Superoxide-Facilitated Cathodic Cleavage of 1,1-Diphenyl Ketones

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The cathodic conversion of 1,1-diphenylacetone (1) to benzophenone (2) was investigated. Through divided-cell electrolyses, cyclic voltammetry, and reactions with authentic superoxide, it was demonstrated that molecular oxygen is likely reduced to the superoxide anion at the cathode, where it proceeds to react with 1 to form an α-hydroperoxy ketone intermediate. Nucleophilic attack at the carbonyl by a second molecule of superoxide facilitates cleavage of the carbon-carbonyl bond to afford 2. Analogously, it was determined through mechanistic studies that α-substituted 1,1-diphenyl ketones undergo α-cleavage of the acyl group in a remarkably mild cathodic reaction. This transformation is postulated to occur via reduction of oxygen to superoxide, which forms a hydroperoxy anion that then attacks the carbonyl to give a tetrahedral intermediate. As the intermediate collapses to reform the carbonyl, the carbon-carbonyl bond is cleaved to yield the hydrocarbon product. Observed superoxide-facilitated α-cleavage offers an explanation for the previously-described cathodic cleavage of α-alkoxyaldehydes to benzhydryl alkyl ethers. The significant structural changes that are afforded by the mild cathodic reactions discussed here demonstrate the synthetic capabilities of organic electrochemistry.

    Item Description
    Name(s)
    Author: Tsui, Elaine
    Thesis advisor: Fry, Albert
    Date
    April 15, 2015
    Extent
    111 pages
    Language
    eng
    Genre
    Physical Form
    electronic
    Discipline
    Rights and Use
    In Copyright – Non-Commercial Use Permitted
    Digital Collection
    PID
    ir:363