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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 4632-4636 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of 2-Methyl-4H-1,3-benzoxazin-4-ones and Related Compounds4H-1,3-benzoxazin-4-ones 2 are smoothly prepared via (acylimino)phosphoranes 1 by intramolecular condensation analogous to a Wittig reaction. Tert. phosphanes are used for the preparation of the (acylimino)phosphoranes 1 which are converted into the corresponding benzoxazines and tert. phosphane oxides, e.g. 2-methyl-4H-1,3-benzoxazin-4-one (2a) which, in spite of some attempts, has not been obtained before.
    Additional Material: 4 Tab.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1914-1922 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure of Spiro[1,3,2λ5-benzoxaza (diaza)phosphole-2,5′λ5-dibenzophospholes]o-Aminophenols or o-phenylenediamines react with 5,5-dibromodibenzophospholes to give spirophosphoranes 1-6. The 31P-, 13C- and 1H-NMR spectra are independent of temperature, therefore, no evidence of a permutation process was detectable. As an example the structure of the heterocyclic compound 4,6-di-tert-butyl-1-ethyl-1,3-dihydro-2-phenylspiro[2H-1,3,2λ5-benzodiazaphosphole-2,5′-λ5-dibenzophosphole] (5) was determined by X-ray crystallography. The compound crystallizes in the space group P212121 with Z=4. The five-membered rings are attached to the phosphorus in an equatorial-axial manner. The phenyl and the NH group occupy equatorial positions, the N-C2H5 substituent is axially located. According to the geometry determined an assignment of the NMR coupling constants was done. Spiro compounds 1-6 show a very similar geometry.
    Notes: o-Aminophenole oder o-Phenylendiamine reagieren mit 5,5-Dibromdibenzophospholen zu Spirophosphoranen 1-6. Die 31P-, 13C- und 1H-NMR-Spektren sind temperaturunabhängig, so daß keine Hinweise für eine Permutationsisomerisierung aufgefunden wurden. Die Struktur wurde am Beispiel des 4,6-Di-tert-butyl-1-ethyl-1,3-dihydro-2-phenylspiro[2H-1,3,2λ]5-benzodiazaphosphol-2,5′-λ5-dibenzophosphols (5) bestimmt. Die Verbindung kristallisiert in der Raumgruppe P212121 mit Z=4. Die Fünfringe sind äquatorial-axial an den Phosphor gebunden. Der Phenylrest und die NH-Gruppe besetzen äquatoriale Positionen, der N-C2H5-Substituent ist axial gebunden. Damit können die NMR-Kopplungen zugeordnet werden. Die Spiroverbindungen 1-6 besitzen eine vergleichbare Geometrie.
    Additional Material: 1 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1679-1685 
    ISSN: 0009-2940
    Keywords: EPR ; ENDOR ; Phenoxy radicals ; Chiral recognition ; Noe's reagent ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the racemic phenols I and II with chiral auxiliaries like the acid chloride III and particularly the lactols IV and V (Noe's reagent) leads to diastereomeric esters and acetals, respectively. The products may be synthesized either in the EPR sample tube or under preparative conditions with subsequent separation of the diastereomers by chromatographic methods. Oxidation of the phenols with lead dioxide in inert solvents provides the corresponding phenoxyls, which are investigated by EPR and ENDOR spectroscopy. The most striking features of these spectra are the differences in the β-proton coupling constants of up to several Gauss, indicating a significant alteration of the hyperconjugation angle. These results are interpreted in terms of the population of specific conformations favored by stereoelectronic and steric interactions, which are confirmed by careful investigations of the shielding and deshielding effects in the 1H-NMR spectra of the corresponding phenols.
    Additional Material: 4 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 103 (1970), S. 1279-1285 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of Paramagnetic Tin Heterocycles2-Amino-4,6-di-tert-butylphenoxyl (1) reacts with aryltin halides to give 8-membered heterocycles (3-7) which exhibit paramagnetism. The course of the reaction and the properties of these stable radicals, particularly of the Sn-HFS, are described.
    Notes: 2-Amino-4.6-di-tert.-butyl-phenoxyl (1) reagiert mit Arylzinnhalogeniden unter Bildung 8-gliedriger paramagnetischer Heterocyclen (3-7). Der Reaktionsweg und die Eigenschaften, insbesondere die Sn-Hyperfeinstruktur der stabilen Radikale, werden untersucht.
    Additional Material: 2 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 109 (1976), S. 2231-2242 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Chemical Properties of 2,3-Dihydro-1,3,2λ5-benzoxazastibolesThe synthesis of the benzoxazastiboles 1-9 starting from o-aminophenols and triarylantimony dibromides (route A) or o-aminoaroxyls and triarylstibines (route B) is described. These heterocycles do not react with bases, however with mineral acids solvolysis is observed. Temperatures above 25°C lead to further reactions, and finally a new nine-membered ring can be isolated. Under oxidative conditions a cleavage of the oxazastiboles takes place, and phenoxazinyl radicals are formed from the fragments. The regiospecifity of this reaction was confirmed by means of e.s.r. spectroscopy.
    Notes: Die Synthese der Benzoxazastibole 1-9 aus o-Aminophenolen und Triarylantimondibromiden (Weg A) oder o-Aminoaroxylen und Triarylstibinen (Weg B) wird beschrieben. Gegenüber basischen Reagentien sind die Heterocyclen stabil, während im sauren Medium Solvolyse erfolgt. Bei Temperaturen oberhalb 25°C findet Weiterreaktion zu neungliedrigen Ringsystemen statt. Unter oxidativen Bedingungen werden die Oxazastibole gespalten, wobei Phenoxazinyl-Radikale entstehen. Die Regiospezifität dieser Reaktion wird durch ESR-Untersuchungen nachgewiesen.
    Additional Material: 2 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 282-287 
    ISSN: 0899-0042
    Keywords: phenoxyl radicals ; hydrogen bond ; host guest interactions ; diastereomers ; absolute configuration ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral recognition with magnetic methods requires the formation of diastereomers. Due to the variety of appropriate reactions, hydrogen bond formation, esterification, and acetalization as well as host-guest interactions were chosen for basic investigations. The results obtained indicate that in the case of diamagnetic compounds the chemical shifts and for paramagnetic compounds the β-proton coupling constants are the most useful parameters. By combination of both pieces of information, assignment of the absolute configuration was achieved. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 316 (1983), S. 678-684 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Synthese von vier verschiedenen dreizähnigen Azomethin-Liganden wird beschrieben. 1H- und 13C-NMR-Untersuchungen zeigen, daß diese Verbindungen in einem Tautomeriegleichgewicht mit den entsprechenden Benzoxazolinen vorliegen. Die Liganden reagieren mit Zn2+, Cd2+ und Pb2+ sowohl in homogener Phase als auch in wäßrigen Lösungen zu diamagnetischen Chelaten, die durch Luftsauerstoff oder Bleidioxid zu paramagnetischen Komplexen oxidiert werden können. Die gut aufgelösten ESR-Spektren zeigen Hyperfeinstrukturen und g-Faktoren, die für die Metallionen charakteristisch sind. Die Nachweisgrenze für Zinkionen liegt je nach Arbeitsweise bei 0,6 ppm bis 6,5 ppb, für Cadmiumionen bei 0,56 ppm. Ein qualitativer Nachweis für Zn2+ in verschiedenen Schmierölen wurde durchgeführt.
    Notes: Summary The synthesis of four different three-dentate azomethine ligands is described. By 1H- and 13C-NMR investigations an equilibrium with the corresponding benzoxazolines was detected. The ligands form diamagnetic chelates with Zn2+, Cd2+ and Pb2+, as well in homogeneous as in aqueous solutions. These chelates can be converted to paramagnetic complexes by oxidation with air oxygene or lead dioxide. The well resolved ESR spectra exhibit hyperfine structures and g-values according to the metal ions chelated. The detection limit for zinc ions was determined, depending on the reaction conditions, to 0.6 ppm–6.5 ppb, and for cadmium ions to 0.56 ppm. An application of the ligands for the qualitative detection of zinc in lubricants is described.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 286 (1977), S. 59-64 
    ISSN: 1618-2650
    Keywords: Analyse von Zinnorganoverbindungen ; Elektronenspin-Resonanz ; Reaktion mit o-Aminophenolen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Di- und Triorgano-Zinn-Verbindungen reagieren glatt mit substituierten o-Aminophenolen in Gegenwart von Luftsauerstoff zu stabilen paramagnetischen Komplexen. Die beobachteten ESR-Spektren zeigen große Zinnaufspaltungen. Diese Kopplungskonstanten variieren stark mit den organischen Resten der eingesetzten Zinnverbindungen, so daß sie ohne weiteres analytisch ausgewertet werden können. Die Reaktion läßt sich entweder in homogener Lösung oder als Extraktion einer wäßrigen Phase durchführen. Die Komplexe können auch in Konzentrationen 〈10−7 leicht nachgewiesen werden. Darüberhinaus findet die Umsetzung auch bei Einwirkung der Aminophenollösung auf Organozinnstabilisatoren, die z. B. in PVC enthalten sind, statt, so daß diese direkt qualitativ in Polymeren bestimmt werden können. Die Radikalstabilität, die Linienbreiten, das Assoziations- und das Sättigungsverhalten wurden für die Umsetzung von Diphenylzinndichlorid mit 2-Amino-4,6-di-tert.-butyl-phenol sorgfältig untersucht, so daß unter den angegebenen Bedingungen eine quantitative Bestimmung aromatischer Organozinnverbindungen leicht durchgeführt werden kann.
    Notes: Abstract Di- and Triorganotin derivatives react very smoothly with substituted o-aminophenols in the presence of air oxygen to form stable paramagnetic complexes. The ESR spectra observed exhibit a large tin coupling. These splitting constants depend strongly on the organic part of the tin compounds used. Therefore, a direct analytical determination is possible. The reaction takes place either in homogenous solution or as an extraction of an aqueous phase. The complexes are easily detected even at concentrations 〈10−7 molar. Furthermore, the paramagnetic tin complexes are formed with organotin stabilizers for example in PVC; therefore, a direct qualitative analysis of these compounds in polymers can be performed. The radical stability, the line width and the association and saturation properties are carefully investigated for the reaction of diphenyltindichloride with 2-amino-4,6-di-tert.-butyl-phenol. These results indicate a convenient possibility of a quantitative analysis of aromatic tin compounds under the conditions given.
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  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 82 (1970), S. 481-482 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 90 (1978), S. 392-393 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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