Enantioselective Hydroamination of Alkenes with Sulfonamides Enabled by Proton-Coupled Electron Transfer

Roos, Casey B.; Demaerel, Joachim; Graff, David; Knowles, Robert R.

doi:10.26434/chemrxiv.11796702

Cited by 3 publications

(3 citation statements)

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“…The addition of 9 further displayed a second irreversible oxidation at 0.70 V vs Fc/Fc + (green line). We performed a background scan to explore the possibility of direct substrate oxidation to generate nitrogencentered radicals via sulfonamide oxidation 47,[49][50][51]74 or radical cations via alkene oxidation. 75−79 However, this scan displays a fully non-Faradaic capacitive response, invalidating the aforementioned pathways as possible mechanisms (brown line).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Electrocatalytic Access to Azetidines via Intramolecular Allylic Hydroamination: Scrutinizing Key Oxidation Steps through Electrochemical Kinetic Analysis

et al. 2023

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Azetidines are prominent structural scaffolds in bioactive molecules, medicinal chemistry, and ligand design for transition metals. However, state-of-the-art methods cannot be applied to intramolecular hydroamination of allylic amine derivatives despite their underlying potential as one of the most prevalent synthetic precursors to azetidines. Herein, we report an electrocatalytic method for intramolecular hydroamination of allylic sulfonamides to access azetidines for the first time. The merger of cobalt catalysis and electricity enables the regioselective generation of key carbocationic intermediates, which could directly undergo intramolecular C–N bond formation. The mechanistic investigations including electrochemical kinetic analysis suggest that either the catalyst regeneration by nucleophilic cyclization or the second electrochemical oxidation to access the carbocationic intermediate is involved in the rate-determining step (RDS) of our electrochemical protocol and highlight the ability of electrochemistry in providing ideal means to mediate catalyst oxidation.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Electrocatalytic Access to Azetidines via Intramolecular Allylic Hydroamination: Scrutinizing Key Oxidation Steps through Electrochemical Kinetic Analysis

et al. 2023

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“…ppy) 2 (5,5′-dCF 3 bpy)]PF 6 (2 mol%) and a BINOL-derived phosphate (2.5 mol%). 23 These transformations were proposed to occur via N-centred radicals generated by PCET activation of sulfonamide N-H bonds. The H-bonding interaction between the neutral sulfonamidyl radical and the CPA generated in the PCET event was hypothesized to be the basis for asymmetric induction in the subsequent C-N bond-forming step, providing enantioenriched pyrrolidine products with up to 96% ee.…”

Section: Enantioselective Radical Additionmentioning

confidence: 99%

Cooperative photoredox and chiral hydrogen-bonding catalysis

et al. 2020

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“…The noncovalent interaction between an N-centered radical and a chiral phosphoric acid is central to the enantioselectivity in an intramolecular hydroamination reaction that was recently developed by Knowles' group. 33,34 In our work, we accidentally came across the formation of a noncovalent radical−water complex following our interest in the reactions of matrix isolated radicals, 35 where we aimed to produce the carboxymethyl radical 1 through flash vacuum pyrolysis of iodoacetic acid (2, Scheme 1). 36 The carboxymethyl radical is an interesting target by itself because it is assumed to play a role in the interstellar formation of the amino acid glycine 37 and has therefore been prepared by Y. P. Lee's lab in the reaction of hydrogen atoms with acetic acid in a para-H 2 matrix.…”

Section: ■ Introductionmentioning

confidence: 99%

A Metastable Ketenyl Radical–Water Complex from UV Photolysis of the Carboxymethyl Radical

Wagner

Bhagat

2023

J. Phys. Chem. A

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The unpaired electron impacts the binding between radicals and ordinary closed-shell molecules in noncovalent complexes. Conversely, the complexation partner can enhance, decrease, or even control the reactivity of the interacting radical. Previously, such radical−molecule (and especially radical−water) complexes were studied by controlled assembly of the interacting partners which mostly leads to formation of the thermodynamically most stable species. Here, we show that UV photolysis of the resonance-stabilized carboxymethyl radical isolated in a cryogenic argon matrix at 4 K leads to the intermediary formation of a metastable, noncovalent complex of the ketenyl radical with a water molecule. In this complex, the ketenyl radical binds water at its terminal carbon atom, although a more stable isomer exists in which water interacts with the C−H bond of the radical. Rigorous W1 theory computations confirm that the ketenyl radical is a stronger donor in C−H•••O interactions than ketene itself, while it performs comparably well as an acceptor. We propose that complex formation proceeds via an initial excited-state C−O bond breaking reaction in carboxymethyl under release of an OH radical, which is supported by multireference QD-NEVPT2 computations.

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Enantioselective Hydroamination of Alkenes with Sulfonamides Enabled by Proton-Coupled Electron Transfer

Cited by 3 publications

References 0 publications

Electrocatalytic Access to Azetidines via Intramolecular Allylic Hydroamination: Scrutinizing Key Oxidation Steps through Electrochemical Kinetic Analysis

Electrocatalytic Access to Azetidines via Intramolecular Allylic Hydroamination: Scrutinizing Key Oxidation Steps through Electrochemical Kinetic Analysis

Cooperative photoredox and chiral hydrogen-bonding catalysis

A Metastable Ketenyl Radical–Water Complex from UV Photolysis of the Carboxymethyl Radical

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