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  • Electronic Resource  (5)
  • Loose Leaf
  • 2010-2014
  • 1980-1984  (5)
  • 1960-1964
  • 1890-1899
  • 1870-1879
  • 1980  (5)
  • Heterocycles
  • Synthetic methods
  • 1
    Electronic Resource
    Electronic Resource
    Thermal and Photochemical Transformations of Hetero-1,3,5-hexatrienes into Five-Membered Rings - Possible Pericyclic ReactionsDocument No. NDRL-1955 from the Notre Dame Radition Laboratory. (1980)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 19 (1980), S. 973-983 
    Details
    ISSN: 0570-0833
    Keywords: Hetero-1,3,5-hexatrienes ; Pericyclic reactions ; Photochemistry ; Cyclization ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterosubstituted 1,3,5-hexatrienes undergo thermal and photochemical cyclizations, most of which can be viewed as pericyclic reactions. Numerous cyclizations of this type have been reported in the literature. This article presents a systematic account of such reactions, classified according to the number and nature of the heteroatoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198009731
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    1,5,-Electrocyclizations - An Important Principle of Heterocyclic ChemistryRobert Burns Woodward - In Memoriam (1980)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 19 (1980), S. 947-973 
    Details
    ISSN: 0570-0833
    Keywords: Electrocyclic reactions ; Cyclization ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The principle of orbital control of pericyclic reactions has deepened our understanding of reaction phenomena and provided an excellent classification of these one-step processes. The electrocyclic reaction of the pentadienyl anion ⇌ cyclopentenyl anion type is relatively unimportant in all-carbon systems and has not even been verified in the case of the parent compound. In the heterocyclic series, however, where up to five C-atoms of the pentadienyl anion are replaced by heteroatoms, a multitude of ring closures and ring openings find their ordering principle in the mentioned electrocyclic reaction. The replacement of the carbon atoms by heteroatoms can take place isoinically, i. e., with retention of the anionic character, or isoelectronically. An isoelectronic replacement of CR2 in position 1 by NR2 OR, and or CR in position 3 by NR or O leads to a charge-free resonance structure for the open-chain species; the migration of the charge during the electrocyclization results in a correlation with a cyclic zwitterion. Conversely, isoelectronic exchange of CR in position 2 by NR or O produces a conjugated 1,3-dipole, which cyclizes to a charge-free unsaturated five-membered ring. Twofold isoelectronic exchange allows the whole process to take place in a cation. Selected examples are to shed light on the classification and the thermodynamics of this electrocyclic reaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198009473
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  • 3
    Electronic Resource
    Electronic Resource
    The Synthesis of Unusual Organic Molecules from Azoalkanes. New analytical methods (33)Dedicated to Professor Alfred Roeding on the occasion of his 70th birthday (1980)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 19 (1980), S. 762-779 
    Details
    ISSN: 0570-0833
    Keywords: Azoalkanes ; Synthetic methods ; Strained molecules ; Cage compounds ; Polycycles ; Photochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal or photochemical denitrogenation of azoalkanes constitutes an effective and convenient method for the preparation of unusual organic molecules, including highly ringstrained, sterically crowded, fluxional, antiaromatic and other interesting structures. The importance of this synthetic approach is that the azo linkage serves as a means of introducing the critical (usually last) bond in the complex target molecule. This article presents a cross-section of such elegant synthetic utilization of azoalkanes for fused-, bridged- and spiro-cyclization. Our coverage of the large body of literature has been directed by the complexity and novelty of the products. Azoalkanes are usually prepared via cycloaddition of azo dienophiles to appropriate substrates.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198007621
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  • 4
    Electronic Resource
    Electronic Resource
    Electrophilic Reagents - Recent Developments and Their Preparative ApplicationDedicated to Professor Matthias Seefelder on the occasion of his 60th birthday (1980)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 19 (1980), S. 151-171 
    Details
    ISSN: 0570-0833
    Keywords: Electrophilicity ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The most widely known electrophilic agents are protic acids and compounds with an electronsextet partial structure. Recent research has aimed at the development of new electrophilic reagents, with greater reactivity on the one hand and higher selectivity on the other, which would largely obviate the addition of Lewis acids (Friedel-Crafts catalysts), and also allow control of the isomer ratio in reactions with ambivalent substrates. Compounds with “super-leaving groups”, such as trifluoromethanesulfonate and fluorosulfate, have been demonstrated as most advantageous in this respect since they are sufficiently polarized or dissociated for reactions to take place even in the absence of Friedel-Crafts catalysts. Heterocycles such as pyridones or imidazole are likewise suitable leaving groups; they are employed for their high selectivity, and also because they allow working under non-aqueous conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198001513
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  • 5
    Electronic Resource
    Electronic Resource
    Heterocyclic Analogues of Methylenecyclopropanes (1980)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 19 (1980), S. 276-289 
    Details
    ISSN: 0570-0833
    Keywords: Methylenecyclopropanes ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterocyclic three-membered rings with an exocyclic double bond merit special interest in view of their ring strain and their fascinating chemistry. Their synthesis, thermal decomposition, ring opening, and cycloaddition reactions will be discussed in this review. α-Lactams, alkylideneaziridines, diaziridinones, and diaziridinimines belong to the best known classes, but the chemistry of alkylideneoxiranes and -thiiranes, α-lactones, α-thiolactones, thiiranimines, and aziridinimines has also been studied to some extent. Two elusive three-membered rings are oxiranimines and thiaziridinimines; the former were postulated as reactive intermediates in the thermal decomposition of α-lactams, whereas the latter were trapped efficiently with double and triple bonds during thermolysis of N-sulfonyliminothiatriazolines. In spite of many attempts to prepare thione derivatives of the title compounds, they are still unknown. Included in this review are also some open-chain dipolar species which are isomeric with the heterocyclic three-membered rings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.198002761
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    Paper (German National Licenses)
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