lewis Acids, VII The Anomalous Behaviour of 5.5-Dibenzyldithiohydantoin and of 4-4.Dibenzyl-2.5-bis-(methylthio)-4H-imidazoleOn refluxing 5.5-dibenzyldithiohydantoin (1d) and 4.4-dibenzyl-2.5-bis(methylthio)-4H-imidazole (2d) with aromatic hydrocarbons in the presence of aluminium chloride one of the C-benzyl groups is cleaved off the heterocycle and transferred to the solvent.
    Notes: Beim Kochen des 5.5-Dibenzyl-dithiohydantoins (1d) und des 2.5-Bis-methylmercapto-4.4-dibenzyl-4H-imidazols (2d) mit aromatischen Kohlenwasserstoffen in Gegenwart von Aluminiumchlorid wird eine der C-Benzylgruppen vom Heteroring abgespalten und auf das Lösungsmittel übertragen.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 1645-1648 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermally Induced Reactions of Imidazole Derivatives, IV. Kinetics of the Thermal Rearrangement of 2,4,4-Triaryl-5-methylthio-4H-imidazolesThe thermal rearrangements of the title compounds 1a - d into the 2,4,5-triarylimidazoles 2 in different solvents and at different temperatures are first order reactions. No linear relation exists between the effect of the p-substituents of the migrating aryl groups on the reaction rates and their Hammett-Brown σ+ values. The solvent has practically no effect on the rearrangement rate of 1c. The activation parameters of the rearrangement 1c → 2c are given.
    Notes: Die thermische Umlagerung der Titelsubstanzen 1a - d in die 2,4,5-Triarylimidazole 2 in verschiedenen Lösungsmitteln und bei verschiedenen Temperaturen folgt einem Geschwindigkeitsgesetz 1. Ordnung. Der Einfluß des p-Substituenten der wandernden Arylgruppe ändert sich nicht linear mit den Hammett-Brownschen σ+-Werten. Das Lösungsmittel hat praktisch keinen Einfluß auf die Umlagerungsgeschwindigkeit von 1c. Die Aktivierungsparameter der Umlagerung 1c → 2c werden angegeben.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermally Induced Reactions of Imidazole Derivatives, VII: Thermal Rearrangements of 2,4,4-Triaryl-5-methylthio-4H-imidazoles in the Absence of Hydrogen Sources. A Novel Type of HexaarylbiimidazolylThermolysis of 2,4,4-tris(4-chlorophenyl)-5-methylthio-4H-imidazole (1b) and of 2,4,5-tris(4-chlorophenyl)-1-[2,4,5-tris(4-chlorophenyl)-2H-imidazol-2-yl]imidazole (4b) furnishes the same novel hexakis(4-chlorophenyl)-1,1′-biimidazolyl (8b). The formation of 8b is considered as an additional proof of the free radical mechanism of the thermolysis of the title compounds.  -  On the basis of their 13C NMR spectra the triarylimidazolyl dimers of type C are shown to possess structure 6 rather than structure 7 as hitherto assumed.
    Notes: Thermolyse von 2,4,4-Tris(4-chlorphenyl)-5-methylthio-4H-imidazol (1b) und 2,4,5-Tris(4-chlorphenyl)-1-[2,4,5-tris(4-chlorphenyl)-2H-imidazol-2-yl]imidazol (4b) liefert das gleiche neue Hexakis(4-chlorphenyl)-1,1′-biimidazolyl (8b). Die Bildung von 8b wird als zusätzlicher Beweis für den radikalischen Mechanismus der Thermolyse der Titelverbindungen angesehen.  -  Aufgrund der 13C-NMR-Spektren wird gezeigt, daß die den Triarylimidazolyl-Dimeren (Typ C) zugeschriebene Struktur 7 unrichtig und durch die Struktur 6 zu ersetzen ist.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 3610-3620 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Anisotropy Effects of Conjugated Cyclic Systems, IV. 1H NMR Spectra of Mesityl-Substituted 2,6-Dimethylbenzene DerivativesThe effect of very different substituents X on the chemical shift differences Δδ of the o- and p-methyl group 1H NMR signals of 4′-X-substituted 2,2′,4,6,6′-pentamethylbiphenyl derivatives is ±0.045 ppm only. In comparison with X = H (0.47 ppm) electron attracting substituents like X = N2⊕ increase Δδ values up to 0.53, X = CN and NO2 up to 0.52 ppm; electron releasing groups X = OH, NH2 reduce Δδ down to 0.45 and OCH3 to 0.44 ppm. Even in the 2-mesityl-substituted 1,3,5-trimethyltropylium ion (2) Δδ rises only up to 0.54 ppm.
    Notes: Die Differenz der chemischen Verschiebungen Δδ zwischen den 1H-NMR-Signalen der o- und p-Methylgruppen in den Mesitylresten 4′-X-substituierter 2,2′,4,6,6′-Pentamethylbiphenyl-Derivate 1 wird mit ±0.045 ppm relativ wenig durch sehr verschiedene Substituenten verändert. Gegenüber X = H (0.47 ppm) erhöhen stark elektronenziehende Substituenten X = N2⊕ auf 0.53 und X = CN, NO2 auf 0.52; elektronenspendende Gruppen wie X = OH, NH2 verkleinern Δδ auf 0.45 und OCH3 bis 0.44 ppm. Selbst im 2-mesitylsubstituierten 1,3,5-Trimethyltropylium-Ion (2) beträgt Δδ nur 0.54 ppm.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 815-821 
    ISSN: 0170-2041
    Keywords: Aztreonam analogues ; Carumonam analogues ; β-Lactams ; Antibiotics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analogues of aztreonam (1a) and carumonam (1b) were prepared by acylation of 3-aminomonobactamic acid derivatives with several new and known isoxazoleacetic and isoxazolecarboxylic acid derivatives 3-10. None of the resulting new monobactams 11-18, 41a, 41b, and 54a exhibited any significant antibacterial activity.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1434-193X
    Keywords: Single-electron transfer ; Ring contractions ; 1,4-Dihydro-1,2,4-triazine ; Photochemical reduction ; Chemical reduction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Chemical reduction (Zn/AcOH) of the arene 1 and of 2(4),5-dihydro-1,2,4-triazine 7 has been reinvestigated, resulting in the amendment of literature data concerning this reaction. Chemical, electrochemical, and photochemically induced reductions and ring contractions of 1,2,4-triazine derivatives have been compared. The first example of a triaryl-1,4-dihydrotriazine has been prepared. Some further evidence is presented that supports the proposed mechanism of the photochemically induced reduction and ring contraction of 1,2,4-triazines.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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