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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 580-585 
    ISSN: 0899-0042
    Keywords: asymmetric dihydroxylation ; enantiomeric excesses ; polymerization ; chiral separation ; optically active diols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new insoluble polymer containing a Cinchona alkaloid derivative has been synthesized and used as chiral ligand in the heterogeneous enantioselective dihydroxylation of olefins. It is shown that the enantioselectivity of the optically active diols obtained from both aliphatic and aromatic substrates is always comparable to that observed in the homogeneous phase under the same reaction conditions. A method for evaluating the enantiomeric excesses of the optically active products is also described. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 0899-0042
    Keywords: chromatography ; chirality ; chiral recognition ; β-aminoalcohols ; stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three chiral stationary phases, obtained by derivatizing γ-mercaptopropylsilanized silica gel with quinine, quinidine, and cinchonidine, have been employed in the resolution of N-acyl derivatives of β-hydroxyphenethylamines. The use of circular dichroism for detection and NMR analysis of analyte-selector mixtures provides an experimental basis for preliminary assignment of a recognition mechanism.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Polymerisation von optisch aktiven α-Olefinen, wie (R)-4-Phenyl-1-hexen (1) und (S)-5-Phenyl-1-hepten (2), mit ZIEGLER-NATTA-Katalysatoren wie TiCl3/(„ARA“) oder VCl4/Al[CH2CH(CH3)2] wird untersucht. 2 liefert Polymere, die bei Raumtemperatur amorph sind; kein Beweis sterischer Ordnung wird durch IR-Untersuchung erhalten, aber 1H-NMR-Spektren zeigen die Anwesenheit einer partiellen Stereoregularität an. Im Gegensatz dazu liefert 1 Polymere, die in siedenden Lösungsmitteln vorwiegend unlöslich sind und die nach den Röntgendiagrammen kristallin sind, was auf das Vorhandensein von isotaktischen Strukturen hinweist. Durch die Copolymerisation von 1 mit 4-Methyl-1-penten werden kristalline Polymere erhalten, die wahrscheinlich statistische coisotaktische Struktur besitzen, wie mit Hilfe der Röntgendiagramme der IR-Spektren und des Drehungsvermögens gezeigt wird.
    Notes: The polymerization of optically active phenyl-α-olefins, such as (R)-4-phenyl-1-hexene (1) and (S)-5-phenyl-1-heptene (2), has been performed by TiCl3/(“ARA”) or VCl4/Al[CH2CH(CH3)2]3 catalyst. 2 gives polymers which are amorphous at room temperature; no evidence of stereoregularity is obtained by IR investigation, whereas 1H-NMR spectra seem to give some indication of steric order. By contrast, the polymers from 1, which are largely insoluble in boiling solvents, are crystalline at X-ray examination according to an isotactic structure. The copolymerization of 1 with 4-methyl-1-pentene (3) gives statistical copolymers which appear to be coisotactic. This is confirmed by crystallinity at X-ray examination, IR and optical activity data.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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