369-18-6Relevant academic research and scientific papers
Thermodynamic study of σH complexes in nucleophilic aromatic substitution reactions: Relative stabilities of electrochemically generated radicals
Gallardo, Iluminada,Guirado, Gonzalo
scheme or table, p. 2463 - 2472 (2009/04/06)
The mechanism for the electrochemical oxidation of σH complexes, such as 1-hydro-1-alkoxy/sulfoxy or -fluoro-2,4-dinitro/2,4,6- trinitrocyclohexadienyl anions, has been widely studied by means of cyclic voltammetry and controlled-potential electrolysis. Previous studies have shown that the electrochemical oxidation of σH complexes, formed by the addition of carbon or nitrogen nucleophiles followed by a two electron mechanism, corresponding to the formal elimination of the hydride anion (nucleophilic aromatic substitution of hydrogen mechanism, the NASH mechanism). For these σH complexes (Nu- = OH-, -OR, -SR, -F), the electrochemical reaction takes place by a one-electron mechanism and is followed by the radical elimination of the leaving group with the consequent recovery of the starting material. This mechanism is similar to that proposed for the electrochemical oxidation of σX complexes (nucleophilic aromatic substitution of a heteroatom, the NASX mechanism). The operating mechanism in each case, the NASH or NASX, can be rationalized in terms of thermodynamics. The standard potentials of the σ complex and/or the leaving group as well as the bond dissociation energies (BDEs) are determinant factors. This study has not led to a significant improvement in the electrochemical preparation of aromatic-substituted compounds, but does help to understand and predict the usefulness or uselessness of using the nucleophilic aromatic substitution route to obtain a desired product. Finally, the current approach extends the electrochemical methodology to different chemical fields, for example, to general nondestructive methods for the detection, identification, and quantification of either organic pollutants or explosives in different solvents. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Elemental fluorine. Part 20. Direct fluorination of deactivated aromatic systems using microreactor techniques
Chambers, Richard D.,Fox, Mark A.,Sandford, Graham,Trmcic, Jelena,Goeta, Andres
, p. 29 - 33 (2008/03/13)
Continuous flow microreactor technology has been used for the direct fluorination of a range of deactivated di- and tri-substituted aromatic systems.
Nucleophilic aromatic substitution for heteroatoms: An oxidative electrochemical approach
Gallardo, Iluminada,Guirado, Gonzalo,Marquet, Jordi
, p. 2548 - 2555 (2007/10/03)
The nucleophilic aromatic substitution for heteroatom through electrochemical oxidation of the intermediate σ-complexes (Meisenheimer complexes) in simple nitroaromatic compounds is reported for the first time (NASX process). The studies have been carried out with hydride, cyanide, fluoride, methoxy, and ethanethiolate anions and n-butylamine as a nucleophile, at the cyclic voltammetry (CV) and preparative electrolysis level. The cyclic voltammetry experiments allow for detection and characterization of the σ-complexes and they have led us to a proposal for the mechanism of the oxidation step. Furthermore, the power of the CV technique in the analysis of the reaction mixture throughout the whole chemical and electrochemical process is described.
Synthesis of Aromatic Fluoro Compounds by Nucleophilic Exchange of Nitro Groups by Fluoride
Effenberger, Franz,Streicher, Willi
, p. 157 - 162 (2007/10/02)
The synthesis of aromatic fluoro compounds from the respective nitro compounds by nucleophilic substitution of nitrite by fluoride is described.Reasonable yields in case of nonactivated nitro compounds are only obtained if the nitrite formed in the reaction is eliminated by acylation. 1-Fluoro-3-nitrobenzene (2) was obtained from 1,3-dinitrobenzene (1), and 1-fluoro-3,5-dinitrobenzene (9) as well as 1,3-difluoro-5-nitrobenzene (10) from 1,3,5-trinitrobenzene (8) in yields up to 92percent by reaction of nitro compounds with potassium fluoride in sulfolane at 180-200 deg C in the presence of phthaloyl dichloride (6); 1,2-difluoro-4-nitrobenzene (12) was formed in 58percent yield from 2,4-dinitro-1-fluorobenzene (11) in the presence of pyromellitoyl tetrachloride (13).
