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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1221-1225 
    ISSN: 0947-3440
    Keywords: Aggregations ; Circular dichroism ; Cyclophanes ; Molecular recognition ; Supramolecular chemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogen-donor and hydrogen-acceptor substituted chiral cyclophanes with a [2](1,3)benzeno[2](3,5)pyridinophane framework have been synthesized, enantiomerically separated, and analysed by circular dichroism (CD). X-ray structure determination and CD analyses show that these cyclophanes are able to act as hydrogen-bonding donor/acceptor building blocks for the design of chiral supramolecular aggregates with suitable complementary partners. Starting from the pyridinophane N-oxide 4, selective reactions lead to the new chiral pyridinophanes 5-7 in high yields. The X-ray structure analysis of the pyridinophane-2-carbonitrile 5 reveals a multilayered herringbone structure as it forms dimeric aggregates. The CD analysis of the host 7 with the complementary guest molecules melamine and cyanuric acid elucidates the formation of supramolecular complexes in solution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1491-1509 
    ISSN: 1434-193X
    Keywords: Chirality ; Circular dichroism ; Cyclophanes ; Theoretical calculations ; Strained molecules ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chiroptical properties of planar-chiral and helical molecules without stereogenic centres and with well-defined structure, strain, electronic properties and chirality are investigated by experimental and theoretical circular dichroism spectroscopy. We report on the synthetic and theoretical achievements made during the past 10 years in the field of rigid [2.2]metacyclophane propellers, as well as in the area of [n]para- and [n]metacyclophanes containing aliphatic parts like adamantane or unsaturated bridges. Results for carbo and hetero helicenes and helicene-related molecules like twisted phenanthrenes are presented. It is demonstrated how reliable theoretical calculations using configuration interaction and time-dependent methods in combination with density functional theory today are and how useful the interplay between theory and experiment stimulates the development of chiral molecules optimized for this purpose. Even for large molecules it is routinely possible to assign Cotton effects to electronic transitions, to evaluate chromophore contributions, to determine absolute configurations and conformational equilibria, and to discover intramolecular charge transfer effects.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1901-1906 
    ISSN: 0947-3440
    Keywords: Cinnoline pyrolysis ; Circular dichroism ; Cyclophanes ; Dimethylbiphenylene synthesis ; Sulfone pyrolysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 1,8-disubstituted biphenylenes by pyrolysis of azo compounds has been optimized. By means of a continuously working pyrolysis apparatus, the cis isomer 2 can be reliably produced on a gram scale. The chiral syn-[2.2]biphenylenophane 12 has been synthesized by an intermolecular cyclization reaction, subsequent oxidation of the sulfur atoms and pyrolytic extrusion of sulfur dioxide. In an analogous manner, the [2.2]biphenylophane 13 was obtained. The separation of the racemates of the hydrocarbons 12 and 13 could be achieved using a stationary chiral HPLC phase. Compound 12 preferentially adopts a syn conformation in the solid state. The CD spectra of 12 and 13 are compared.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0009-2940
    Keywords: 1-Oxa-[2.2](2,7)naphthalenophane ; Helical molecules ; Ring strain ; Circular dichroism ; Thiaphanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The First Helical Naphthalenophane - Synthesis, Separation off Enantiomers, Circular Dichroism, and Barrier of RacemisationPreparation and properties of the title compound (2; 1-Oxa-[2.2](2,7)naphthalenophane) are described. The enantiomers of 2 were separated or enriched by HPLC on cellulose-tris(3,5-dimethylphenyl)carbamate. Circular dichroism and kinetics of racemisation were elucidated. The energy barrier of ring inversion for the intermediate thia[3.2]phane 9 was determined. Spectroscopic and chiroptical properties are compared to the metacyclophane 1a and the [2.1]naphthalenophane 3.
    Notes: Erstmalige Darstellung und Eigenschaften der chiralen Titelverbindung (2; 1-Oxa[2.2](2,7)naphthalinophan) werden beschrieben. Deren Enantiomere wurden durch HPLC an Cellulose-tris-(3,5-dimethyphenyl)carbamat getrennt bzw. angereichert. Circulardichroismus und Racemisierungskinetik von 2 wurden ermittelt. Außerdem wurde die Energiebarriere für Ringinversion des intermediären Thia[3.2]phans 9 bestimmt. Spektroskopische und chiroptische Eigenschaften von 2 werden anhand des Metacyclophans 1a und des [2.1]Naphthalinophans 3 erörtert.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0009-2940
    Keywords: Circular dichroism ; [2.2]Metacyclophanes ; Helical molecules ; Absolute configuration ; Structure-chiroptic relationships ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intra- und Extraannularly Functionalized Chiral [2.2]Metacyclophanes: Synthesis, Circular Dichroism, and Structure - Chiroptic RelationshipsA simple one-step cyclization reaction for the synthesis of the title compounds 1-5 is presented; separation (enrichment) of enantiomers is achieved by HPLC mainly on (+)-PTrMA. The kinetics of interconversion (racemization) of the new dihetera[2.2]metacyclophanes are determined: No racemization of the internally substituted phanes is found on heating until decomposition, whereas the extraannularly substituted compounds exhibit barriers of interconversion of about 130 kJ/mol, similar to that of the unfunctionalized skeleton 1a. For the pyridinophane 2 the barrier (110 kJ/mol) is lower corresponding to the decreased spatial requirement of the nitrogen lone pair compared to a C-H bond. The circular dichroism curves of the intraannularly functionalized phanes are compared with those of the extraannularly functionalized reference compounds: A bathochromic shift of the Cotton effect at short wavelengths is found, which is increasing with the bulkiness of the internal functional group.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0009-2940
    Keywords: Charge transfer ; Circular dichroism ; Helical molecules ; [2.2]Metacyclophanes ; Structure-chiroptic relationships ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nitro- and Allyloxy-Substituted Helical [2.2]Metacyclophanes: Synthesis, Circular Dichroism and Crystal StructuresThe preparations of the title compound 3a, intraannularly nitro-functionalized, of the extraannularly substituted reference compound 3b, and of the sulfone 4 are described. Enantiomeric resolution of these helical phanes was accomplished on (+)-PTrMA and cellulose tris(3,5-dimethylphenyl)carbamate by HPLC. Racemization of the enantiomers of 3b is faster than that of the previously reported extraannularly substituted phanes. The crystal structure of 3a as well as that of the allyl ether 3d show severe distortions of the benzene rings; the CD spectrum of 3a is pointing at an intramolecular charge-transfer complex, an effect that cannot be evaluated from the CD spectrum of 3b.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0009-2940
    Keywords: Circular dichroism ; Helical molecules ; [2.2]Metacyclophanes ; Oxa[2.2]metacyclophane ; [2.2]Pyridinophanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Helical and Planar-chiral Pyridinophanes - A New Synthesis and Structure/Chiroptic RelationshipsA new two-step synthesis for the strained helical oxa[2.2]phanes 1-5 and for a systematic series of novel structural isomeric (2,4)-pyridinophanes (6-10) is presented. The energy barriers for ring inversion of some intermediate [3.2]phanes and the kinetics of racemization of the [2.2]phanes are determined. Separation and enrichment of enantiomers is achieved by HPLC on cellulose tris(3,5-dimethylphenyl)carbamate and poly(triphenylmethylmethacrylate), resp. The circular dichroism curves of the isomers are compared with those of the corresponding protonated pyridinium compounds. The influence of the chromophor orientation on the circular dichroism is discussed.
    Notes: Eine neue Zweistufensynthese zu den stark ringgespannten, helicalen Oxa[2.2]phanen 1-5 und eine systematische Reihe neuer strukturisomerer (2,4)-Pyridinophane (6-10) werden vorgestellt. Die Energiebarrieren für die Ringinversion der intermediären [3.2]Phane und die Racemisierungskinetik der [2.2]Phane werden gemessen. Racematspaltungen bzw. -anreicherungen gelingen durch HPLC and Cellulose-tris(3,5-dimethylphenyl)carbamat und Poly(triphenylmethyl-methacrylat). Die Circulardichroismen der strukturisomeren Zehnringe und der protonierten Pyridinium-Verbindungen werden gemessen. Die Auswirkung der Chromophor-Orientierung auf den Circulardichroismus wird vergleichend erörtert.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0009-2940
    Keywords: Chirality ; Circular dichroism ; Conformational mobility ; Cyclophanes ; [n]Phanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deformed Chiral [n]MetacyclophanesThe new dithiametacyclophane 3c and the thiaazametacyclophanes 6a, b are chiral, but do not contain chirality centres. They are obtained by cyclization of 1,3-propanedithiol (2), or of the thiaza precursors 5a, b, with the bis(bromomethyl) compounds 1, 4a, b. The dynamic behaviour of the aliphatic chains in 3c, and 6a, b (flipping/rotation) have been studied by dynamic NMR. X-ray analyses of 3c and 6a document the out-of-plane deformation of the boat-shaped benzene ring. The circular dichroism of enantiomer-enriched 3c is reported.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0009-2940
    Keywords: Adamantanophanes ; Calculations, CI ; Circular dichroism ; Cyclophanes ; Strain energy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Exchange of aromatic units (e.g. benzene) for aliphatic/ali-cyclic building blocks (e.g. adamantane) in cyclophanes leads to molecules of the “araliphane” type. The synthesis of the highly strained [2.2](1,3)adamantanometacyclophanes 5a-c is described. The cyclophane skeletons of these molecules are conformationally rigid and therefore 5a-c are planar-chiral. The circular dichroism of 5c has been calculated theoretically with NDDO/MRD-CI methods and was measured. Agreement of theory and experiment is good, a comparison of both allows the assignment of the absolute configuration of the two enantiomers of 5c with high probability. Furthermore, analysis of the nπ* band in the CD spectrum yields a, simple general rule to determine the conformation of the carboxyl group in phenyl ester substructures. Theoretical calculations of the strain energy (Es) of 5c reveal the distribution of strain within the molecule.
    Additional Material: 5 Ill.
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