Nitroxyl Catalysts for Six-Membered Ring Bromolactonization and Intermolecular Bromoesterification of Alkenes with Carboxylic Acids

Electrophilic halogenation reactions have been a reliable approach to accessing organohalides. During the past decades, various catalytic systems have been developed for the activation of haleniums. However, there is still a short of effective catalysts, which could cover various halogenation reactions and broad scope of unsaturated compounds. Herein, TEMPO (2,2,6,6-tetramethylpiperidine nitroxide) and its derivatives are disclosed as active catalysts for electrophilic halogenation of olefins, alkynes, and aromatics. These catalysts are stable, readily available, and reactive enough to activate haleniums including Br+, I+ and even Cl+ reagents. This catalytic system is applicable to various halogenations including haloarylation of olefins or dibromination of alkynes, which were rarely realized in previous Lewis base catalysis or Lewis acid catalysis. The high catalytic ability is attributed to a synergistic activation model of electrophilic halogenating reagents, where the carbonyl group and the halogen atom are both activated by present TEMPO catalysis.

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“…Based on the above results and previous reports 76,86 , a plausible mechanism of present TEMPO catalysis is proposed (Fig. 9).…”

Section: Resultssupporting

confidence: 77%

“…In this work, TEMPO + and its derivatives, which could be generated in situ from commercially available TEMPO [83][84][85][86] and electrophilic halogenating reagents, were developed as diverse and efficient catalysts in various halogenation reactions. Besides bromonium and iodonium, the chloronium was also strongly activated by catalytic amount of TEMPO + .…”

mentioning

confidence: 99%

Oxoammonium salts are catalysing efficient and selective halogenation of olefins, alkynes and aromatics

Wang

Yang

et al. 2021

Nat Commun

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“…In 2021, Moriyama et al first revealed the Lewis acidity of oxoammonium species using computational evidence. 236 They reported that AZADO catalyzes the bromolactonization of alkenes with NBS. They computationally proposed that an in-situ generated oxoammonium species activated NBS upon coordination to the carbonyl group on the nitrogen center.…”

Section: -8-3 Other Oxidative Transformations (Scheme 38)mentioning

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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“…32b Recently, Matsubara has developed a trans-cyclooctene catalyst 26 for the bromolactonization of olefinic acid 24 to give lactone 25. This method makes use of the sterically protected alkene to facilitate the transfer of an electrophilic bromine from N-bromoacetamide to the alkene substrate via the bromiranium species F. 33 Some other examples of new catalyst/promoter developments for electrophilic bromination reactions include the use of iodobenzene derivative 27, 34 morpholine-HFIP salt, 35 nitroxyl 28, 36 indole 29, 37 and zwitterion 30. 38 The discovery of novel bromine carriers has also played a critical role in the advancement of these bromination reactions.…”

Section: Some New Catalysts and Reagents For Brominationmentioning

confidence: 99%

Recent Advances in C–Br Bond Formation

Wong¹,

Yeung²

2021

Synlett

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Organobromine compounds are extremely useful in organic synthesis. In this perspective, a focused discussion on some recent advancements in C–Br bond-forming reactions is presented.1 Introduction2 Selected Recent Advances2.1 Catalytic Asymmetric Bromopolycyclization of Olefinic Substrates2.2 Catalytic Asymmetric Intermolecular Bromination2.3 Some New Catalysts and Reagents for Bromination2.4 Catalytic Site-Selective Bromination of Aromatic Compounds2.5 sp3 C–H Bromination via Atom Transfer/Cross-Coupling3 Outlook

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Nitroxyl Catalysts for Six-Membered Ring Bromolactonization and Intermolecular Bromoesterification of Alkenes with Carboxylic Acids

Cited by 18 publications

References 70 publications

Oxoammonium salts are catalysing efficient and selective halogenation of olefins, alkynes and aromatics

Oxoammonium salts are catalysing efficient and selective halogenation of olefins, alkynes and aromatics

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

Recent Advances in C–Br Bond Formation

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