Skip to content
University of Maryland LibrariesDigital Repository at the University of Maryland
    • Login
    View Item 
    •   DRUM
    • Theses and Dissertations from UMD
    • UMD Theses and Dissertations
    • View Item
    •   DRUM
    • Theses and Dissertations from UMD
    • UMD Theses and Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    INTRAMOLECULAR CARBON-NITROGEN COUPLING FROM ISOLATED MONOHYDROCARBYL PALLADIUM(IV) COMPLEXES PREPARED USING H2O2 AS TERMINAL OXIDANT

    View/Open
    Abada_umd_0117E_17993.pdf (11.65Mb)
    (RESTRICTED ACCESS)
    No. of downloads: 0

    Date
    2017
    Author
    Abada, Elikplim
    Advisor
    Vedernikov, Andrei N
    DRUM DOI
    https://doi.org/10.13016/M2827G
    Metadata
    Show full item record
    Abstract
    Carbon-nitrogen coupling is achieved traditionally by coupling of aryl halides and amines through a Pd(0)/Pd(II) catalytic cycle (Buchwald-Hartwig amination). A newer, more atom-economical approach to the synthesis of amines is based on oxidative C-H amination. Recent studies of C-H amination propose the involvement of Pd(II)/Pd(IV) catalytic cycle through a C-H activation step. This work seeks to develop new stoichiometric and catalytic ways of forming C-N bonds through a Pd(II)/Pd(IV) cycle using H2O2 as terminal oxidant. In this effort, di-2-pyridylketone(dpk) ligated palladacycles were synthesized, oxidized with H2O2, and the reductive elimination of the high oxidation state Pd(IV, d6) containing species monitored. N-R-2-aminobiphenyl – derived substrates with electron donating groups (R = H, Me, Et) readily form carbazoles at room temperature without formation of appreciable amounts of intermediates. The use of electron withdrawing group (R = COCH3, COCF3, SO2CH3, SO2CF3) slows down the reaction for intermediates to be observed and isolated. Mechanistic studies of the first ever C(sp2)-N reductive elimination from an isolated Pd(IV, d6) intermediate was observed to be accelerated in the presence of acids. Reductive elimination is proposed to occur from a 6-coordinate Pd(IV, d6) center. The dpk ligated Pd(IV, d6) palladacycles derived from 4-X-substituted N-SO2CF3-2-tert-butylaniline (X = H, Br, I), reductively eliminate the corresponding C(sp3)-N coupled products, 5-X-substituted indolines in high yield only in the presence of halohalic acids (HCl, HBr and HI). This confirms the importance of a proton source and a nucleophilic anion for this process to take place. Reductive elimination is proposed to occur through several competing pathways based on the fractional order of reaction with respect to [Br-] in solution. Catalytic heterocyclization reaction was achieved using H2O2 with N-acetyl-2-aminobiphenyl to form N-acetylcarbazole with yields dependent on temperature and rate of addition of H2O2.
    URI
    http://hdl.handle.net/1903/19482
    Collections
    • Chemistry & Biochemistry Theses and Dissertations
    • UMD Theses and Dissertations

    DRUM is brought to you by the University of Maryland Libraries
    University of Maryland, College Park, MD 20742-7011 (301)314-1328.
    Please send us your comments.
    Web Accessibility
     

     

    Browse

    All of DRUMCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsThis CollectionBy Issue DateAuthorsTitlesSubjects

    My Account

    LoginRegister
    Pages
    About DRUMAbout Download Statistics

    DRUM is brought to you by the University of Maryland Libraries
    University of Maryland, College Park, MD 20742-7011 (301)314-1328.
    Please send us your comments.
    Web Accessibility