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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3813-3830 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Migration of Alkyl Group in Sextett RearrangementsThe migration aptitude of alkyl groups in the Beckmann-, the Criegee-, and the isonitrile-nitrile rearrangements were investigated. The relative rearrangement rates of substituted benzyl groups are an expression of the charge on the migrating carbon at transition state. From the relative rates of migration of exo- and endo- 2- norbornyl group the geometrical changes at the migrating carbon are estimated. Finally, The different influence of α-branching in the migrating group is discussed for these and some other rearrangements.
    Notes: Die Wanderungstendenzen von Alkylgruppen bei der Beckmann- Criegee- und Isonitril-Nitril-Umlagerung werden untersucht. Aus den relativen Reaktionsgeschwindigkeiten der substituierten Benzylreste werden Rückschlüsse auf die Ladungsverteilung im Übergangszustand dieser Reaktionen gezogen und aus dem Verhältnis der Wanderungstendenzen des exo und endo- 2- Norbornylrestes auf die Geometrie der wandernden Gruppe im Übergangszustand. Der in verschiedenen Sextettumlagerungen unterschiedliche Einfluß der α-Methylverzweigung in der wandernden Gruppe wird interpretiert.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 1509-1524 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Isomerisation of Homoadamantane-3-carboxylic Acid into Homoadamantane-1-carboxylic AcidIt is shown by D-, 13C-, and double labelling experiments that the title isomerisation 2 → 3 unter Koch-Haaf conditions is due to reversible decarbonylation followed by intermolecular hydride transfer between the bridgehead positions of the two bridgehead homoadamantane cations and homoadamantane derivatives. The isomerisation is accompanied by complete equilibration of an isotopically labelled methylene group over all possible positions. This is due to the known adamantylmethyl-3-homoadamantyl cation rearrangement which is likewise occuring. In contrast to hydride transfer reactions in the adamantyl system the methylene groups of the homoadamantyl system are not participating in the hydride transfer between the bridgehead positions.
    Notes: Durch D-, 13C- und Doppelmarkierungsexperimente wird gezeigt, daß die Isomerisierung der Homoadamantan-3-carbonsäure (2) zur Homoadamantan-1-carbonsäure (3) unter den Bedingungen der Koch-Haaf-Synthese durch reversible Decarbonylierung zustande kommt, die von intermolekularem Hydridtransfer zwischen den Brückenkopfpositionen der Homoadamantan-1-und Homoadamantan-3-carbenium-Ionen und Homoadamantanderivaten begleitet ist. Die Umlagerung ist mit Äquilibrierung der Isotopenmarkierung aller Methylengruppen verbunden. Hierfür wird die gleichzeitig stattfindende bekannte Adamantylmethyl-3-Homoadamantylcarbenium-Umlagerung verantwortlich gemacht. Im Gegensatz zu Hydridübertragungen im Adamantyl-system beteiligen sich die Methylenwasserstoffe des Homoadamantylsystems nicht an der Hydridübertragung zwischen den Brückenköpfen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 360-366 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Evidence for 4-Homocubyl Carbenium Ions as Reactive Intermediates4-(Hexafluoroisopropoxy)homocubane (6) is the main product of the thermolysis reaction of N-(4-homocubyl)-N-nitrosoacetamide (9) and of the solvolysis reaction of 4-homocubyl bromide (5) in hexafluoro-2-propanol. This is experimental evidence for 4-homocubyl carbenium ions as intermediates in both reactions. The solvolysis rate of 4-homocubyl bromide at 120°C in the same solvent (k1120°C=1.3 · 10-7s-1) by far exceeds that of 1-norbornyl bromide which does not react at a detectable rate under these conditions. According to force field calculations the strain enthalpy is increasing by as much as 66 kcal · mol-1 in the ionisation of 4-homocubyl bromide. Therefore nonclassical stabilization of the 4-homocubyl carbenium ion is postulated.
    Notes: Bei der Thermolyse von N-(4-Homocubyl)-N-nitrosoacetamid (9) und bei der Solvolyse von 4-Homocubylbromid (5) in Hexafluor-2-propanol entsteht 4-(Hexafluorisopropoxy)homocuban (6) als Hauptprodukt. Dies beweist das Auftrete von 4-Homocubyl-Carbenium-Ionen als Zwischenstufen beider Reaktionen. Die Solvolysegeschwindigkeit von 4-Homocubylbromid bei 120°C in Hexafluor-2-propanol (k1120°C = 1.3 · 10-7 s-1) ist wesentlich höher als die von 1-Norbornylbromid, dessen Solvolyse unter diesen Bedingungen nicht nachweisbar ist. Da die Ionisation von 4-Homocubylbromid nach Kraftfeldrechnungen mit 66 kcal · mol-1 Ansteigen an Spannungsenthalpie verbunden ist, wird für das 4-Homocubyl-Carbenium-Ion eine nichtklassische Stabilisierung angenommen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1259-1261 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Simple Synthesis of 5-Cyano-2-pyridinecarboxylic Acid and its AmideThe title compounds 3 and 2 (X = CN) are prepared in good yields by regioselective carbamoylation of 3-cyanopyridine in a Minisci reaction and by consecutive amide hydrolysis with amyl nitrite in HCl-saturated acetic acid. The observed regioselectivity apparently remains confined to carbamoyl and possibly acyl radicals and to - M-effect substituents in 3-position.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 4674-4681 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Fluorescent Dyes with Large Stokes Shifts - a Simple Synthesis of [2,2′-Bipyridine]-3,3′-diol[2,2′-Bipyridine]-3,3′-diol (4) is obtained in one step from furoin (8) by Zincke rearrangement in 32% yield. The fluorescence quantum yield of the dye is 50% in chloroform - absorption and fluorescence spectra are completely separated (TZ = 1011). The large Stokes shift is caused by a proton transfer according to the Förster mechanism.
    Notes: [2,2′-Bipyridin]-3,3′-diol (4) wird aus Furoin (8) in einem Schritt über die Zincke-Umlagerung in 32proz. Ausbeute erhalten. Die Fluoreszenzquantenausbeute des Farbstoffs beträgt in Chloroform 50% - Absorptions- und Fluoreszenzspektrum sind vollständig getrennt (TZ = 1011). Für den großen Stokes-Shift ist ein intramolekularer Protonentransfer nach dem Förster- Mechanismus verantwortlich.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1075-1078 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Fluorescent Dyes with Large Stokes Shifts - Soluble DihydropyrrolopyrroledionesThe synthesis of 3,6-Diaryl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-diones 1a-d and 3,6-Diaryl-2,5-dihydro-2,5-dimethylpyrrolo-[3,4-c]pyrrole-1,4-diones e-h is described. By substitution of the aryl groups with tert-butyl groups, photostable fluorescent dyes with high solubility in organic solvents are obtained. If a conformational conversion follows the excitation, Stokes shifts up to 70 nm with fluorescent quantum yields up to 95% are obtained.
    Notes: Die Synthese von 3,6-Diaryl-2,5-dihydropyrrolo[3,4-c]pyrrol-1,4-dionen 1a-d und 3,6-Diaryl-2,5-dihydro-2,5-dimethylpyrrolo[3,4-c]pyrrol-1,4-dionen e-h wird beschrieben. Durch Einführen von tert-Butylgruppen in die Arylreste werden leichtlösliche Fluoreszenzfarbstoffe erhalten. Über den Mechanismus einer konformativen Umwandlung nach der Anregung werden Stokes-Shifts bis zu 70 nm bei Fluoreszenzquantenausbeuten von bis zu 95% erzielt.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1881-1884 
    ISSN: 0009-2940
    Keywords: 1,7-Diazaperylene ; Dyes, fluorescent ; Fluorescence, slid-state ; Meerwein arylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of 1.7-DiazaperyleneThe hitherto unknown 1,7-Diazaperylene (2) has been prepared in a five-step synthesis from 1,5-diaminoanthraquinone (3) by a Meerwein arylation reaction. Applications as a fluorescent dye are discussed.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 529-535 
    ISSN: 0009-2940
    Keywords: Perylene dyes ; Hydrocarbons polycyclic ; Fluorescent dyes ; Fluorescent labelling ; Fluorescent tracer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Nonsymmetrically Substituted Perylene Fluorescent DyesA general method for the preparation of perylene-3,4:9,10-tetracarboxdiimides 1 with two different substituents at the nitrogen atoms is described: The easily prepared symmetrical tetracarboxdiimides 1 (R1=R2) are transformed into carboxdiimide anhydrides 2 and condensed with primary amines to the corresponding tetracarboxdiimides 1 (R1 ≢ R2). Applications as fluorescent tracers in biochemistry and polymer chemistry are discussed.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 3381-3383 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Unusual Melt Behaviour of Mixtures of 1- and 3-Homoadamantanecarboxylic AcidsMixtures of 1- and 3-homoadamantanecarboxylic acids give an unusual phase diagram which reveals the formation of a 1 : 1 addition compound. This diagram allows one to explain the fact that sharp melting points, which differed only slightly from each other in absolute value, were reported in the literature for samples derived from synthetic procedures, which, in fact, give mixtures of these two acids.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2907-2913 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A Quantitative Description of Polarity of Binary solvent Mixtures Using Different Polarity ScalesThe solvent polarities of 12 binary mixtures have been examined using 6 polarity scales as a function of their composition. They are quantitatively described by a simple, closed form, two-parameter equation which can explain e.g. deviations from linear correlations of polarity scales for mixtures.
    Notes: Die Lösungsmittelpolaritäten von 12 binären Gemischen sind als Funktion ihrer Zusammensetzung unter Berücksichtigung von 6 Polaritätsskalen untersucht worden. Sie erfüllen alle quantitativ eine Zwei-Parameter-Gleichung, mit deren Hilfe u.a. Abweichungen von der linearen Korrelation der Polaritätsskalen bei Gemischen erklärt werden können.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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