Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C–H Bonds Elaboration

Chemical Reviews, Год журнала: 2021, Номер 122(2), С. 1875 - 1924

Опубликована: Авг. 6, 2021

Direct photocatalyzed hydrogen atom transfer (d-HAT) can be considered a method of choice for the elaboration aliphatic C–H bonds. In this manifold, photocatalyst (PCHAT) exploits energy photon to trigger homolytic cleavage such bonds in organic compounds. Selective bond may achieved by judicious abstractor (key parameters are electronic character and molecular structure), as well reaction additives. Different classes PCsHAT available, including aromatic ketones, xanthene dyes (Eosin Y), polyoxometalates, uranyl salts, metal-oxo porphyrin tris(amino)cyclopropenium radical dication. The processes (mainly C–C formation) most cases carried out under mild conditions with help visible light. aim review is offer comprehensive survey synthetic applications d-HAT.

Язык: Английский

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Photocatalytic Late-Stage C–H Functionalization

Chemical Reviews, Год журнала: 2023, Номер 123(8), С. 4237 - 4352

Опубликована: Янв. 24, 2023

The emergence of modern photocatalysis, characterized by mildness and selectivity, has significantly spurred innovative late-stage C–H functionalization approaches that make use low energy photons as a controllable source. Compared to traditional strategies, photocatalysis paves the way toward complementary and/or previously unattainable regio- chemoselectivities. Merging compelling benefits with workflow offers potentially unmatched arsenal tackle drug development campaigns beyond. This Review highlights photocatalytic strategies small-molecule drugs, agrochemicals, natural products, classified according targeted bond newly formed one. Emphasis is devoted identifying, describing, comparing main mechanistic scenarios. draws critical comparison between established ionic chemistry photocatalyzed radical-based manifolds. aims establish current state-of-the-art illustrate key unsolved challenges be addressed in future. authors aim introduce general readership functionalization, specialist practitioners evaluation methodologies, potential for improvement, future uncharted directions.

Язык: Английский

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Strategies to Generate Nitrogen-centered Radicals That May Rely on Photoredox Catalysis: Development in Reaction Methodology and Applications in Organic Synthesis

Chemical Reviews, Год журнала: 2021, Номер 122(2), С. 2353 - 2428

Опубликована: Окт. 8, 2021

For more than 70 years, nitrogen-centered radicals have been recognized as potent synthetic intermediates. This review is a survey designed for use by chemists engaged in target-oriented synthesis. summarizes the recent paradigm shift access to and application of N-centered enabled visible-light photocatalysis. broadens streamlines approaches many small molecules because photocatalysis conditions are mild. Explicit attention paid innovative advances N–X bonds radical precursors, where X = Cl, N, S, O, H. clarity, key mechanistic data noted, available. Synthetic applications limitations summarized illuminate tremendous utility photocatalytically generated radicals.

Язык: Английский

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Radical C(sp3)–H functionalization and cross-coupling reactions

Nature Reviews Chemistry, Год журнала: 2022, Номер 6(6), С. 405 - 427

Опубликована: Май 17, 2022

Язык: Английский

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Photoelectrochemical asymmetric catalysis enables site- and enantioselective cyanation of benzylic C–H bonds

Nature Catalysis, Год журнала: 2022, Номер 5(10), С. 943 - 951

Опубликована: Окт. 10, 2022

Язык: Английский

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N-Functionalized Pyridinium Salts: A New Chapter for Site-Selective Pyridine C–H Functionalization via Radical-Based Processes under Visible Light Irradiation

Accounts of Chemical Research, Год журнала: 2022, Номер 55(20), С. 3043 - 3056

Опубликована: Сен. 27, 2022

ConspectusThe radical-mediated C–H functionalization of pyridines has attracted considerable attention as a powerful tool in synthetic chemistry for the direct bonds pyridine scaffold. Classically, methods functionalized often involve Minisci-type reactions under strongly acidic conditions. However, site-selective unbiased systems been long-standing challenge because scaffold contains multiple competing reaction sites (C2 vs C4) to intercept free radicals. Therefore, prefunctionalization is required avoid issues observed with formation mixture regioisomers and overalkylated side products.Recently, N-functionalized pyridinium salts have attracting organic promising radical precursors surrogates. The notable advantage lies their ability enhance reactivity selectivity synthetically useful acid-free This approach enables exquisite regiocontrol nonclassical at C2 C4 positions mild conditions, which are suitable late-stage bioactive molecules greater complexity diversity. Over past five years, variety fascinating applications developed using various types visible light In addition, new platform alkene difunctionalization appropriately designed N-substituted bifunctional reagents reported, offering an innovative assembly process complex architectures. Intriguingly, strategies involving light-absorbing electron donor–acceptor (EDA) complexes between electron-rich donors further open up photocatalyst-free Furthermore, we enantioselective afford enantioenriched bearing through single-electron N-heterocyclic carbene (NHC) catalysis.Herein, provide broad overview our recent contributions development summarize cornerstones that successfully employ these major advances field systematically categorized on basis pyridines' N-substituent, N–X (X = O, N, C, SO2CF3), its patterns. identification activation modes mechanistic aspects discussed by providing representative each paradigm. We hope this Account will inspire interest continued innovation exploration transformations.

Язык: Английский

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Diboron(4)‐Catalyzed Remote [3+2] Cycloaddition of Cyclopropanes via Dearomative/Rearomative Radical Transmission through Pyridine

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(52)

Опубликована: Ноя. 8, 2022

Abstract Ring structures such as pyridine, cyclopentane or their combinations are important motifs in bioactive molecules. In contrast to previous cycloaddition reactions that necessitated a directly bonded initiating functional group, this work demonstrated novel through‐(hetero)arene radical transmission concept for selective activation of remote bond. An efficient, metal‐free and atom‐economical [3+2] between 4‐pyridinyl cyclopropanes alkenes alkynes has been developed modular synthesis pyridine‐substituted cyclopentanes, cyclopentenes bicyclo[2.1.1]hexanes difficult access using known methods. This complexity‐building reaction was catalyzed by very simple inexpensive diboron(4) compound took place via dearomative/rearomative processes. The substrate scope broad more than 100 new compounds were prepared generally high yields. Mechanistic experiments density function theory (DFT) investigation supported relay catalytic cycle involving alkylidene dihydropyridine intermediates boronyl transfer.

Язык: Английский

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Resurgence and advancement of photochemical hydrogen atom transfer processes in selective alkane functionalizations

Chemical Science, Год журнала: 2023, Номер 14(25), С. 6841 - 6859

Опубликована: Янв. 1, 2023

The selective functionalization of alkanes has long been recognized as a prominent challenge and an arduous task in organic synthesis. Hydrogen atom transfer (HAT) processes enable the direct generation reactive alkyl radicals from feedstock have successfully employed industrial applications such methane chlorination process,

Язык: Английский

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Decatungstate-photocatalyzed direct acylation of N-heterocycles with aldehydes

Green Chemistry, Год журнала: 2024, Номер 26(12), С. 7331 - 7336

Опубликована: Янв. 1, 2024

A novel photocatalytic acylation strategy was developed harnessing tetrabutylammonium decatungstate (TBADT) as a hydrogen atom transfer (HAT) photocatalyst to facilitate the direct coupling of aldehydes with N-heterocycles at ambient temperature.

Язык: Английский

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Hydroalkylation of Unactivated Olefins via Visible-Light-Driven Dual Hydrogen Atom Transfer Catalysis

Journal of the American Chemical Society, Год журнала: 2021, Номер 143(29), С. 11251 - 11261

Опубликована: Июль 16, 2021

Radical hydroalkylation of olefins enabled by hydrogen atom transfer (HAT) catalysis represents a straightforward means to access C(sp3)-rich molecules from abundant feedstock chemicals without the need for prefunctionalization. While Giese-type activated initiated HAT hydridic carbon-hydrogen bonds is well-precedented, unactivated in similar fashion remains elusive, primarily owing lack general methods overcome inherent polarity-mismatch this scenario. Here, we report use visible-light-driven dual achieve goal, where catalytic amounts an amine-borane and situ generated thiol were utilized as abstractor donor, respectively. The reaction completely atom-economical exhibits broad scope. Experimental computational studies support proposed mechanism suggest that hydrogen-bonding between substrates beneficial improving efficiency.

Язык: Английский

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