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  • 1
    Electronic Resource
    Electronic Resource
    Cyclophanes, XXVII. [2.2]Indenophane Mono- and Dianions: Preparation and Nuclear Magnetic Resonance Spectra (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 737-744 
    Details
    ISSN: 0009-2940
    Keywords: Cyclophane anions ; Indene derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclophane, XXVII. - [2.2]Indenophan-Mono-und Dianionen: Darstellung und kernmagnetische Resonanz-SpektrenDie Darstellung, chemischen und physikalischen Eigenschaften negativ geladener polycyclischer Cyclophane werden beschrieben. Through-space-elektronische Wechselwirkungen und through-space-Anisotropieeffekte werden aus den Protonen- und Kohlenstoffkernresonanzspektren abgeleitet. Die untersuchten Systeme gehören zu zwei Hauptgruppen: a) paratrope 4nπ-polycyclische Dianionen, z. B. [2.2]Benzo[g]chrysenocyclophan-Dianion (122-) und b) (4n + 2)π-polycyclische Mono- und Dianionen, die diatrop sind. In den Dianionen sind beide Decks geladen: z. B. syn-[2.2]Indenocyclophan-Dianion (132-) und sein anti-Isomer (142-). Bei den untersuchten Monoanionen handelt es sich um die des [2.2]-Benzoindenocyclophans (151-), 4,5,17,18-Tetramethyl[2.2]benzoindenocyclophans (161-) und des 12-Methyl[2.2]benzoindenocyclophans (171-). Die spektroskopischen Eigenschaften der lagigen Anionen werden mit denjenigen von 1,4-Dimethylindenyl-Anion (111-) und mit Literaturwerten der neutralen Cyclophane 1-11 verglichen. Es wird eine Trennung von Anisotropie- und chargetransfer-Effekten durchgeführt, die es erlaubt, die Netto-through-space-Wechselwirkung abzuschätzen.
    Notes: The preparation and chemical and physical properties of negatively charged polycyclic cyclophanes are reported. The throughspace electronic interactions and the through-space anisotropy effects were deduced from proton and carbon nuclear magnetic resonance data. The systems studied belong to two main groups: a) 4nπ-polycyclic dianions which are paratropic, e.g. [2.2]benzo-[g]chrysenophane dianion (122-), and b) (4n + 2)π-polycyclic mono- and dianions, which are diatropic. In the dianions both layers are charged, e. g. syn-[2.2]indenocyclophane (132-) and its anti isomer (142-). The monoanions studied are [2.2]benzoindenocyclophane (151-), 4,5,17,18-tetramethyl[2.2]benzoindenocyclophane (161-), and 12-methyl[2.2]benzoindenocyclophane (171-). The spectroscopic properties of the layered anions were compared with those of 1,4-dimethylindenyl anion (111-) and with literature data of neutral cyclophanes, viz. 1-11. A differentiation between the anisotropy and charge-transfer effects has been made and it enables the estimation of the net through-space interaction.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220422
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  • 2
    Electronic Resource
    Electronic Resource
    Cyclophanes, XXXVIII. [2]Metacyclo[2]indenophanes: Synthesis, Anions and Iron ComplexesDedicated to Professor Klaus Hafner on the occasion of his 65th birthday. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 167-175 
    Details
    ISSN: 0009-2940
    Keywords: Cyclophanes ; Indenyl anions ; Iron complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [2.2]Metacyclophane can be directly formylated according to the Rieche method to give 4-formyl[2.2]metacyclophane (12) in 44% yield. The synthesis of the [2]metacyclo[2]indenophane 8 from the aldehyde 12 by the pathway previously employed for the corresponding [2.2]paracyclophanes failed due to the harsh conditions of the cyclization step. An alternative synthesis of 8 and its isomer 9 involving the construction of the five-membered ring prior to that of the cyclophane unit succeeded. Compounds 8 and 9 were obtained as an 82:18 mixture, deprotonation of which afforded the anion 10, which shows long-term stability. The 1H-NMR spectrum of this anion does not exhibit a through-space charge transfer due to its structure. The 1H-NMR parameters and molecular mechanics calculations are discussed. Both faces of 10 react in the presence of FeCl2 · 2 THF and a twentyfold excess of LiCp to give a 70:30 mixture of the ferrocene derivatives 7 and 35.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260125
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  • 3
    Electronic Resource
    Electronic Resource
    Hydroxide Ion Initiated Reactions Under Phase Transfer Catalysis Conditions: Mechanism and Implications. New Synthetic Methods (62) (1986)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 25 (1986), S. 960-970 
    Details
    ISSN: 0570-0833
    Keywords: Phase-transfer catalysis ; Catalysis ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The development of Phase Transfer Catalysis (PTC) represents a major step forward in the employment of many organic reactions and renders them very convenient and useful processes. These reactions involve the application of nucleophiles in general, anions and bases in particular, in reactions carried out in a water-organic solvent system. They can be performed both in the laboratory and on an industrial scale. The ease of application of PTC processes is the main reason for their increasing utilization in industry. An outstanding achievement of this technique is the employment of aqueous bases in reactions which traditionally would otherwise require a strong base in a nonaqueous medium. The classical procedures that require severe anhydrous conditions, expensive solvents and dangerous bases such as metal hydrides and organometallic reagents are now replaced by aqueous solutions of, e.g., sodium or potassium hydroxides (PTC/OH processes). In contrast to the extensive synthetic applications of PTC/OH systems, the detailed mechanisms of these processes have been the subject of a great deal of controversy and various mechanisms have been suggested. However, it would seem that our knowledge concerning the mechanistic aspects of such reactions has now reached the stage where it can be used to advantage in synthesis planning. A better understanding of the various factors which influence the reaction would undoubtedly help to optimize PTC/OH processes such as to enable higher yields in shorter reaction times at lower temperatures. The importance of, inter alia, the catalyst will be pointed out and it is highly recommended that such catalysts be always available in the laboratory, for the range of organic reactions that they can efficiently, conveniently and safely catalyze is vast indeed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198609601
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