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    Syntheses of Functionalized Benzylic Compounds: Development of Palladium-Catalyzed Decarboxylative Benzylation Reactions

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    Issue Date
    2012-08-31
    Author
    Torregrosa, Robert Ryan P.
    Publisher
    University of Kansas
    Format
    246 pages
    Type
    Dissertation
    Degree Level
    Ph.D.
    Discipline
    Chemistry
    Rights
    This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
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    Abstract
    Carbon-carbon bond formation between the benzyl carbon and a functional group is important in organic synthesis because majority of the compounds in the chemical literature contain aromatic cores appended with different functionalities in the benzyl carbon. These compounds are utilized in pharmaceuticals and medicinal chemistry. While current literature in Pd-catalyzed benzylations is increasingly becoming recognized, conventional methodologies require the use of toxic benzyl halides, stoichiometric bases and/or performed organometallics which not only generate benzyl compounds but also give side products and toxic metal wastes. Our research group has a long-standing interest using decarboxylation as a tool in constructing diverse compounds without the need of base and preformed organometallics. Previously applied in the synthesis of functionalized allylic compounds from allyl esters, we envisioned to utilize this tool towards the synthesis of functionalized benzylic compounds from benzyl esters. We thought that it would be feasible and ideal to perform decarboxylative benzylation (DcB) based from well-explored decarboxylative allylation (DcA) methodology. Indeed, we were able to show that Pd-catalyzed DcB was an indispensable tool in synthesizing functionalized benzylic compounds in good to high yields. This was shown in the syntheses of benzyl ketones and benzyl alkynes. In the DcB of ketones, simple and benzo-fused β-ketoesters underwent decarboxylation affording benzyl ketones in good to high yields. DcB was also regiospecific, the kinetically preformed enolate did not undergo thermodynamic isomerization resulting to direct functionalization to the carbon next to the carboxylate group where it was once located. In addition to naphthyl and simple benzyls, heteroaromatics were also used as coupling partners with enolate. The nature of substituents in the ring and its position from the benzyl moiety affected benzylation. Depending on the nature of heterocycle, regioselective benzylation occurred resulting in formation of C-benzylation ketone, C-arylation ketone, or O-benzylation enol ether. The utility of DcB methodology was also used towards the synthesis of Nabumetone. In the DcB of alkynes, simple and benzo-fused propiolates underwent decarboxylation to generate benzyl alkynes in good to high yields. The use of biphenyl derived ligand was crucial in the synthesis of simple benzyl alkynes. The benzylic carbon in diaryls and heterocycles can also be used as coupling partners with alkynes.
    URI
    http://hdl.handle.net/1808/10266
    Collections
    • Chemistry Dissertations and Theses [336]
    • Dissertations [4475]

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    785-864-8983
    KU Libraries
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    785-864-8983

    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
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    Contact KU ScholarWorks
    785-864-8983
    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    785-864-8983

    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    Image Credits
     

     

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