7 Electrochemically Generated Nitrogen-Centered Radicals

2022 ◽  
Author(s):  
Z.-W. Hou ◽  
H.-C. Xu
Keyword(s):  
Hydrogen Atom ◽  
Organic Synthesis ◽  
Recent Progress ◽  
Reactive Intermediates ◽  
Hydrogen Atom Abstraction ◽  
Addition Reactions ◽  
Electrochemical Generation ◽  
Nitrogen Containing Compounds

Nitrogen-centered radicals are versatile reactive intermediates for organic synthesis. This chapter describes recent progress in the electrochemical generation and reactions of nitrogen-centered radicals. Under electrochemical conditions, various nitrogen-centered radicals are generated through electrolysis of readily available precursors such as N—H bonds or azides. These reactive intermediates undergo addition reactions to π-systems or hydrogen-atom abstraction to generate various nitrogen-containing compounds.

Recent Advances in Radical-Involved Alkynylation of Unactivated C(sp3)–H Bonds by Hydrogen Atom Abstraction

Synlett ◽  
2020 ◽  
Author(s):  
Zheng-Hua Zhang ◽  
He Wei ◽  
Zhong-Liang Li ◽  
Xin-Yuan Liu
Keyword(s):  
Drug Discovery ◽  
Hydrogen Atom ◽  
Organic Synthesis ◽  
Recent Progress ◽  
Hydrogen Atom Abstraction ◽  
Major Research ◽  
Research Topics ◽  
Reaction Conditions ◽  
Metal Catalyzed ◽  
Intramolecular Hydrogen

AbstractThe direct C(sp3)–H functionalization is one of the major research topics in synthetic chemistry since C(sp3)–H bonds are ubiquitous in every aspect of chemistry. Despite impressive advances in transition-metal-catalyzed C(sp3)–H activation, the radical-initiated process via hydrogen atom abstraction (HAA) of C(sp3)–H bonds represents a more appealing strategy owing to the mild reaction conditions and good regioselectivity. Given the importance of alkynes as versatile synthons in organic synthesis and key structural motifs in drug discovery, great efforts have been made toward their synthesis via the combination of HAA and alkynylation process in recent years. This review summarizes the recent progress in radical-initiated C(sp3)–H alkynylation reactions with emphasis on the alkynylating reagents and mechanistic discussion.1 Introduction2 Alkynylation of C(sp3)–H via Intermolecular Hydrogen Atom Abstraction3 Alkynylation of C(sp3)–H via Intramolecular Hydrogen Atom Abstraction4 Conclusion

1.9 Oxygen-Centered Radicals

2021 ◽  
Author(s):  
J. Zhang ◽  
D. Liu ◽  
Y. Chen
Keyword(s):  
Hydrogen Atom ◽  
Visible Light ◽  
Organic Synthesis ◽  
Reactive Intermediates ◽  
Radical Addition ◽  
Hydrogen Atom Transfer ◽  
Reaction Conditions ◽  
Recent Advances ◽  
Carbon Carbon Bonds ◽  
Induced Reaction

AbstractOxygen-centered radicals (R1O•) are reactive intermediates in organic synthesis, with versatile synthetic utilities in processes such as hydrogen-atom transfer (HAT), β-fragmentation, radical addition to unsaturated carbon–carbon bonds, and rearrangement reactions. In this review, we focus on recent advances in the generation and transformation of oxygen-centered radicals, including (alkyl-, α-oxo-, aryl-) carboxyl, alkoxyl, aminoxyl, phenoxyl, and vinyloxyl radicals, and compare the reactivity of oxygen-centered radicals under traditional reaction conditions with their reactivity under visible-light-induced reaction conditions.

Hydrogen atom abstraction and addition reactions of charged phenyl radicals with aromatic substrates in the gas phase

2001 ◽  
Vol 210-211 ◽  
pp. 511-520 ◽  
Author(s):  
Luis E. Ramı́rez-Arizmendi ◽  
Leo Guler ◽  
Joseph J. Ferra ◽  
Kami K. Thoen ◽  
Hilkka I. Kenttämaa
Keyword(s):  
Hydrogen Atom ◽  
Gas Phase ◽  
Hydrogen Atom Abstraction ◽  
Addition Reactions ◽  
Phenyl Radicals ◽  
Aromatic Substrates

Recent advances in Minisci-type reactions and applications in organic synthesis

2020 ◽  
Vol 24 ◽  
Author(s):  
Wengui Wang ◽  
Shoufeng Wang
Keyword(s):  
Free Radical ◽  
Hydrogen Atom ◽  
Organic Synthesis ◽  
Radical Reactivity ◽  
Atom Loss ◽  
Radical Generation ◽  
In Situ Generation ◽  
Thermal Cleavage ◽  
Synthetic Chemist

Abstract:: Minisci-type reactions have become widely known as reactions that involve the addition of carbon-centered radicals to basic heteroarenes followed by formal hydrogen atom loss. While the originally developed protocols for radical generation remain in active use today, in recent years by a new array of radical generation strategies allow use of a wider variety of radical precursors that often operate under milder and more benign conditions. New transformations based on free radical reactivity are now available to a synthetic chemist looking to utilize a Minisci-type reaction. Radical-generation methods based on photoredox catalysis and electrochemistry, which utilize thermal cleavage or the in situ generation of reactive radical precursors, have become popular approaches. Our review will cover the remarkably literature that has appeared on this topic in recent 5 years, from 2015-01 to 2020-01, in an attempt to provide guidance to the synthetic chemist, on both the challenges that have been overcome and applications in organic synthesis.

O-AcylTEMPOs, a Modified and Fundamental, but Unexplored Carboxylic Derivative: Recent Progress in Synthetic Applications

2019 ◽  
Vol 23 (19) ◽  
pp. 2102-2121
Author(s):  
Hiroyuki Kawafuchi ◽  
Lijian Ma ◽  
Md Imran Hossain ◽  
Tsutomu Inokuchi
Keyword(s):  
Organic Synthesis ◽  
Recent Progress ◽  
Knoevenagel Condensation ◽  
Acid Synthesis ◽  
Amino Acid Synthesis ◽  
Electrophilic Amination ◽  
Weinreb Amides ◽  
Anionic Species ◽  
Diastereoselective Addition ◽  
Carbonyl Function

O-Acylated 2,2,6,6-tetramethylpiperidine-N-oxyls (abbr. O-AcylTEMPOs) are easily available and stable carboxylic derivatives, but their utility in organic synthesis is unexplored in contrast to analogues, such as the N-methoxy-N-methylamides, known as Weinreb amides. Especially, the O–N unit of the O-acylTEMPOs dictates a fairly electronwithdrawing character for the carbonyl function. This enhances the reactivity and stability of the resulting enolate ions. Accordingly, O-acylTEMPOs allow various transformations and this review encompasses seven topics: (1) Reactivity of O-acylTEMPOs towards nucleophiles and chemoselective transformations, (2) Reactivity of anionic species derived from O-acylTEMPOs, (3) E-Selective Knoevenagel condensation of acetoacetylTEMPOs and synthesis of furans, (4) Electrocyclization of 2,4-dienones derived from acetoacetic derivatives and 2-substituted enals, (5) Diastereoselective addition of amide anion to O-(2-alkenoyl)TEMPOs and β-amino acid synthesis, (6) Thermolysis of O-acylTEMPOs, and (7) Applications for Umpolung reactions using O-benzoylTEMPOs, useful for the electrophilic amination of alkenes and alkynes.

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