2367-82-0Relevant articles and documents
Photochemistry of Polyhaloarenes. 6. The Fragmentation of Polyfluoroarene Radical Anions
Freeman, Peter K.,Srinivasa, Ramanujan
, p. 252 - 256 (1987)
The quantum yields for photolyses of pentafluorobenzene in the presence of different concentrations of triethylamine in acetonitrile and pentane were determined at 254 nm.Excimer formation was probed through a study of the quantum yield dependence for pentafluorobenzene photolysis upon substrate concentration in the absence of triethylamine.The linear dependence of 1/Φ vs. 1/(ArF) is complemented by an analysis of product composition, which revealed the production in a 30-min photolysis of the following: 1.2.3.5-tetrafluorobenzene (2) (0.11percent), 1,2,4,5-tetrafluorobenzene (3) (1.09percent), 1,2,3,4-tetrafluorobenzene (4) (0.09percent), octafluorobiphenyl (four isomers, 0.26, 0.85, 0.91, and 0.8percent), and HF (3.01percent).The regiochemistry of the monodefluorination of pentafluorobenzene, 1,2,3,5-tetrafluorobenzene, and 1,2,3,4-tetrafluorobenzene in the presence of triethylamine in acetonitrile or pentane (cyclohexane) was determined and is rationalized in terms of fission of the parent radical anion through a bent transition state.
Stopped-Flow 19F NMR Spectroscopic Analysis of a Protodeboronation Proceeding at the Sub-Second Time-Scale
Wei, Ran,Hall, Andrew M. R.,Behrens, Richard,Pritchard, Mark S.,King, Edward J.,Lloyd-Jones, Guy C.
, p. 2331 - 2342 (2021)
In-situ NMR spectroscopic analysis of homogeneous reactions is an essential tool for mechanistic analysis in organic and organometallic chemistry. However, rapid non-equilibrium reactions, that are initiated by mixing, require specialized approaches. We report herein on a study of the factors that ensure quantitative results in a recently-developed technique for stopped-flow NMR spectroscopy. The influence of some of the key parameters on quantitation is studied by 19F NMR spectroscopic analysis of the kinetics and activation parameters for the base-catalyzed protodeboronation of highly-reactive polyfluorinated arylboronic acids, with half-lives as low as 0.1 seconds. The effects of spin relaxation, pre-magnetization, heat-transfer versus reaction enthalpy, and mixing-efficiency are analyzed in detail. We also compare and contrast choice of pulse angle, interscan delay, and use of pseudo real-time by interleaving, as means to achieve an optimal balance between temporal resolution and sensitivity.
Transition-Metal-Free Catalytic Hydrodefluorination of Polyfluoroarenes by Concerted Nucleophilic Aromatic Substitution with a Hydrosilicate
Kikushima, Kotaro,Grellier, Mary,Ohashi, Masato,Ogoshi, Sensuke
supporting information, p. 16191 - 16196 (2017/11/27)
A transition-metal-free catalytic hydrodefluorination (HDF) reaction of polyfluoroarenes is described. The reaction involves direct hydride transfer from a hydrosilicate as the key intermediate, which is generated from a hydrosilane and a fluoride salt. The eliminated fluoride regenerates the hydrosilicate to complete the catalytic cycle. Dispersion-corrected DFT calculations indicated that the HDF reaction proceeds through a concerted nucleophilic aromatic substitution (CSNAr) process.
Base-Catalyzed Aryl-B(OH)2 Protodeboronation Revisited: From Concerted Proton Transfer to Liberation of a Transient Aryl Anion
Cox, Paul A.,Reid, Marc,Leach, Andrew G.,Campbell, Andrew D.,King, Edward J.,Lloyd-Jones, Guy C.
supporting information, p. 13156 - 13165 (2017/09/26)
Pioneering studies by Kuivila, published more than 50 years ago, suggested ipso protonation of the boronate as the mechanism for base-catalyzed protodeboronation of arylboronic acids. However, the study was limited to UV spectrophotometric analysis under acidic conditions, and the aqueous association constants (Ka) were estimated. By means of NMR, stopped-flow IR, and quenched-flow techniques, the kinetics of base-catalyzed protodeboronation of 30 different arylboronic acids has now been determined at pH > 13 in aqueous dioxane at 70 °C. Included in the study are all 20 isomers of C6HnF(5-n)B(OH)2 with half-lives spanning 9 orders of magnitude: a and Sδ values, kinetic isotope effects (2H, 10B, 13C), linear free-energy relationships, and density functional theory calculations, we have identified a mechanistic regime involving unimolecular heterolysis of the boronate competing with concerted ipso protonation/C-B cleavage. The relative Lewis acidities of arylboronic acids do not correlate with their protodeboronation rates, especially when ortho substituents are present. Notably, 3,5-dinitrophenylboronic acid is orders of magnitude more stable than tetra-and pentafluorophenylboronic acids but has a similar pKa.
Addition of Carbon-Fluorine Bonds to a Mg(I)-Mg(I) Bond: An Equivalent of Grignard Formation in Solution
Bakewell, Clare,White, Andrew J. P.,Crimmin, Mark R.
supporting information, p. 12763 - 12766 (2016/10/14)
Addition of the carbon-fluorine bond of a series of perfluorinated and polyfluorinated arenes across the Mg-Mg bond of a simple coordination complex proceeds rapidly in solution. The reaction results in the formation of a new carbon-magnesium bond and a new fluorine-magnesium bond and is analogous to Grignard formation in homogeneous solution.
Microwave-accelerated fluorodenitrations and nitrodehalogenations: expeditious routes to labeled PET ligands and fluoropharmaceuticals
LaBeaume, Paul,Placzek, Michael,Daniels, Mathew,Kendrick, Ian,Ng, Patrick,McNeel, Melissa,Afroze, Roushan,Alexander, Abigail,Thomas, Rhiannon,Kallmerten, Amy E.,Jones, Graham B.
experimental part, p. 1906 - 1909 (2010/09/07)
Methods for the expeditious fluorination of arenes have been investigated, using readily available fluoride sources. An optimized procedure for microwave-accelerated fluorodenitration has been developed, giving good to excellent yields in less than 10 min, rendering it practical for use in the preparation of F18 labeled ligands for PET imaging. Application of the method in the synthesis of CNS agents is demonstrated, and a practical method for the preparation of substrates is also presented.
Polyfluoroorganoboron-oxygen compounds. 2 [1]: Base-catalysed hydrodeboration of polyfluorophenyl(dihydroxy)boranes
Frohn,Adonin,Bardin,Starichenko
, p. 2834 - 2838 (2008/10/08)
Polyfluorinated phenyl(dihydroxy)boranes C6H5-nFnB(OH)2 (n = 3 - 5) underwent hydrodeboration (formal replacement of the (dihydroxy)boryl group by hydrogen) in the presence of bases (MeOH, 33% H2O-MeO
Preparation process of fluorine substituted aromatic compound
-
, (2008/06/13)
A preparation process of a fluorine substituted aromatic compound comprising reacting an alkali metal or alkali earth metal salt of an aromatic compound having a hydroxy group with an organic fluorinating agent is disclosed. As a representative fluorinating agent, a bis-dialkylamino-difluoromethane compound, for example, 2,2′-difluoro-1,3-dimethylimidazolidine, is exemplified. According to the process, an industrially useful fluorinated aromatic compound, for example, a fluorobenzene, a fluorine substituted benzophenone, a fluorine substituted diarylsulfone can be prepared with ease in economy without specific equipment.
Reactions of polyfluoroaromatic compounds with electrophilic agents in the presence of tris(dialkylamino)phosphine: 6. * Reactions of halogenotetrafluorobenzenes RC6F4X (X = Cl, Br, or I) with chlorotrimethylsilane
Bardin
, p. 780 - 785 (2007/10/03)
The rate of replacement of the halogen atom in isomers of RC6F4X (X = Cl, Br, or I) by the SiMe3 group under the action of Me3SiCl and P(NEt2)3 depends on the nature and the mutual arrangement of the substituents X and R. In addition to silyldehalogenation, compounds C6HF4X (X = Br or I) undergo silyldeprotonation and reduction to tetrafluorobenzenes.
Reaction of polyfluoroaromatic compounds with electrophilic agents in the presence of tris(dialkylamino)phosphines: 7. * Replacement of a halogen by hydrogen in halogenopolyfluoroaromatic compounds
Bardin,Pressman
, p. 786 - 788 (2007/10/03)
A method was developed for the replacement of chlorine, bromine, and iodine in halopolyfluoroaromatic compounds by hydrogen under the action of P(NEt2)3 and a proton donor.