Radical Cyclization of N-Methacryloyl-2-arylbenzoimidazoles with Nitriles, Ketones, and tert-Butyl Nitrite under Mild Conditions

Jiang, Lilin; Wang, Ling-Tao; Qiu, Hui; Liu, Fa-Liang; Huang, X.; Cao, Tingting; Ge, Guo‐Ping; Liu, Yilin; Wei, Wanzhi

doi:10.1055/a-1890-7743

Cited by 3 publications

(3 citation statements)

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“…Later, other radical acceptors were also tested along these lines (Scheme ). NO 2 radicals were generated from AgNO 2 , − Fe(NO 3 ) and air, tert -butyl nitrite and air, − , or sodium nitrite and potassium persulfate . Nitrogen dioxide readily adds to alkenes, and the resulting adduct C radicals couple efficiently with TEMPO to the corresponding nitroethyl alkoxyamines.…”

Section: Nitroxides In Free-radical Chemistrymentioning

confidence: 99%

“…In these cases, decarboxylation takes place during the reaction. Recently, radical addition of NO 2 to an acrylate with a subsequent homolytic aromatic substitution was presented …”

Section: Nitroxides In Free-radical Chemistrymentioning

confidence: 99%

“…(d) 1,6-Enynes,1320 (e) Alkynoic Acids,1321 (f) Acrylates,1322 and (g) N-Benzimidazolylmethacrylamides1324 …”

mentioning

confidence: 99%

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Organic Synthesis Using Nitroxides

Leifert

Studer

2023

Chem. Rev.

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Nitroxides, also known as nitroxyl radicals, are long-lived or stable radicals with the general structure R 1 R 2 N−O • . The spin distribution over the nitroxide N and O atoms contributes to the thermodynamic stability of these radicals. The presence of bulky N-substituents R 1 and R 2 prevents nitroxide radical dimerization, ensuring their kinetic stability. Despite their reactivity toward various transient C radicals, some nitroxides can be easily stored under air at room temperature. Furthermore, nitroxides can be oxidized to oxoammonium salts (R 1 R 2 N�O + ) or reduced to anions (R 1 R 2 N−O − ), enabling them to act as valuable oxidants or reductants depending on their oxidation state. Therefore, they exhibit interesting reactivity across all three oxidation states. Due to these fascinating properties, nitroxides find extensive applications in diverse fields such as biochemistry, medicinal chemistry, materials science, and organic synthesis. This review focuses on the versatile applications of nitroxides in organic synthesis. For their use in other important fields, we will refer to several review articles. The introductory part provides a brief overview of the history of nitroxide chemistry. Subsequently, the key methods for preparing nitroxides are discussed, followed by an examination of their structural diversity and physical properties. The main portion of this review is dedicated to oxidation reactions, wherein parent nitroxides or their corresponding oxoammonium salts serve as active species. It will be demonstrated that various functional groups (such as alcohols, amines, enolates, and alkanes among others) can be efficiently oxidized. These oxidations can be carried out using nitroxides as catalysts in combination with various stoichiometric terminal oxidants. By reducing nitroxides to their corresponding anions, they become effective reducing reagents with intriguing applications in organic synthesis. Nitroxides possess the ability to selectively react with transient radicals, making them useful for terminating radical cascade reactions by forming alkoxyamines. Depending on their structure, alkoxyamines exhibit weak C−O bonds, allowing for the thermal generation of C radicals through reversible C−O bond cleavage. Such thermally generated C radicals can participate in various radical transformations, as discussed toward the end of this review. Furthermore, the application of this strategy in natural product synthesis will be presented.

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Section: Nitroxides In Free-radical Chemistrymentioning

confidence: 99%

“…In these cases, decarboxylation takes place during the reaction. Recently, radical addition of NO 2 to an acrylate with a subsequent homolytic aromatic substitution was presented …”

Section: Nitroxides In Free-radical Chemistrymentioning

confidence: 99%