Anion-radical mechanism of bromine exchange by iodine in furan derivatives

1976 ◽  
Vol 12 (12) ◽  
pp. 1317-1322
Author(s):  
V. N. Novikov
Keyword(s):  
Anion Radical ◽  
Radical Mechanism ◽  
Furan Derivatives

The course of reaction of 4-nitrobenzyl bromide and 5-nitrofurfuryl bromide with bases: Operation of anion-radical mechanism

1982 ◽  
Vol 47 (5) ◽  
pp. 1334-1338 ◽  
Author(s):  
Josef Prousek
Keyword(s):  
Electron Transfer ◽  
Reaction Mechanism ◽  
Anion Radical ◽  
Radical Mechanism ◽  
Charge Transfer Complexes ◽  
Chain Reaction ◽  
Electron Transfer Chain ◽  
Initial Stage ◽  
Transfer Chain ◽  
Ethylene Derivative

4-Nitrobenzyl bromide (I) - contrary to 5-nitrofurfuryl bromide (V) - does not react with hard bases in an electron-transfer chain reaction, giving instead product of SN2 reaction. However, its reaction with soft bases affords 1,2-bis(4-nitrophenyl)ethane (III) as anion-radical mechanism product. 5-Nitrofurfuryl bromide reacts with hard bases to give 1,2-bis(5-nitro-2-furyl)ethylene (VI) whereas with soft bases 1,2-bis(5-nitro-2-furyl)ethane (VII) is formed. The derivative VII on reaction with ethanolic NaOH reacts by α-E1cB mechanism under formation of the ethylene derivative VI. The derivative III does not react by this mechanism. The solvent and base effects on the formation of charge-transfer complexes in the initial stage of these reactions in relation to the reaction mechanism are discussed.

Reaction of 2-butenolide and 4-bromo-2-butenolide with 5-aryl-2-furaldehydes and thiolates

1986 ◽  
Vol 51 (10) ◽  
pp. 2181-2185 ◽  
Author(s):  
Tatyana Ya. Kaklyugina ◽  
Larisa A. Badovskaya ◽  
Ludmila N. Sorotskaya ◽  
Nadezhda D. Kozhina ◽  
Adolf Jurášek ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Anion Radical ◽  
Radical Mechanism ◽  
Sodium Salts ◽  
H Nmr

Condensation of 2-butenolide with 5-(4-X-phenyl)-2-furaldehydes (X = H, CH3, OCH3, Br, Cl, NO2) in methanol in the presence of piperidine as catalyst afforded the corresponding 4-[5-(4-X-phenyl-2-furfurylidene)]-2-butenolides. As shown by 1H NMR spectra, the reaction afforded mixtures of Z- and E-isomers which on crystallization were isomerized to the stable Z-isomers (except when X = NO2). 4-Bromo-2-butenolide reacted with sodium salts of 2-mercaptobenzoxazole and 2-mercaptobenzimidazole to give the corresponding 4-(benzazoyl-2-thio)-2-butenolides, probably by an anion-radical mechanism. With arene thiolates, no substitution of the bromo atom took place and the reaction afforded only the corresponding disulfides. The IR and 1H NMR spectra of the synthesized compounds are discussed.

Hydrostibination of Alkynes: A Radical Mechanism

2020 ◽  
Author(s):  
Josh MacMillan ◽  
Katherine Marczenko ◽  
Erin Johnson ◽  
Saurabh Chitnis
Keyword(s):  
Density Functional ◽  
Activation Barrier ◽  
Closed Shell ◽  
Reaction Rates ◽  
Radical Mechanism ◽  
Neutral Radical ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Ionic Mechanisms ◽  
Terminal Acetylenes

The addition of Sb-H bonds to alkynes was reported recently as a new hydroelementation reaction that exclusively yields anti-Markovnikov <i>Z</i>-olefins from terminal acetylenes. We examine four possible mechanisms that are consistent with the observed stereochemical and regiochemical outcomes. A comprehensive analysis of solvent, substituent, isotope, additive, and temperature effects on hydrostibination reaction rates definitively refutes three ionic mechanisms involving closed-shell charged intermediates. Instead the data support a fourth pathway featuring neutral radical Sb<sup>II</sup> and Sb<sup>III</sup> intermediates. Density Functional Theory (DFT) calculations are consistent this model, predicting an activation barrier that is within 1 kcal mol<sup>-1</sup> of the experimental value (Eyring analysis) and a rate limiting step that is congruent with experimental kinetic isotope effect. We therefore conclude that hydrostibination of arylacetylenes is initiated by the generation of stibinyl radicals, which then participate in a cycle featuring Sb<sup>II</sup> and Sb<sup>III</sup> intermediates to yield the observed <i>Z</i>-olefins as products. This mechanistic understanding will enable rational evolution of hydrostibination as a methodology for accessing challenging products such as <i>E</i>-olefins.

Regioselective C3-H Trifluoromethylation of 2H-Indazole Under Transition-Metal-Free Photoredox Catalysis

2019 ◽  
Author(s):  
Arumugavel Murugan ◽  
Venkata Nagarjuna Babu ◽  
Nagaraj Sabarinathan ◽  
Sharada Duddu. S
Keyword(s):  
Transition Metal ◽  
Visible Light ◽  
Practical Approach ◽  
Hypervalent Iodine ◽  
Radical Mechanism ◽  
Photoredox Catalysis ◽  
Metal Free

Here we report a visible-light-promoted metal-free regioselective C3-H trifluoromehtylation reaction that proceeds via radical mechanism and which supported by control experiments. The combination of photoredox catalysis and hypervalent iodine reagent provides a practical approach for the present trifluoromethylation reaction and synthesis of a library of trifluoromethylated indazoles.

Superoxide Anion Radical: Generation and Detection in Cellular and Non-Cellular Systems

2015 ◽  
Vol 22 (37) ◽  
pp. 4234-4256 ◽  
Author(s):  
Renan Chiste ◽  
Marisa Freitas ◽  
Adriana Mercadante ◽  
Eduarda Fernandes
Keyword(s):  
Superoxide Anion ◽  
Anion Radical ◽  
Cellular Systems ◽  
Superoxide Anion Radical ◽  
Radical Generation

Electrochemical reduction of para-substituted 2-acyl-5-phenylfuranes in dimethylformamide

1981 ◽  
Vol 46 (2) ◽  
pp. 498-502 ◽  
Author(s):  
Jozef Černák ◽  
František Tomanovič ◽  
Andrej Staško ◽  
Anna Fedosyevna Oleinikova ◽  
Jaroslav Kováč
Keyword(s):  
Electrochemical Reduction ◽  
Unpaired Electron ◽  
Anion Radical ◽  
Electron Wave ◽  
Epr Method ◽  
Electron Center ◽  
Nitrogen Nucleus ◽  
Nitro Derivatives ◽  
Stable Anion ◽  
Derivatives Of

para Substituted chloro, bromo, and nitro derivatives of 2-acyl-5-phenylfurane are reduced polarographically in a one-electron wave to the corresponding anion radicals, which were studied by the EPR method. The reduction of nitro derivatives, studied by the Kalousek switch, is reversible and leads to a stable anion radical with an unpaired electron center on the nitrogen nucleus; the reduction of the halogen derivatives is only partly reversible and leads to unstable ketyl radicals. The bromo derivatives give polarographic maxima typical for concurrent reactions.

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