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  • 1
    ISSN: 0947-6539
    Keywords: asymmetric catalysis ; aziridines ; chiral ligands ; palladium compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chiral palladium π-allyl intermediate for the catalytic asymmetric synthesis shown in Scheme 1 has been isolated as the PF-6 salt. MM 2 calculations have been performed and the structure of the palladium complex in solution has also been investigated by means of NMR spectroscopy. Both the computational and spectroscopic results suggest that in the complex the bidentate bis(aziridine) ligand adopts a conformation that forces the π-allyl moiety out of the normally preferred square-planar geometry. This nicely explains the very high enantioselectivity observed in the title reaction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 106 (1994), S. 625-646 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Herstellung enantiomerenreiner Verbindungen nimmt innerhalb der Organischen Chemie einen weiten Raum ein. Besonderes Augenmerk liegt dabei auf der Nutzung natürlich vorkommender Ausgangsmaterialien und auf der Entwicklung von Methoden zur enantioselektiven Umsetzung achiraler Substrate. Chirale Aziridine sind in diesem Zusammenhang eine attraktive Verbindungsklasse, da sie über eine Vielzahl von Verfahren enantiomerenrein oder in hohen Enantiomerenüberschüssen verfügbar sind und zudem auf verschiedenste Weise in der asymmetrischen Synthese genutzt werden können. Die Chemie der Aziridine wird durch ringöffnende Reaktionen bestimmt, deren Triebkraft in der Aufhebung von Ringspannung liegt. Durch geeignete Wahl der Substituenten an Stickstoff- und Kohlenstoffatomen gelingt es, in ringöffnenden Reaktionen mit unterschiedlichsten Nucleophilen einschließlich metallorganischen Verbindungen exzellente Stereo- und Regiokontrolle zu erzielen. Dadurch werden chirale Aziridine zu wertvollen Substraten für die Synthese wichtiger biologisch aktiver Vebindungen, z.B. Alkaloiden, Aminosäuren und β-Lactam-Antibiotika, Diastereoselektive Synthesen unter Substratkontrolle sind möglich, wenn Aziridine als abspaltbare chirale Auxiliare eingesetzt werden. Nach Metallierung am Ringkohlenstoffatom können Aziridine auch als chirale Reagentien in der asymmetrischen Synthese benutzt werden. Da chirale Bisaziridine auch als Liganden für Übergangsmetalle wirken können, rükken Anwendungen in dem herausfordernden Gebiet der enantioselektiven Katalyse ins Blickfeld.Der Ausschluß dreigliedriger Carbo-und Heterocyclen aus dem Werkzeugkasten des organischen Chemikers erscheint heutzutage unvorstellbar[1].
    Additional Material: 6 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 101 (1989), S. 665-670 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 28 (1989), S. 649-654 
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 9 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 33 (1994), S. 599-619 
    ISSN: 0570-0833
    Keywords: Nitrogen heterocycles ; Asymmetric synthesis ; Aziridines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of enantiomerically pure compounds is one of the major areas of organic chemistry. Much emphasis is placed on the elaboration of naturally occurring starting materials and on the development of techniques for enantio-selective transformations of achiral substrates. In this field, chiral aziridines form an attractive class of compounds, since they are available in enantiomerically pure (or highly enriched) form by a variety of procedures and can be used for asymmetric synthesis in a number of different ways. The chemistry of aziridines is dominated by ring-opening reactions, the driving force for which is relief of ring strain. By suitable choice of sub-stituents on the carbon and nitrogen atoms, excellent stereo- and regiocontrol can be attained in ring-opening reactions with a wide variety of nucleophiles, including organometallic reagents; this makes chiral aziridines useful as substrates for the synthesis of important biologically active species including alkaloids, amino acids, and /Mactam antibiotics. Substrate-controlled diastereo-selective synthesis is also possible by use of aziridines as removable chiral auxiliaries, while metalation at a ring carbon atom allows aziridines to be used as chiral reagents for asymmetric synthesis. Chiral bisaziridines can act as ligands for transition metals, and applications in the challenging field of enantioselective catalysis can be envisioned. Today, the exclusion of three-membered carbo- and heterocycles from the arsenal of the organic chemist is inconceivable.H. Heimgartner, Angew. Chem. 1991, 103, 271; Angew. Chem. Int. Ed. Engl. 1991, 30, 238.
    Additional Material: 6 Tab.
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