Identification of Alkoxy Radicals as Hydrogen Atom Transfer Agents in Ce-Catalyzed C–H Functionalization

Journal of the American Chemical Society, Год журнала: 2022, Номер 145(1), С. 359 - 376

Опубликована: Дек. 20, 2022

The intermediacy of alkoxy radicals in cerium-catalyzed C–H functionalization via H-atom abstraction has been unambiguously confirmed. Catalytically relevant Ce(IV)–alkoxide complexes have synthesized and characterized by X-ray diffraction. Operando electron paramagnetic resonance transient absorption spectroscopy experiments on isolated pentachloro Ce(IV) alkoxides identified as the sole heteroatom-centered radical species generated ligand-to-metal charge transfer (LMCT) excitation. Alkoxy-radical-mediated hydrogen atom (HAT) verified kinetic analysis, density functional theory (DFT) calculations, reactions under strictly chloride-free conditions. These experimental findings establish critical role Ce-LMCT catalysis definitively preclude involvement chlorine radical. This study also reinforced necessity a high relative ratio alcohol vs Ce for selective alkoxy-radical-mediated HAT, seemingly trivial changes can lead to drastically different mechanistic pathways. Importantly, previously proposed radical–alcohol complex, postulated explain alkoxy-radical-enabled selectivities this system, examined scrutiny ruled out regioselectivity studies, experiments, high-level calculations. Moreover, peculiar selectivity generation LMCT homolysis heteroleptic analyzed back-electron (BET) may regulated efficiency formation ligand-centered radicals.

Язык: Английский

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Tetrachlorophthalimides as Organocatalytic Acceptors for Electron Donor–Acceptor Complex Photoactivation

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(20), С. 8914 - 8919

Опубликована: Май 13, 2022

Excitation of photoactive electron donor-acceptor (EDA) complexes is an effective way to generate radicals. Applications in a catalytic regime typically use donors. Herein, we report that readily available electron-poor tetrachlorophthalimides can act as organocatalytic acceptors trigger the formation EDA with variety radical precursors not amenable previous methods. visible light generates carbon radicals under mild conditions. The versatility this complex platform allowed us develop mechanistically distinct reactions, including combination cobalt-based system. Quantum yield measurements established closed cycle operational, which hints at ability turn over and govern each cycle.

Язык: Английский

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A general electron donor–acceptor complex enabled cascade cyclization of alkynes to access sulfur-containing heterocycles

Green Chemistry, Год журнала: 2023, Номер 25(8), С. 3111 - 3116

Опубликована: Янв. 1, 2023

A general visible light-promoted and electron–donor–acceptor complex-enabled cascade reaction of alkynes to produce functionalized sulfur-containing heterocycles under photocatalyst-, base-, oxidant- metal-free conditions was developed.

Язык: Английский

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Recent Advances in C–H Functionalisation through Indirect Hydrogen Atom Transfer

Molecules, Год журнала: 2023, Номер 28(16), С. 6127 - 6127

Опубликована: Авг. 18, 2023

The functionalisation of C–H bonds has been an enormous achievement in synthetic methodology, enabling new retrosynthetic disconnections and affording simple equivalents for synthons. Hydrogen atom transfer (HAT) is a key method forming alkyl radicals from substrates. Classic reactions, including the Barton nitrite ester reaction Hofmann–Löffler–Freytag reaction, among others, provided early examples HAT. However, recent developments photoredox catalysis electrochemistry have made HAT powerful tool capable introducing wide range functional groups into bonds. Moreover, greater mechanistic insights stimulated development increasingly site-selective protocols. Site-selectivity can be achieved through tuning electron density at certain using additives, judicious choice reagent, solvent system. Herein, we describe latest methods functionalizing C–H/Si–H/Ge–H indirect between 2018–2023, as well critical discussion reagents, aspects, substrate scopes, background contexts

Язык: Английский

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Catalytic acceptorless complete dehydrogenation of cycloalkanes

Nature Communications, Год журнала: 2025, Номер 16(1)

Опубликована: Янв. 9, 2025

Язык: Английский

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Atroposelective Electrophilic Sulfenylation ofN‐Aryl Aminoquinone Derivatives Catalyzed by Chiral SPINOL‐Derived Sulfide

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(42)

Опубликована: Авг. 30, 2022

Atroposelective electrophilic sulfenylation of N-aryl aminoquinone derivatives has been achieved for the first time. This transformation is enabled by a new chiral 6,6'-disubstituted SPINOL-derived sulfide catalyst, which was synthesized and then successfully explored catalyzing enantioselective reactions. Various axially sulfur-containing diarylamine were readily obtained in moderate to excellent yields with enantioselectivities. A class relatively flexible stereogenic C-N axes easily constructed. The experimental results computational study suggested that an intramolecular N-H⋅⋅⋅S hydrogen bond important stability axis, consistent our hypothesis. Density functional theory calculations revealed origin atroposelectivity underscored importance catalyst rigidity this reaction.

Язык: Английский

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Thiols as Powerful Atom Transfer Catalyst: Opportunities in Photoredox‐Mediated Reactions

Advanced Synthesis & Catalysis, Год журнала: 2023, Номер 365(14), С. 2299 - 2309

Опубликована: Июнь 12, 2023

Abstract The employing visible light to drive organic transformations is the most promising choice meet needs for green synthesis, in which reactions promoted by may provide a more efficient and greener method. Currently, abundant methods activation functionalization of reaction substrates have relied on direct single‐electron transfer (SET) between excited photocatalyst substrates, these wonderful works were summarized docoumented many reviews. As complement above reactions, photoredox‐mediated atom (photocatalyst‐to‐HAT catalyst‐to‐substrates) generate radical species are showing an explosively growing trend. In this review, we highlight recent significant developments rapidly area, mainly focusing photoinduced base‐to‐substrates charge reactions.

Язык: Английский

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Photochemical halogen-bonding assisted carbothiophosphorylation reactions of alkenyl and 1,3-dienyl bromides

Chemical Science, Год журнала: 2023, Номер 14(44), С. 12767 - 12773

Опубликована: Янв. 1, 2023

Herein, we present a synthetic procedure for the facile and general preparation of novel S-alkenyl dienyl phosphoro(di)thioates first time. Extensive mechanistic investigations support that reactions rely on photochemical excitation halogen-bonding complex, formed with phosphorothioate salt an alkenyl or bromide, which light-induced fragmentation leads to formation desired products through radical-based pathway. The substrate scope is broad exhibits wide functional group tolerance in final compounds, including molecules derived from natural products, all unknown potentially interesting biological properties. Eventually, very efficient continuous flow protocol was developed upscale these reactions.

Язык: Английский

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Photocatalytic C–N bond construction toward high-value nitrogenous chemicals

Chemical Communications, Год журнала: 2023, Номер 59(97), С. 14341 - 14352

Опубликована: Янв. 1, 2023

This review focuses on potential photocatalytic protocols developed for the construction of robust carbon–nitrogen bonds in discrepant activation environments to produce high-value nitrogenous chemicals.

Язык: Английский

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Thiobenzoic Acid-Catalyzed Cα–H Cross Coupling of Benzyl Alcohols with α-Ketoacid Derivatives

Organic Letters, Год журнала: 2024, Номер 26(25), С. 5285 - 5289

Опубликована: Июнь 13, 2024

The C-H alkylation of benzyl alcohols with α-ketoacid derivatives was achieved in the presence thiobenzoic acid or without Ru Ir photoredox catalysts. serves as a photoexcited single-electron reducing reagent and hydrogen atom transfer catalyst, while addition metal catalyst assists electron improves reaction efficiency. Various functional groups were tolerant conditions, sterically hindered diols produced good to high yield.

Язык: Английский

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