Redox‐Neutral TEMPO Catalysis: Direct Radical (Hetero)Aryl C−H Di‐ and Trifluoromethoxylation

Lee, Johnny W.; Lim, Sanghyun; Maienshein, Daniel N.; Liu, Peng; Ngai, Ming‐Yu

doi:10.1002/anie.202009490

Cited by 39 publications

(13 citation statements)

References 118 publications

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“…Initially, ( n -Bu 4 N + ) 2 S 2 O 8 2– suffers an homolytic cleavage to afford two equivalents of the oxygen-centered radical • SO 4 – ( n -Bu 4 N + ). These radicals subsequently participate in two process: (a) the generation of species I via the SET process from adduct 19 and (b) the oxidation of TEMPO 21 to species A [TEMPO + ]SO 4 2– ( n -Bu 4 N + ) . After intramolecular 5- endo -trig radical cyclization onto the N -benzoyl moiety, transient cyclohexanedienyl radical species II is oxidized to cation III by the effect of the strong oxidant oxoammonium salt A .…”

Section: Results and Discussionmentioning

confidence: 99%

Synthesis of Polysubstituted Isoindolinones via Radical Cyclization of 1,3-Dicarbonyl Ugi-4CR Adducts Using Tetrabutylammonium Persulfate and TEMPO

et al. 2020

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The development of an efficient method for the synthesis of polysubstituted isoindolinones from 1,3-dicarbonyl Ugi-4CR adducts, employing an aromatic radical cyclization process promoted by tetrabutylammonium persulfate and 2,2,6,6-tetramethyl-1-piperidine 1-oxyl (TEMPO), is described. The protocol allowed the construction of a library of isoindolinones bearing a congested carbon in good to excellent yields under mild conditions and in short reaction times.

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Section: Results and Discussionmentioning

confidence: 99%

Synthesis of Polysubstituted Isoindolinones via Radical Cyclization of 1,3-Dicarbonyl Ugi-4CR Adducts Using Tetrabutylammonium Persulfate and TEMPO

et al. 2020

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“…Having developed a set of efficient photocatalytic conditions, we next sought to investigate alternative approaches for activating BTMP, which do not require light irradiation. While initial results had identified metal salts such as CuCl as suitable stoichiometric activators, we were drawn to the recent report from Ngai and co‐workers using catalytic amounts of (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) as a single electron shuttle with reagent C [6c] . TEMPO is significantly less expensive than [Ru(bpy) 3 ][PF 6 ] 2 while the avoidance of light irradiation brings practical advantages for potential large scale applications [12] .…”

Section: Methodsmentioning

confidence: 99%

Radical C−H Trifluoromethoxylation of (Hetero)arenes with Bis(trifluoromethyl)peroxide

Dix

Golz

Schmid

et al. 2021

Chemistry A European J

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Trifluoromethoxylated (hetero)arenes are of great interest for several disciplines, especially in agro‐ and medicinal chemistry. Radical C−H trifluoromethoxylation of (hetero)arenes represents an attractive approach to prepare such compounds, but the high cost and low atom economy of existing .OCF3 radical sources make them unsuitable for the large‐scale synthesis of trifluoromethoxylated building blocks. Herein, we introduce bis(trifluoromethyl)peroxide (BTMP, CF3OOCF3) as a practical and efficient trifluoromethoxylating reagent that is easily accessible from inexpensive bulk chemicals. Using either visible light photoredox or TEMPO catalysis, trifluoromethoxylated arenes could be prepared in good yields under mild conditions directly from unactivated aromatics. Moreover, TEMPO catalysis allowed for the one‐step synthesis of valuable pyridine derivatives, which have been previously prepared via multi‐step approaches.

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“…226 In 2020, Liu and Ngai et al reported the TEMPO-catalyzed redox-neutral C-H di-and trifluoromethoxylation of (hetero)arenes. 227 The principle of the reaction was similar to the NFSI-mediated amination reaction.…”

Section: -7-1 Oxidation Of Organosulfur Compoundsmentioning

confidence: 99%

The Utility of Oxoammonium Species in Organic Synthesis: Beyond Alcohol Oxidation

Iwabuchi¹,

Nagasawa²

2022

HETEROCYCLES

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Oxoammonium species are electrophilic chemical species generated via single electron oxidation of nitroxyl radicals. Although this species and its salts are known as useful oxidants and active species for (catalytic) oxidation of alcohols into carbonyl compounds in organic synthesis, the benefits of oxoammonium species for the oxidative transformations of numerous types of substrates apart from alcohols has been reported. This review summarizes the synthetic utility of oxoammonium species under both stoichiometric and catalytic conditions with the exception of alcohol oxidation. CONTENTS 1. Introduction 2. Oxoammonium species 3. Oxoammonium species (salt)-mediated oxidative transformation 3-1. Oxidative esterification/amidation 3-2. Oxidation of amines (imines) 3-3. Oxidation of ethers 3-4. Oxidation of enols: α-Aminooxygenation of carbonyl compounds and further applications 3-5. Oxidation of alkenes 3-6. Oxidation of aromatic compounds 3-7. Oxidation of other substrates 3-8. Oxoammonium species for single electron oxidation 3-9. Oxoammonium species as a Lewis acids Conclusions and outlookThis paper is dedicated to Prof. Somsak Ruchirawat on the occasion of his 80th birthday.

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Redox‐Neutral TEMPO Catalysis: Direct Radical (Hetero)Aryl C−H Di‐ and Trifluoromethoxylation

Cited by 39 publications

References 118 publications

Synthesis of Polysubstituted Isoindolinones via Radical Cyclization of 1,3-Dicarbonyl Ugi-4CR Adducts Using Tetrabutylammonium Persulfate and TEMPO

Synthesis of Polysubstituted Isoindolinones via Radical Cyclization of 1,3-Dicarbonyl Ugi-4CR Adducts Using Tetrabutylammonium Persulfate and TEMPO

Radical C−H Trifluoromethoxylation of (Hetero)arenes with Bis(trifluoromethyl)peroxide

The Utility of Oxoammonium Species in Organic Synthesis: Beyond Alcohol Oxidation

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