8 research outputs found

    Advances in Oxoammonium-Salt Mediated Transformations: Mechanistic Investigations, Oxidative Functionalization, and Photoredox Catalysis

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    The development of innovative methodologies enables the synthetic chemist to construct molecules in new and more efficient ways. Computational modeling has allowed for mechanistic insights and often guided experimental projects, including several oxidative functionalization reactions. Photoredox catalysis has been employed as a new method to access the oxoammonium cation scaffold and its reactivity. These areas are not only sought after by the wider chemical community, but also represent a central theme in this work, namely utilizing synthetically advantageous chemical transformations to forge new bonds in an efficient and environmentally friendly method

    Enantioselective Transition-Metal Catalysis via Anion Binding with Chiral Hydrogen-Bond Donors

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    Asymmetric transition-metal catalysis represents a powerful strategy for accessing enantiomerically enriched molecules. Here, we report a new approach for inducing enantioselectivity in transition-metal-catalyzed reactions that relies on neutral hydrogen-bond donors (HBDs) that bind anions of transition-metal complexes to achieve enantiocontrol and rate enhancement through ion pairing in concert with other noncovalent interactions. A cooperative anion-binding effect of a chiral bis-thiourea HBD is demonstrated to lead to high enantioselectivity (up to 99% enantiomeric excess) in intramolecular ruthenium-catalyzed propargylic substitution reactions. Experimental and computational mechanistic studies reveal the attractive interactions between electron-deficient arene components of the HBD and the metal complex that underlie enantioinduction and the acceleration effect

    Accessing <i>N</i>‑Acyl Azoles via Oxoammonium Salt-Mediated Oxidative Amidation

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    An operationally simple, robust, metal-free approach to the synthesis of <i>N</i>-acyl azoles from both alcohols and aldehydes is described. Oxidative amidation is facilitated by a commercially available organic oxidant (4-acetamido-2,2,6,6-tetramethyl­piperidine-1-oxoammonium tetrafluoro­borate) and proceeds under very mild conditions for an array of structurally diverse substrates. Tandem reactions of these activated amides, such as transamidation and esterification, enable further elaboration. Also, the spent oxidant can be recovered and used to regenerate the oxoammonium salt

    Toward a Unified Mechanism for Oxoammonium Salt-Mediated Oxidation Reactions: A Theoretical and Experimental Study Using a Hydride Transfer Model

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    A range of oxoammonium salt-based oxidation reactions have been explored computationally using density functional theory (DFT), and the results have been correlated with experimentally derived trends in reactivity. Mechanistically, most reactions involve a formal hydride transfer from an activated C–H bond to the oxygen atom of the oxoammonium cation. Several new potential modes of reactivity have been uncovered and validated experimentally
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