C–H functionalization of pyridines

Organic & Biomolecular Chemistry, Год журнала: 2023, Номер 21(28), С. 5671 - 5690

Опубликована: Янв. 1, 2023

This review discusses known approaches for selective pyridine C–H editing, focusing on recent discoveries uniquely suited to pyridines.

Язык: Английский

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Organic Reactions Enabled by Mechanical Force‐Induced Single Electron Transfer

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

Опубликована: Июнь 18, 2024

Mechanochemical reactions, achieved through milling, grinding, or other mechanical actions, have emerged as a solvent-free alternative to traditional solution-based chemistry. Mechanochemistry not only provides the opportunity eliminate bulk solvent use, reducing waste generation, but also unveils new reaction strategy which enables realization of reactions previously inaccessible in solution. While majority organic facilitated by force traditionally follow two-electron transfer pathways similar their counterparts, field mechanochemically induced single-electron (SET) has witnessed rapid development. This review outlines examples mechanochemical SET process, focusing on reagents that initiate SET, thereby positioning mechanochemistry burgeoning within realm

Язык: Английский

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Mechanochemistry‐Amended Barbier Reaction as an Expedient Alternative to Grignard Synthesis**

Angewandte Chemie International Edition, Год журнала: 2023, Номер 62(39)

Опубликована: Июнь 30, 2023

Organomagnesium halides (Grignard reagents) are essential carbanionic building blocks widely used in carbon-carbon and carbon-heteroatom bond-forming reactions with various electrophiles. In the Barbier variant of Grignard synthesis, generation air- moisture-sensitive reagents occurs concurrently their reaction an electrophile. Although operationally simpler, classic approach suffers from low yields due to multiple side reactions, thereby limiting scope its application. Here, we report a mechanochemical adaptation Mg-mediated reaction, which overcomes these limitations facilitates coupling versatile organic (e.g., allylic, vinylic, aromatic, aliphatic) diverse range electrophilic substrates aromatic aldehydes, ketones, esters, amides, O-benzoyl hydroxylamine, chlorosilane, borate ester) assemble C-C, C-N, C-Si, C-B bonds. The has advantage being essentially solvent-free, simple, immune air, surprisingly tolerant water some weak Brønsted acids. Notably, solid ammonium chloride was found improve ketones. Mechanistic studies have clarified role mechanochemistry process, indicating transient organometallics facilitated by improved mass transfer activation surface magnesium metal.

Язык: Английский

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Mechanochemical C−H Arylation and Alkylation of Indoles Using 3 d Transition Metal and Zero‐Valent Magnesium

Chemistry - A European Journal, Год журнала: 2024, Номер 30(26)

Опубликована: Янв. 31, 2024

Although the 3 d transition-metal catalyzed C-H functionalization have been extensively employed to promote formation of valuable carbon-carbon bonds, persistent problems, including use sensitive Grignard reagents and rigorous operations (solvent-drying, inert gas protection, metal pre-activation RMgX addition rate control), still leave great room for further development sustainable methodologies. Herein, we report a mechanochemical technology toward in-situ preparation highly organomagnesium reagents, thus building two general catalytic platforms that enables regioselective arylation alkylation indoles with wide variety halides (including those containing post transformable functionalities heteroaromatic rings). This strategy also brings unique reactivity high step-economy in producing functionalized N-free indole products.

Язык: Английский

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Visible-Light-Mediated Three-Component Alkene 1,2-Alkylpyridylation Reaction Using Alkylboronic Acids as Radical Precursors for the Synthesis of 4-Alkylpyridines

The Journal of Organic Chemistry, Год журнала: 2025, Номер unknown

Опубликована: Март 3, 2025

We report the photocatalyzed three-component alkene 1,2-alkylpyridylation reaction between alkylboronic acids, 4-cyanopyridine, and an olefin to achieve pyridination alkylation of synthesis structurally diversified 4-alkylpyridines. The readily available easily manipulated acids were used as alkyl radical precursors. reactions take place under mild conditions with a broad substrate scope are easy scale up gram level, they therefore potential practical value for structural modification biologically active alkylpyridine derivatives.

Язык: Английский

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Mechanometallaphotoredox Catalysis: Utilizing Increased Throughput Mechanochemistry to Develop Solvent-Minimized Aryl Amination and C(sp2)-C(sp3) Cross-Coupling Reactions with Increased Tolerance to Aerobic Conditions

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Май 22, 2025

Photocatalysis as a tool used in organic synthesis has predominantly relied on the use of solvents, be it under homogeneous or heterogeneous conditions. In particular, metallaphotoredox catalysis reactions commonly toxic solvents such DMA and DMF. Herein, we demonstrate how mechanophotocatalysis, synergistic union mechanochemistry photocatalysis, is compatible with this class dual involving both photocatalyst nickel(II) cocatalysts. Using ball milling, these mechanistically complex can conducted absence bulk solvent air, affording high-yielding aryl aminations C(sp2)-C(sp3) cross-couplings alkyl carboxylic acids, trifluoroborate salts, bromides. These advances are facilitated by introduction novel reaction vessel design for conducting four mechanophotocatalysis simultaneously. This work highlights promise solvent-minimized photocatalysis reactions, demonstrating that examples redundant, thus significantly reducing waste stream. Through time-resolved photoluminescence studies, observed excited states five different photocatalysts were quenched oxygen more solution than solid state, providing evidence origin increased tolerance to aerobic conditions experience.

Язык: Английский

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Mechanochemical Synthesis of Arylsilanes via Barbier‐Type Reaction between Aryl Halides and Chlorosilanes with Magnesium

Advanced Synthesis & Catalysis, Год журнала: 2024, Номер 366(7), С. 1509 - 1516

Опубликована: Фев. 19, 2024

Abstract The reaction of chlorosilanes with organometallic reagents is an old and well‐developed approach to organosilicon compounds, however, its application was limited due the sensitivity air, water. Here we display a mechanochemical access arylsilanes via Barbier‐type aryl halide magnesium. By treatment two halides Mg powder under electromagnetic milling, series are obtained within 15 minutes. Taking advantages this protocol features transition‐metal free, good functional group tolerance, air stable mild conditions.

Язык: Английский

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Purple Light-Promoted Coupling of Bromopyridines with Grignard Reagents via SET

The Journal of Organic Chemistry, Год журнала: 2024, Номер 89(10), С. 7148 - 7155

Опубликована: Май 8, 2024

Alkyl- and arylpyridines 2,2′-bipyridines are conventionally prepared by Minisci reactions of pyridines transition metal-catalyzed coupling halopyridines. Herein, purple light-promoted radical 2- or 4-bromopyridines with Grignard reagents in Et2O a mixture tetrahydrofuran regular glassware without the need for metal catalyst were disclosed first time. Methyl, primary secondary alkyl, cycloalkyl, aryl, heteroaryl, pyridyl, alkynyl compatible protocol. As result, alkyl- easily prepared. Single electron transfer from reagent to bromopyridine was stimulated light. An extruded dimerization worked as catalyst. Light on/off experiments indicated that constant irradiation required product formation. Studies clock substrates verified involvement pyridyl noninvolvement an alkyl aryl reagent. The available proof supports photoinduced SRN mechanism new reactions.

Язык: Английский

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para-Selective radical alkylation of pyridines with diacyl peroxides and peresters

Organic Chemistry Frontiers, Год журнала: 2024, Номер 11(14), С. 3849 - 3854

Опубликована: Янв. 1, 2024

A regioselective para -alkylation of pyridines using alkyl carboxylic acid-derived diacyl peroxides or peresters is reported. This reaction proceeds under mild conditions, and late-stage functionalization complex can be realized.

Язык: Английский

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Stable Meisenheimer Complexes as Powerful Photoreductants Readily Obtained from Aza‐Heteroaromatic Compounds

Angewandte Chemie International Edition, Год журнала: 2024, Номер 63(44)

Опубликована: Июль 30, 2024

Abstract Excited states of radical anions derived from the photoreduction stable organic molecules are suggested to serve as potent reductants. However, excited these species too short‐lived allow bimolecular quenching processes. Recently, singlet state Meisenheimer complexes, which possess a long‐lived state, was identified competent for reduction challenging substrates (−2.63 V vs. SCE, saturated calomel electrode). To produce reasonably and simply accessible different addition n BuLi readily available aromatic heterocycles investigated, photoreactivity generated studied. In this paper, we present straightforward preparation family powerful photoreductants (*E ox < −3 SCE in their states, determined by DFT time‐dependent TD‐DFT calculations; DFT, density functional theory) that can induce dehalogenation electron‐rich aryl chlorides form C−C bond through cyclization. Photophysical analyses computational studies combination with experimental mechanistic investigations demonstrate ability adduct act strong electron donor under visible light irradiation.

Язык: Английский

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