Cooperative NHC and Photoredox Catalysis for the Synthesis of β‐Trifluoromethylated Alkyl Aryl Ketones

Angewandte Chemie International Edition, Год журнала: 2020, Номер 59(45), С. 19956 - 19960

Опубликована: Июль 23, 2020

Despite the great potential of radical chemistry in organic synthesis, N-heterocyclic carbene (NHC)-catalyzed reactions involving intermediates are not well explored. This communication reports three-component coupling aroyl fluorides, styrenes and Langlois reagent (CF3 SO2 Na) to give various β-trifluoromethylated alkyl aryl ketones with good functional group tolerance moderate high yields by cooperative photoredox/NHC catalysis. The alkene acyltrifluoromethylation proceeds via radical/radical cross ketyl radicals benzylic C-radicals. generated SET reduction situ formed acylazolium ions whereas derive from trifluoromethyl addition onto styrenes.

Язык: Английский

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Photosensitized Intermolecular Carboimination of Alkenes through the Persistent Radical Effect

Angewandte Chemie International Edition, Год журнала: 2019, Номер 59(8), С. 3172 - 3177

Опубликована: Дек. 3, 2019

Abstract An intermolecular, two‐component vicinal carboimination of alkenes has been accomplished by energy transfer catalysis. Oxime esters alkyl carboxylic acids were used as bifunctional reagents to generate both and iminyl radicals. Subsequently, addition the radical an alkene generates a transient for selective radical–radical cross‐coupling with persistent radical. Furthermore, this process provides direct access aliphatic primary amines α‐amino simple hydrolysis.

Язык: Английский

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Cooperative NHC/Photoredox Catalyzed Ring‐Opening of Aryl Cyclopropanes to 1‐Aroyloxylated‐3‐Acylated Alkanes

Angewandte Chemie International Edition, Год журнала: 2021, Номер 60(48), С. 25252 - 25257

Опубликована: Сен. 28, 2021

Cyclopropanes are an important class of building blocks in organic synthesis. Herein, a ring-opening/arylcarboxylation/acylation cascade reaction for the 1,3-difunctionalization aryl cyclopropanes enabled by cooperative NHC and organophotoredox catalysis is reported. The works on monosubstituted that contrast to heavily investigated donor-acceptor more challenging be difunctionalized. key step radical/radical cross coupling benzylic radical generated photoredox cycle with ketyl from cycle. transformation features metal-free conditions tolerates diverse range functionalities.

Язык: Английский

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New Radical Borylation Pathways for Organoboron Synthesis Enabled by Photoredox Catalysis

Angewandte Chemie International Edition, Год журнала: 2020, Номер 59(31), С. 12876 - 12884

Опубликована: Март 31, 2020

Radical borylation using N-heterocyclic carbene (NHC)-BH3 complexes as boryl radical precursors has emerged an important synthetic tool for organoboron assembly. However, the majority of reported methods are limited to reaction modes involving carbo- and/or hydroboration specific alkenes and alkynes. Moreover, generation NHC-boryl radicals relies principally on hydrogen atom abstraction with aid initiators. A distinct method is reported, well pathways enabled by photoredox catalysis. generated via a single-electron oxidation subsequently undergo cross-coupling in-situ-generated anions yield gem-difluoroallylboronates. photoredox-catalyzed arylboration was achieved cyanoarenes arylating components from which elaborated organoborons were accessed. Mechanistic studies verified oxidative formation through single-electron-transfer pathway.

Язык: Английский

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Light‐Driven Carbene Catalysis for the Synthesis of Aliphatic and α‐Amino Ketones

Angewandte Chemie International Edition, Год журнала: 2021, Номер 60(33), С. 17925 - 17931

Опубликована: Июнь 7, 2021

Single-electron N-heterocyclic carbene (NHC) catalysis has gained attention recently for the synthesis of C-C bonds. Guided by density functional theory and mechanistic analyses, we report light-driven aliphatic α-amino ketones using single-electron NHC operators. Computational experimental results reveal that reactivity key radical intermediate is substrate-dependent can be modulated through steric electronic parameters NHC. Catalyst potential harnessed in visible-light driven generation an acyl azolium species undergoes selective coupling with various partners to afford diverse ketone products. This methodology showcased direct late-stage functionalization amino acids pharmaceutical compounds, highlighting utility

Язык: Английский

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Photoenzymatic Hydrogenation of Heteroaromatic Olefins Using ‘Ene’‐Reductases with Photoredox Catalysts

Angewandte Chemie International Edition, Год журнала: 2020, Номер 59(26), С. 10484 - 10488

Опубликована: Март 17, 2020

Flavin-dependent 'ene'-reductases (EREDs) are highly selective catalysts for the asymmetric reduction of activated alkenes. This function is, however, limited to enones, enoates, and nitroalkenes using native hydride transfer mechanism. Here we demonstrate that EREDs can reduce vinyl pyridines when irradiated with visible light in presence a photoredox catalyst. Experimental evidence suggests reaction proceeds via radical mechanism where pyridine is reduced corresponding neutral benzylic solution. DFT calculations reveal this be "dynamically stable", suggesting it sufficiently long-lived diffuse into enzyme active site stereoselective hydrogen atom transfer. distinct from one, highlighting opportunity expand synthetic capabilities existing platforms by exploiting new mechanistic models.

Язык: Английский

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A Photochemical Organocatalytic Strategy for the α‐Alkylation of Ketones by using Radicals

Angewandte Chemie International Edition, Год журнала: 2020, Номер 59(24), С. 9485 - 9490

Опубликована: Фев. 13, 2020

Abstract Reported herein is a visible‐light‐mediated radical approach to the α‐alkylation of ketones. This method exploits ability nucleophilic organocatalyst generate radicals upon S N 2‐based activation alkyl halides and blue light irradiation. The resulting open‐shell intermediates are then intercepted by weakly silyl enol ethers, which would be unable directly attack through traditional two‐electron path. mild reaction conditions allowed functionalization α position ketones with functional groups that not compatible classical anionic strategies. In addition, redox‐neutral nature this process makes it cinchona‐based primary amine catalyst, was used develop rare example enantioselective organocatalytic

Язык: Английский

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Frustrated Radical Pairs: Insights from EPR Spectroscopy

Angewandte Chemie International Edition, Год журнала: 2020, Номер 60(1), С. 53 - 65

Опубликована: Сен. 18, 2020

Abstract Progress in frustrated Lewis pair (FLP) chemistry has revealed the importance of main group elements catalysis, opening new avenues synthetic chemistry. Recently, reactivities pairs have been uncovered that disclose certain combinations acids and bases undergo single‐electron transfer (SET) processes. Here an electron can be transferred from basic donor to a acidic acceptor generate reactive radical (FRP). This minireview aims showcase recent advancements this emerging field covering synthesis pairs, with extensive highlights results Electron Paramagnetic Resonance (EPR) spectroscopy explain nature stability different species observed.

Язык: Английский

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Photocatalytic Anti‐Markovnikov Radical Hydro‐ and Aminooxygenation of Unactivated Alkenes Tuned by Ketoxime Carbonates

Angewandte Chemie International Edition, Год журнала: 2021, Номер 60(40), С. 21997 - 22003

Опубликована: Июль 13, 2021

Abstract A tunable photocatalytic method is reported for anti ‐Markovnikov hydro‐ and aminooxygenation of unactivated alkenes using readily accessible ketoxime carbonates as the diverse functionalization reagents. Mechanistic studies reveal that this reaction initiated through an energy‐transfer‐promoted N−O bond homolysis leading to alkoxylcarbonyloxyl iminyl radicals under visible‐light photocatalysis, followed by addition radical alkenes. By taking advantage different stability radicals, generated carbon either abstracts a hydrogen atom from media form hydrooxygenation product, or it trapped persistent furnish product. Notably, first example direct olefins with regioselectivity involving oxygen‐centered radical.

Язык: Английский

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Regioselective Access to Vicinal Diamines by Metal‐Free Photosensitized Amidylimination of Alkenes with Oxime Esters

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

Опубликована: Сен. 9, 2022

A metal-free photosensitized protocol for regioselective diamination of alkene feedstocks over a single step was developed based on the rationally designed bifunctional reagent, thus affording range differentially protected 1,2-diamines in moderate to high yields. Mechanistic studies reveal that reaction is initiated with triplet-triplet energy transfer between thioxanthone catalyst and followed by fragmentation simultaneously generate long-lived iminyl radical transient amidyl radical. The excellent regioselectivity presumably stems from large reactivity difference two different N-centered species. This characterized regioselectivity, broad functional group tolerance, mild conditions, which would enrich diversity versatility facilitate diversity-oriented synthesis 1,2-diamine-containing complex molecule scaffolds.

Язык: Английский

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