Radical NHC Catalysis

ACS Catalysis, Год журнала: 2022, Номер 12(19), С. 11984 - 11999

Опубликована: Сен. 19, 2022

Radical/radical cross-coupling reactions represent an efficient and straightforward approach for the construction of chemical bonds accordingly have drawn increasing attention over past decades. In order to achieve synthetically useful transformations, a persistent radical should be coupled with transient in accordance effect (PRE). However, known radicals outnumber by far types free radicals, which limits widespread application PRE, until today. Thus, development between has been focus, meanwhile transition-metal catalysis successfully implemented artificially prolong lifetimes, allowing their utilization formal radical/radical cross-couplings. Complementary research field recently uncovered that organocatalytically generated NHC-derived ketyl are type catalytically radicals. NHC-catalyzed transformations aldehydes carboxylic acid derivatives enabled disclosure ever-increasing number interesting reactions, different from traditional ionic processes, offering otherwise inaccessible activation modes. These discoveries opened door NHC organocatalysis manipulation reactions. Due its obvious potential synthetic organic chemistry, it is timely provide perspective on this emerging field.

Язык: Английский

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Photoinduced Acylations Via Azolium-Promoted Intermolecular Hydrogen Atom Transfer

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(3), С. 1535 - 1541

Опубликована: Янв. 10, 2023

Photoinduced hydrogen atom transfer (HAT) has been developed as a powerful tool to generate synthetically valuable radical species. The direct photoexcitation of ketones known promote HAT or acyl radicals through Norrish-type pathways, but these modalities remain severely limited by side reactions. We report herein catalyst- and transition metal-free method for the acylation C-H bonds that leverages unique properties stable, isolable azolium Specifically, salts are shown undergo an intermolecular regioselective upon LED irradiation with range substrates bearing active followed C-C bond formation afford ketones. Experimental computational studies support facile intersystem crossing access triplet diradical species selective radical-radical cross-coupling.

Язык: Английский

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Oxidative Radical NHC Catalysis: Divergent Difunctionalization of Olefins through Intermolecular Hydrogen Atom Transfer

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(44)

Опубликована: Сен. 9, 2022

Oxidative N-heterocyclic carbene (NHC) organocatalysis, typically leading to the formation of acyl azolium reactive intermediates, constitutes one most important activation strategies for NHC-catalyzed chemical transformations. Here, we report an unprecedented oxidative radical NHC catalysis by using peroxyester as external single-electron oxidant realize divergent difunctionalization olefins. The key success this chemistry is catalytic generation oxygen radicals that could trigger intermolecular hydrogen atom transfer activate inert C-H bonds, thereby enabling productive relay process. With protocol, commonly used general chemicals serve precursors allow efficient synthesis value-added products in a straightforward and cost-effective manner. Preliminary mechanistic investigations, including control experiments DFT calculations, shed light on organocatalytic reaction mechanism.

Язык: Английский

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Iminoacylation of Alkenes via Photoredox N-Heterocyclic Carbene Catalysis

Organic Letters, Год журнала: 2023, Номер 25(5), С. 855 - 860

Опубликована: Янв. 26, 2023

The iminoacylation of alkenes via photoredox N-heterocyclic carbene catalysis is developed with the employment alkene-tethered α-imino-oxy acids and acyl imidazoles. corresponding substituted 3,4-dihydro-2H-pyrroles were afforded in moderate to good yields high diastereoselectivities most cases. reaction involves 5-exo-trig radical cyclization an iminyl following coupling a ketyl from imidazole under NHC catalysis.

Язык: Английский

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Carbene‐Catalyzed Intermolecular Dehydrogenative Coupling of Aldehydes with C(sp³)−H Bonds

Angewandte Chemie International Edition, Год журнала: 2023, Номер 62(23)

Опубликована: Апрель 5, 2023

The development of catalyst-controlled methods for direct functionalization two distinct C-H bonds represents an appealing approach C-C formations in synthetic chemistry. Herein, we describe organocatalytic straightforward acylation C(sp3 )-H employing readily available aldehyde as "acyl source" involving dehydrogenative coupling aldehydes with ether, amine, or benzylic bonds. developed method affords a broad range ketones under mild conditions. Mechanistically, simple ortho-cyanoiodobenzene is essential the oxidative radical N-heterocyclic carbene catalysis to give ketyl and ) through rarely explored intermolecular hydrogen atom transfer pathway, rendering acylative high efficiency metal- light-free catalytic Moreover, prepared products show promising anti-bacterial activities that shall encourage further investigations on novel agrochemical development.

Язык: Английский

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Radical acylation: concepts, synthetic applications and directions

Organic Chemistry Frontiers, Год журнала: 2023, Номер 10(4), С. 1056 - 1085

Опубликована: Янв. 1, 2023

In this tutorial, reaction scopes, limitations and mechanisms of radical acylations are summarized discussed according to types catalytic systems.

Язык: Английский

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Recent Advances in the Functionalization of Remote C−H Bonds by Hofmann‐Löffler‐Freytag‐type Reactions

Advanced Synthesis & Catalysis, Год журнала: 2023, Номер 365(19), С. 3211 - 3226

Опубликована: Авг. 26, 2023

Abstract Nitrogen radicals are one of the most useful reactive intermediates for selective transposition via intramolecular hydrogen atom transfer (HAT). The Hofmann‐Löffler‐Freytag (HLF) reaction is a distinctive radical‐based approach in which nitrogen used remote C−H bond functionalization HAT. Due to its excellent regioselectivity and atomic economy, HLF represents new preparation valuable functional molecules. In this review, we provide brief overview recent research advances mediated HLF‐type reactions involving intermolecular cyclization, δ ‐site functionalization.

Язык: Английский

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N‐Heterocyclic carbene enabled functionalization of inert C(sp3)‐H bonds via hydrogen atom transfer (HAT) processes

Chemistry - A European Journal, Год журнала: 2024, Номер 30(47)

Опубликована: Авг. 2, 2024

Abstract Developing methods to directly transform C(sp 3 ) −H bonds is crucial in synthetic chemistry due their prevalence various organic compounds. While conventional protocols have largely relied on transition metal catalysis, recent advancements organocatalysis, particularly with radical NHC catalysis sparked interest the direct functionalization of “inert” for cross C−C coupling carbonyl moieties. This strategy involves selective cleavage generate key carbon radicals, often achieved via hydrogen atom transfer (HAT) processes. By leveraging bond dissociation energy (BDE) and polarity effects, HAT enables rapid diverse )−H substrates, such as ethers, amines, alkanes. mini‐review summarizes progress carbene organocatalytic inert enabled by processes, categorizing them into two sections: 1) C−H involving acyl azolium intermediates; 2) reductive Breslow intermediates.

Язык: Английский

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Remote C(sp³)–H heteroarylation of N-fluorocarboxamides with quinoxalin-2(1H)-ones under visible-light-induced photocatalyst-free conditions

Green Chemistry, Год журнала: 2022, Номер 24(24), С. 9475 - 9481

Опубликована: Янв. 1, 2022

A photocatalyst-free visible-light-promoted remote C(sp 3 )–H heteroarylation of N -fluoroamides with quinoxalin-2(1 H )-ones was developed. All types δ-C(sp bonds in the could be site-specific activated through 1,5-HAT process.

Язык: Английский

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Merging N‐Heterocyclic Carbene Organocatalysis with Hydrogen Atom Transfer Strategy

ChemCatChem, Год журнала: 2022, Номер 15(4)

Опубликована: Ноя. 29, 2022

Abstract Radical N ‐heterocyclic carbene (NHC) organocatalysis has progressed significantly in recent years, enabling various incredible transformations. However, prefunctionalized substrates bearing a redox functionality were always required. As result, the direct functionalization of aliphatic C−H bonds simple remains challenge. This situation was changed once hydrogen transfer atom (HAT) strategy successfully applied radical NHC catalysis very recently. concept paper focused on discussion merging with classical intramolecular 1,5‐HAT process. Moreover, unprecedented application intermolecular HAT is highlighted as novel model showing great synthetic promise.

Язык: Английский

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