Detection and characterization of radical cations produced by one-electron chemical and electrochemical oxidations of organocobalt compounds

Halpern, Jack; Chan, Man-Sheung; Hanson, J. C.; Roche, Thomas S.; Topich, J.

doi:10.1021/ja00839a072

Cited by 94 publications

(27 citation statements)

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“…For example, semi-pinacol rearrangement of a cyclobutane-containing allylic alcohol 9 was achieved, furnishing the ring-expansion product 10 in good yield. An intramolecular hydroarylation reaction was demonstrated (12). Cyclization at the -position of an amide likely proceeded via a radical rather than a cationic intermediate, which is in line with Vanderwal's proposal on HAT-initiated oxidative polyene cyclization.…”

supporting

confidence: 82%

“…[11] In VB12-related systems, cationic organocobalt(IV) complexes have been known since 1970s (Figure 1b). [12] Their organometallic radical cation nature makes them susceptible to nucleophilic displacement at the alkyl ligand. [13] This was recently leveraged in a series of HAT-initiated oxidative hydrofunctionalization reactions using stoichiometric chemical oxidants such as N-fluoropyridiniums, hypervalent iodine reagents and persulfates.…”

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confidence: 99%

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Electrocatalytic Oxidative Hydrofunctionalization Reactions of Alkenes via Co(II/III/IV) Cycle

Yang

Nie

Liu

et al. 2021

Preprint

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Here we disclose a general and versatile Co(II/III/IV) electrocatalytic platform for alkene functionalization. Driven by electricity, a set of the oxidative hydrofunctionalization reactions initiated by hydrogen atom transfer were demonstrated without the need for stochiometric chemical oxidants. The scope of the reactions encompasses hydroalkoxylation, hydroacyloxylation, hydroarylation, semi-pinacol rearrangement, and deallylation. Mechanistic studies and stereochemical evidence support an ECEC process involving an electrochemically-generated organocobalt(IV) intermediate. This work presents an example of reactivity space expansion in electrocatalysis of VB12-systems by going beyond the common oxidation states of Co(I/II/III).

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confidence: 82%

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confidence: 99%

Electrocatalytic Oxidative Hydrofunctionalization Reactions of Alkenes via Co(II/III/IV) Cycle

Yang

Nie

Liu

et al. 2021

Preprint

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“…The addition of this amidyl radical (D) to alkene then gave rise to a carbon-centered radical (E). Followed by a RPC process, a carbocation (or partial positive charge) species (F) , underwent nucleophilic substitution by fluoride (path a) to afford the desired aminofluorination product (H) and, meanwhile, regenerated the cobalt catalyst to turn over the catalytic cycle. Alternatively, aminofluoride (H) could also be generated via a radical transfer process (path b) between the alkyl radical (E) and cobalt(III) fluoride (C).…”

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confidence: 99%

Cobalt-Catalyzed Divergent Aminofluorination and Diamination of Styrenes with N-Fluorosulfonamides

et al. 2021

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A cobalt-catalyzed aminofluorination reaction of styrenes with N-fluorosulfonamides serving as both the amination and fluorination agents has been developed. The switch of selectivity in this catalytic reaction from aminofluorination to diamination could be easily achieved by the addition of 1.0 equiv of PPh3. Both transformations tolerated a wide array of substrates under mild reaction conditions.

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“…This elementary step regenerates the Co(II) precatalyst, necessitating the stoichiometric use of oxidant and silane. These postulations are supported by pioneering work by Halpern and others describing the formation − and ensuing reactivity − of alkyl–Co(IV) complexes.…”

Section: Metal-hydride Hydrogen Atom Transfermentioning

confidence: 81%

Catalytic Asymmetric Hydroalkoxylation of C–C Multiple Bonds

et al. 2021

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Asymmetric hydroalkoxylation of alkenes constitutes a redox-neutral and 100% atom-economical strategy toward enantioenriched oxygenated building blocks from readily available starting materials. Despite their great potential, catalytic enantioselective additions of alcohols across a C–C multiple bond are particularly underdeveloped, especially compared to other hydrofunctionalization methods such as hydroamination. However, driven by some recent innovations, e.g., asymmetric MHAT methods, asymmetric photocatalytic methods, and the development of extremely strong chiral Brønsted acids, there has been a gratifying surge of reports in this burgeoning field. The goal of this review is to survey the growing landscape of asymmetric hydroalkoxylation by highlighting exciting new advances, deconstructing mechanistic underpinnings, and drawing insight from related asymmetric hydroacyloxylation and hydration. A deep appreciation of the underlying principles informs an understanding of the various selectivity parameters and activation modes in the realm of asymmetric alkene hydrofunctionalization while simultaneously evoking the outstanding challenges to the field moving forward. Overall, we aim to lay a foundation for cross-fertilization among various catalytic fields and spur further innovation in asymmetric hydroalkoxylations of C–C multiple bonds.

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Detection and characterization of radical cations produced by one-electron chemical and electrochemical oxidations of organocobalt compounds

Cited by 94 publications

References 0 publications

Electrocatalytic Oxidative Hydrofunctionalization Reactions of Alkenes via Co(II/III/IV) Cycle

Electrocatalytic Oxidative Hydrofunctionalization Reactions of Alkenes via Co(II/III/IV) Cycle

Cobalt-Catalyzed Divergent Aminofluorination and Diamination of Styrenes with N-Fluorosulfonamides

Catalytic Asymmetric Hydroalkoxylation of C–C Multiple Bonds

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