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

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.

2-Deoxyribose Radicals in the Gas Phase and Aqueous Solution. Transient Intermediates of Hydrogen Atom Abstraction from 2-Deoxyribofuranose

2005 ◽  
Vol 70 (11) ◽  
pp. 1769-1786 ◽  
Author(s):  
Luc A. Vannier ◽  
Chunxiang Yao ◽  
František Tureček
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Computational Study ◽  
Hydrogen Atom Abstraction ◽  
Oh Radical ◽  
Free Energies ◽  
Intramolecular Hydrogen ◽  
Solvation Free Energies ◽  
Transient Intermediates

A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3, C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found to be thermodynamically and kinetically more stable than the oxygen-centered ones. The most stable gas-phase radical, 2-deoxyribofuranos-5-yl (5), is produced by H-atom abstraction from C-5 and stabilized by an intramolecular hydrogen bond between the O-5 hydroxy group and O-1. The order of radical stabilities is altered in aqueous solution due to different solvation free energies. These prefer conformers that lack intramolecular hydrogen bonds and expose O-H bonds to the solvent. Carbon-centered deoxyribose radicals can undergo competitive dissociations by loss of H atoms, OH radical, or by ring cleavages that all require threshold dissociation or transition state energies >100 kJ mol-1. This points to largely non-specific dissociations of 2-deoxyribose radicals when produced by exothermic hydrogen atom abstraction from the saccharide molecule. Oxygen-centered 2-deoxyribose radicals show only marginal thermodynamic and kinetic stability and are expected to readily fragment upon formation.

Radiation and Radiationless Processes in 2,3-Pentanedione; Phosphorescence Lifetime in the Gas Phase

1971 ◽  
Vol 49 (7) ◽  
pp. 987-993 ◽  
Author(s):  
A. W. Jackson ◽  
A. J. Yarwood
Keyword(s):  
Hydrogen Atom ◽  
Triplet State ◽  
Gas Phase ◽  
Ground State ◽  
Hydrogen Atom Abstraction ◽  
Intersystem Crossing ◽  
Phosphorescence Lifetime ◽  
Gaseous State ◽  
Methyl Group ◽  
Intramolecular Hydrogen

Fluorescence and phosphorescence are observed when 2,3-pentanedione in the gaseous state is excited at 365, 405, and 436°nm. The phosphorescence lifetime has been investigated as a function of temperature (298 to 363 °K) and concentration of the diketone (0.5 to 90 × 10−4 M). A mechanism that explains the experimental data is proposed. Apart from the radiative process and an intersystem crossing to the ground state, the triplet state 2,3-pentanedione molecules are removed by two other processes. One is a unimolecular reaction with a rate constant of 1 × 1011 exp (−11.0/RT) s−1 (consistent with an intramolecular hydrogen atom abstraction), and the other is an interaction with ground state molecules. The photochemistry of the triplet state of 2,3-pentanedione is compared with that of biacetyl to consider the effect of substitution of a hydrogen atom by the methyl group on the radiationless processes in diketones.

scholarly journals Metal-catalyzed organic reactions by Resonant Acoustic Mixing

2021 ◽  
Author(s):  
Lori Gonnet ◽  
Cameron Lennox ◽  
Jean-Louis Do ◽  
Ivani Malvestiti ◽  
Stefan Koenig ◽  
...  
Keyword(s):  
Ball Milling ◽  
Organic Synthesis ◽  
Mechanochemical Synthesis ◽  
Catalytic Synthesis ◽  
Antidiabetic Drug ◽  
Ring Closing Metathesis ◽  
Reaction Conditions ◽  
Metal Catalyzed ◽  
Resonant Acoustic Mixing ◽  
Model Reactions

We introduce catalytic organic synthesis by Resonant Acoustic Mixing (RAM): a mechanochemical methodology that does not require bulk solvent or milling media. Using as model reactions ruthenium-catalyzed ring-closing metathesis, ene-yne metathesis and copper-catalyzed sulfonamide-isocyanate coupling, we demonstrate RAM-based mechanochemical synthesis that is faster and operationally simpler than conventional ball milling. Moreover, the method can be readily scaled-up, as demonstrated by straightforward catalytic synthesis of the antidiabetic drug Tolbutamide from hundreds of milligrams to at least 10 grams, without any significant changes in reaction conditions.

Recent Advances in Metal-Catalyzed Heterocyclic C-P Bond Formation

2020 ◽  
Vol 17 ◽  
Author(s):  
Feng Xu ◽  
Yu Hui
Keyword(s):  
Organic Synthesis ◽  
Recent Progress ◽  
Bond Activation ◽  
Low Cost ◽  
Bond Formation ◽  
Phosphorus Compounds ◽  
Catalytic Systems ◽  
Phosphorus Containing ◽  
Synthetic Pesticides ◽  
Metal Catalyzed

Abstract:: The Phosphorus-containing heterocycles are an important class of compounds in organic chemistry. Because of their potential application in many fields, especially the synthetic pesticides, medicine and catalyst, the Phosphorus-containing heterocycles have attracted continuous attention by organic synthesis scientists. The development of efficient and low-cost catalytic systems is great interest for construction heterocycles C–P bond. Usually, the Phosphorus-containing heterocycles is prepared via direct carbon–hydrogen (C–H) bond activation or pre-functionalized of heterocycles with carbon–hydrogen （ P-H） bond of phosphorus compounds reaction by metal-catalyzed. This review summarizes recent progress in the heterocycles C-P bond formation reactions by metal-catalyzed, which mainly focusing on the discussion of the reaction mechanism. Aims to provide efficient methods for the future synthesis and application in this field.

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.

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