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

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 1875 - 1924

Published: Aug. 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.

Language: Английский

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Alkyl Carbon–Carbon Bond Formation by Nickel/Photoredox Cross‐Coupling

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 58(19), P. 6152 - 6163

Published: Oct. 6, 2018

The union of photoredox and nickel catalysis has resulted in a renaissance radical chemistry as well the use nickel-catalyzed transformations, specifically for carbon-carbon bond formation. Collectively, these advances address longstanding challenge late-stage cross-coupling functionalized alkyl fragments. Empowered by notion that photocatalytically generated radicals readily undergo capture Ni complexes, wholly new feedstocks have been realized. Herein, we highlight recent developments several types cross-couplings are accessible exclusively through this approach.

Language: Английский

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Aminoalkyl radicals as halogen-atom transfer agents for activation of alkyl and aryl halides

Science, Journal Year: 2020, Volume and Issue: 367(6481), P. 1021 - 1026

Published: Feb. 27, 2020

Organic halides are important building blocks in synthesis, but their use (photo)redox chemistry is limited by low reduction potentials. Halogen-atom transfer remains the most reliable approach to exploit these substrates radical processes despite its requirement for hazardous reagents and initiators such as tributyltin hydride. In this study, we demonstrate that α-aminoalkyl radicals, easily accessible from simple amines, promote homolytic activation of carbon-halogen bonds with a reactivity profile mirroring classical tin radicals. This strategy conveniently engages alkyl aryl wide range redox transformations construct sp3-sp3, sp3-sp2, sp2-sp2 carbon-carbon under mild conditions high chemoselectivity.

Language: Английский

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Applications of Halogen-Atom Transfer (XAT) for the Generation of Carbon Radicals in Synthetic Photochemistry and Photocatalysis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2292 - 2352

Published: Dec. 9, 2021

The halogen-atom transfer (XAT) is one of the most important and applied processes for generation carbon radicals in synthetic chemistry. In this review, we summarize highlight aspects associated with XAT impact it has had on photochemistry photocatalysis. organization material starts analysis mechanistic then follows a subdivision based nature reagents used halogen abstraction. This review aims to provide general overview fundamental concepts main agents involved objective offering tool understand facilitate development new radical strategies.

Language: Английский

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Generation of Alkyl Radicals: From the Tyranny of Tin to the Photon Democracy

Chemical Reviews, Journal Year: 2020, Volume and Issue: 120(17), P. 9790 - 9833

Published: Aug. 6, 2020

Alkyl radicals are key intermediates in organic synthesis. Their classic generation from alkyl halides has a severe drawback due to the employment of toxic tin hydrides point that "flight tyranny tin" radical processes was considered for long time an unavoidable issue. This review summarizes main alternative approaches unstabilized radicals, using photons as traceless promoters. The recent development photochemical and photocatalyzed enabled discovery plethora new precursors, opening world chemistry broader community, thus allowing era photon democracy.

Language: Английский

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Photons or Electrons? A Critical Comparison of Electrochemistry and Photoredox Catalysis for Organic Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2487 - 2649

Published: Nov. 9, 2021

Redox processes are at the heart of synthetic methods that rely on either electrochemistry or photoredox catalysis, but how do and catalysis compare? Both approaches provide access to high energy intermediates (e.g., radicals) enable bond formations not constrained by rules ionic 2 electron (e) mechanisms. Instead, they 1e mechanisms capable bypassing electronic steric limitations protecting group requirements, thus enabling chemists disconnect molecules in new different ways. However, while providing similar intermediates, differ several physical chemistry principles. Understanding those differences can be key designing transformations forging disconnections. This review aims highlight these similarities between comparing their underlying principles describing impact electrochemical photochemical methods.

Language: Английский

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Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2017 - 2291

Published: Nov. 23, 2021

We present here a review of the photochemical and electrochemical applications multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms which both an proton exchanged together, often concerted elementary step. As such, MS-PCET can function as non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from wide variety common functional groups. introduction practitioner’s guide reaction design, with emphasis on unique energetic selectivity features that characteristic this class. then chapters oxidative N–H, O–H, S–H, C–H homolysis methods, generation corresponding neutral species. Then, reductive PCET activations involving carbonyl, imine, other X═Y π-systems, heteroarenes, where ketyl, α-amino, heteroarene-derived radicals be generated. Finally, we asymmetric catalysis materials device applications. Within each chapter, subdivide by group undergoing homolysis, thereafter type transformation being promoted. Methods published prior end December 2020 presented.

Language: Английский

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Synthetic Photoelectrochemistry

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 59(29), P. 11732 - 11747

Published: Dec. 5, 2019

Photoredox catalysis (PRC) and synthetic organic electrochemistry (SOE) are often considered competing technologies in synthesis. Their fusion has been largely overlooked. We review state-of-the-art photoelectrochemistry, grouping examples into three categories: 1) electrochemically mediated photoredox (e-PRC), 2) decoupled photoelectrochemistry (dPEC), 3) interfacial (iPEC). Such synergies prove beneficial not only for "greenness" chemical selectivity, but also the accumulation of energy accessing super-oxidizing or -reducing single electron transfer (SET) agents. Opportunities challenges this emerging exciting field discussed.

Language: Английский

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Strategic Use of Visible-Light Photoredox Catalysis in Natural Product Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 1717 - 1751

Published: July 7, 2021

Recent progress in the development of photocatalytic reactions promoted by visible light is leading to a renaissance use photochemistry construction structurally elaborate organic molecules. Because rich functionality found natural products, studies product total synthesis provide useful insights into functional group compatibility these new methods as well their impact on synthetic strategy. In this review, we examine syntheses published through end 2020 that employ visible-light photoredox catalytic step. To assist someone interested employing steps discussed, review organized largely nature bond formed

Language: Английский

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Photoredox Generation of Carbon-Centered Radicals Enables the Construction of 1,1-Difluoroalkene Carbonyl Mimics

Angewandte Chemie International Edition, Journal Year: 2017, Volume and Issue: 56(47), P. 15073 - 15077

Published: Sept. 28, 2017

Abstract Described is a facile, scalable route to access functional‐group‐rich gem ‐difluoroalkenes. Using visible‐light‐activated catalysts in conjunction with an arsenal of carbon‐radical precursors, array trifluoromethyl‐substituted alkenes undergoes radical defluorinative alkylation. Nonstabilized primary, secondary, and tertiary radicals can be used install functional groups convergent manner, which would otherwise challenging by two‐electron pathways. The process readily extends other perfluoroalkyl‐substituted alkenes. In addition, we report the development organotrifluoroborate reagent expedite synthesis requisite alkene starting materials.

Language: Английский

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