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    The origin of remarkable chromatographic differences in novel azulenyl-1,5-diols and synthesis and use of phosphinine and phosphabarrelene ligands for asymmetric catalysis.

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    Date
    2014-09-05
    Author
    Horgen, Dana Ann
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    Abstract
    The synthesis, characterization and analysis of novel chiral molecules advance many areas of synthetic organic chemistry, both industrially and academically. This work touches on three of the major methods for obtaining enantiomerically pure compounds. Based on the observation of a remarkably large difference in the silica TLC mobility of a pair of azulene 1,5-diol diastereomers, a series of such azulene 1,5-diols were prepared. Every pair of diastereomers was especially well separated, and X-ray crystallography revealed a conformational explanation of the large differences in mobility. The separation of the diol enantiomers was then studied on two chiral HLPC columns. The enantiomers were well-resolved, the separation appearing to benefit from the presence of the azulene ring. In addition, the more polar diastereomers on silica TLC gave dramatically better enantiomer separations on a Chiralcel-OD-H column. Very few chiral phosphinine and phosphabarrelene ligands have been reported in the literature but have shown promise as good ligands for asymmetric catalysis. Our group had previously synthesized a C₂-symmetric chiral bis-camphorphosphinine and the derived bis-camphorphosphabarrelene but neither had been tested as ligands for hydroformylation. In this work, optimization of the synthesis of these two compounds was undertaken. In addition, modifications to the structure of these molecules that incorporated electron donating (N,N-dimethylaminophenyl-) or electron withdrawing (trifluoromethyl-) substituents were made in an attempt to affect the electronic nature of the phosphorus atom. Steric modifications were also done to create a more hindered environment around the phosphorus atom. The activity and selectivity of bis-camphorphosphinine, bis-camphorphosphabarrelene and other chiral phosphinine molecules serving as ligands in the rhodiumcatalyzed hydroformylation of styrene were compared to other phosphorus ligands recently published in the literature. All of these ligands gave complexes that have moderate activity with good regioselectivity but very little enantioselectivity. Therefore, more tuning of these ligands' properties need to be done in order to achieve the activity and selectivity of other chiral monodentate-ligands. The bis-camphorphosphabarrelene was also a successful organocatalyst of the Baylis-Hillman reaction, showing its versatility in both metal-catalyzed and metal-free catalysis.
    URI
    http://hdl.handle.net/2104/9161
    Department
    Chemistry and Biochemistry.
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    Copyright © Baylor® University All rights reserved. Legal Disclosures.
    Baylor University Waco, Texas 76798 1-800-BAYLOR-U
    Baylor University Libraries | One Bear Place #97148 | Waco, TX 76798-7148 | 254.710.2112 | Contact: libraryquestions@baylor.edu
    If you find any errors in content, please contact librarywebmaster@baylor.edu
    DSpace software copyright © 2002-2016  DuraSpace
    Contact Us | Send Feedback
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