- Selective Aryl-Fluoride Reductive Elimination from a Platinum(IV) Complex
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A difluoro(mesityl)platinum(IV) complex underwent highly selective reductive elimination of 2-fluoromesitylene upon heating in toluene. Kinetic analysis and DFT calculations suggest that the C-F coupling involves a five-coordinate PtIV transient intermediate resulting from the rate-limiting dissociation of the pyridine ligand.
- Dubinsky-Davidchik, Ina,Goldberg, Israel,Vigalok, Arkadi,Vedernikov, Andrei N.
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Read Online
- Unsymmetrical diaryliodonium phenyltrifluoroborate salts: Synthesis, structure and fluorination
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The unprecedented reaction of organotrifluoroborates salts of unsymmetrical diaryliodoniums to give aryl fluorides is presented. This preliminary report describes the first synthesis of unsymmetrical diaryliodonium phenyltrifluoroborates along with an exe
- Sadek, Omar,Perrin, David M.,Gras, Emmanuel
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Read Online
- Dediazoniation of Arenediazonium Ions. Part XIX. Effect of Thiocyanate Ion in the Reactions of 2,4,6-Trimethylbenzenediazonium Tetrafluoroborate in 2,2,2-trifluoroethanol
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The dediazoniation of 2,4,6-trimethylbenzenediazonium tetrafluoroborate (1) in 2,2,2-trifluoroethanol (TFE) was studied in the presence of potassium thiocyanate.The effect of added salt on the dediazoniation rate, the Nα-Nβ rearrangement (Eqn. 2), the exchange of the 15N-labelled diazo group with molecular nitrogen (Eqn. 3), and the reaction products was determinated.With 0.3M KSCN a dediazoniation-rate increase of 16.5percent was achieved, and the amounts of rearranged and exchanged product were reduced to 88percent and 70percent, respectively, of the values found in pure TFE.The dediazoniation products formed are ArF (3), ArOCH2CF3 (4), ArSCN (5), ArNCS (6) and traces of 5,7-dimethylindazole (7).All the data are in agreement with, and support the previously proposed mechanism (Eqn. 1) of heterolytic dediazoniation of arenediazonium salts.
- Szele, Ivanka,Zollinger, Heinrich,Deshpande, Ashok D.
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Read Online
- Strategy for Selective Csp2-F and Csp2-Csp2Formations from Organoplatinum Complexes
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By changing the parameters of fluorination reaction of bisaryl-platinum(II) complexes, each possible competitive pathway of Ar-Ar and Ar-F formation can be selectively controlled. It was discovered that steric hindrance, type of fluorinating reagent, and
- Sarkissian, Elin,Golbon Haghighi, Mohsen
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supporting information
p. 1016 - 1020
(2021/02/05)
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- Photoredox catalysis with aryl sulfonium salts enables site-selective late-stage fluorination
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Photoredox catalysis, especially in combination with transition metal catalysis, can produce redox states of transition metal catalysts to facilitate challenging bond formations that are not readily accessible in conventional redox catalysis. For arene functionalization, metallophotoredox catalysis has successfully made use of the same leaving groups as those valuable in conventional cross-coupling catalysis, such as bromide. Yet the redox potentials of common photoredox catalysts are not sufficient to reduce most aryl bromides, so synthetically useful aryl radicals are often not directly available. Therefore, the development of a distinct leaving group more appropriately matched in redox potential could enable new reactivity manifolds for metallophotoredox catalysis, especially if arylcopper(iii) complexes are accessible, from which the most challenging bond-forming reactions can occur. Here we show the conceptual advantages of aryl thianthrenium salts for metallophotoredox catalysis, and their utility in site-selective late-stage aromatic fluorination.
- Li, Jiakun,Chen, Junting,Sang, Ruocheng,Ham, Won-Seok,Plutschack, Matthew B.,Berger, Florian,Chabbra, Sonia,Schnegg, Alexander,Genicot, Christophe,Ritter, Tobias
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- Hypervalent Iodine(III)-Catalyzed Balz–Schiemann Fluorination under Mild Conditions
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An unprecedented hypervalent iodine(III) catalyzed Balz–Schiemann reaction is described. In the presence of a hypervalent iodine compound, the fluorination reaction proceeds under mild conditions (25–60 °C), and features a wide substrate scope and good functional-group compatibility.
- Xing, Bo,Ni, Chuanfa,Hu, Jinbo
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p. 9896 - 9900
(2018/07/31)
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- Expanding the Balz–Schiemann Reaction: Organotrifluoroborates Serve as Competent Sources of Fluoride Ion for Fluoro-Dediazoniation
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The Balz–Schiemann reaction endures as a method for the preparation of (hetero)aryl fluorides yet is eschewed due to the need for harsh conditions or high temperatures along with the need to isolate potentially explosive diazonium salts. In a departure from these conditions, we show that various organotrifluoroborates (RBF3?s) may serve as fluoride ion sources for solution-phase fluoro-dediazoniation in organic solvents under mild conditions. This methodology was successfully extended to a one-pot process obviating aryl diazonium salt isolation. Sterically hindered (hetero)anilines are fluorinated under unprecedentedly mild conditions in good-to-excellent yields. Taken together, this work expands the repertoire of RBF3?s to act as fluorine ion sources in an update to the classic Balz–Schiemann reaction.
- Mohy El Dine, Tharwat,Sadek, Omar,Gras, Emmanuel,Perrin, David M.
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supporting information
p. 14933 - 14937
(2018/09/25)
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- Application of trivalent iodine compounds as catalysts in Bal-Schiemann reaction
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The invention discloses an application of trivalent iodine compounds shown in formula I and/or II in the description and used as catalysts in Bal-Schiemann reaction. The trivalent iodine compounds areused as the catalysts in the Bal-Schiemann reaction, so that the Bal-Schiemann reaction can be conducted at room temperature or near room temperature when a thermochemical method is used, and the reaction has mild reaction conditions, wide substrate use range and short reaction time, and is safe and easy to operate, products are easy to separate, and raw materials are simple and low in toxicity.
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Paragraph 0152; 0158
(2018/10/19)
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- Mechanistic investigations of Cu-catalyzed fluorination of diaryliodonium salts: Elaborating the CuI/CuIII manifold in copper catalysis
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A combination of experimental and density functional theory (DFT) investigations suggests that the Cu-catalyzed fluorination of unsymmetrical diaryliodonium salts with general structure [Mes(Ar)I]+ in N,N′-dimethylformamide proceeds through a CuI/CuIII catalytic cycle. A low concentration of fluoride relative to combined iodonium reagent plus copper ensures that [Mes(Ar)I]+ is available as the reactive species for oxidative "Ar+" transfer to a CuI center containing one or two fluoride ligands. A series of different possible CuI active catalysts (containing fluoride, triflate, and DMF ligands) have been evaluated computationally, and all show low-energy pathways to fluorinated products. The oxidation of these CuI species by [Mes(Ar)I]+ to form cis-Ar(F)CuIII intermediates is proposed to be rate-limiting in all cases. Ar-F bond-forming reductive elimination from CuIII is computed to be very facile in all of the systems examined. The conclusions of the DFT experiments are supported by several experimental studies, including tests showing that CuI is formed rapidly under the reaction conditions and that the fluoride concentration strongly impacts the reaction yields/selectivities.
- Ichiishi, Naoko,Canty, Allan J.,Yates, Brian F.,Sanford, Melanie S.
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supporting information
p. 5525 - 5534
(2015/02/19)
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- Cu-catalyzed fluorination of diaryliodonium salts with KF
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A mild Cu-catalyzed nucleophilic fluorination of unsymmetrical diaryliodonium salts with KF is described. This protocol preferentially fluorinates the smaller aromatic ligand on iodine(III). The reaction exhibits a broad substrate scope and proceeds with high chemoselectivity and functional group tolerance. DFT calculations implicate a CuI/CuIII catalytic cycle.
- Ichiishi, Naoko,Canty, Allan J.,Yates, Brian F.,Sanford, Melanie S.
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supporting information
p. 5134 - 5137
(2013/10/22)
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- Mild copper-mediated fluorination of aryl stannanes and aryl trifluoroborates
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This communication describes a mild copper-mediated fluorination of aryl stannanes and aryl trifluoroborates with N-fluoro-2,4,6-trimethylpyridinium triflate. This protocol demonstrates broad substrate scope and functional group tolerance, and does not require the use of any noble metal additives. The reaction is proposed to proceed via an arylcopper(III) fluoride intermediate.
- Ye, Yingda,Sanford, Melanie S.
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supporting information
p. 4648 - 4651
(2013/05/09)
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- Synthesis of functionalized aryl fluorides using organolithium reagents in flow microreactors
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Flow on: Flow microreactors enable the generation of aryl lithium compounds and subsequent electrophilic fluorination with NFSI and N-fluorosultam. The reaction can be successfully accomplished to synthesize various aryl fluorides involving an electron-withdrawing, an electron-donating, and a sterically hindered functional group in good yields. Copyright
- Nagaki, Aiichiro,Uesugi, Yuki,Kim, Heejin,Yoshida, Jun-Ichi
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supporting information
p. 705 - 708
(2013/05/08)
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- Mechanism of electrophilic fluorination with Pd(iv): Fluoride capture and subsequent oxidative fluoride transfer
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Electrophilic fluorinating reagents derived from fluoride are desirable for the synthesis of 18F-labeled molecules for positron emission tomography (PET). Here, we study the mechanism by which a Pd(iv)-complex captures fluoride and subsequently transfers it to nucleophiles. The intermediate Pd(iv)-F is formed with high rates even at the nano- to micromolar fluoride concentrations typical for radiosyntheses with 18F due to fast formation of an outer-sphere complex between fluoride and Pd(iv). The subsequent fluorine transfer from the Pd(iv)-F complex is proposed to proceed through an unusual SET/fluoride transfer/SET mechanism. The findings detailed in this manuscript provide a theoretical foundation suitable for addressing a more general approach for electrophilic fluorination with high specific activity 18F PET imaging.
- Brandt, Jochen R.,Lee, Eunsung,Boursalian, Gregory B.,Ritter, Tobias
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p. 169 - 179
(2014/01/06)
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- Silver-mediated fluorination of aryl silanes
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A regiospecific silver-mediated fluorination of aryl silanes is reported. The reaction is operationally simple, and employs Ag2O as readily available, inexpensive silver source, which can be recovered.
- Tang, Pingping,Ritter, Tobias
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supporting information; experimental part
p. 4449 - 4454
(2011/08/03)
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- Metal-Catalyzed Carbon-Fluorine Bond Formation
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One aspect of the invention relates to a metal-catalyzed conversion of aryl halides and sulfonates to the corresponding aryl fluorides. Another aspect of the invention relates to a metal-catalyzed conversion of heteroaryl halides and sulfonates to the corresponding heteroaryl fluorides. Another aspect of the invention relates to a metal-catalyzed conversion of vinyl halides and sulfonates to the corresponding vinyl fluorides. In certain embodiments, simple fluoride sources, such as AgF and CsF, are used. In certain embodiments, the transformations tolerate a wide range of functional groups, allowing for introduction of fluorine atoms into highly functionalized organic molecules.
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Page/Page column 18
(2011/02/18)
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- FLUORINATION OF ORGANIC COMPOUNDS
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Methods for fluorinating organic compounds are described herein.
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Page/Page column 63; 91; 104
(2010/07/10)
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- NO-CARRIER-ADDED NUCLEOPHILIC [F-18] FLUORINATION OF AROMATIC COMPOUNDS
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Phenyliodonium ylide derivatives substituted with electron donating as well as electron withdrawing groups on the aromatic ring are shown for use as precursors in aromatic nucleophilic substitution reactions. The iodonium ylide group is substituted by nucleophiles such as halide ions to provide the corresponding haloaryl derivatives. No- carrier-added [F-18]fluoride ion exclusively substitutes the iodonium ylide moiety in these derivatives and provides high specific activity F- 18 labeled fluoro derivatives. Protected L-dopa-6-iodonium ylide derivative have been synthesized as a precursors for the preparation of no-carrier-added 6-[F- 18]fluoro-L-dopa. The iodonium ylide group in this L-dopa.derivative is nucleophilically substituted by no-carrier-added [F-18]fluoride ion to provide a [F-18]fluoro intermediates which upon acid hydrolysis yielded 6-[F- 18]fluoro-L-dopa.
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Page/Page column 11-12
(2010/11/03)
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- Silver-catalyzed late-stage fluorination
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Carbon-fluorine bond formation by transition metal catalysis is difficult, and only a few methods for the synthesis of aryl fluorides have been developed. All reported transition-metal-catalyzed fluorination reactions for the synthesis of functionalized arenes are based on palladium. Here we present silver catalysis for carbon-fluorine bond formation. Our report is the first example of the use of the transition metal silver to form carbon-heteroatom bonds by cross-coupling catalysis. The functional group tolerance and substrate scope presented here have not been demonstrated for any other fluorination reaction to date.
- Tang, Pingping,Furuya, Takeru,Ritter, Tobias
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supporting information; experimental part
p. 12150 - 12154
(2010/10/04)
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- Large-scale preparation of aromatic fluorides via electrophilic fluorination with functionalized aryl- or heteroarylmagnesium reagents
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Functionalized aryl- or heteroarylmagnesium reagents, prepared from the corresponding bromides or iodides using halogen-magnesium exchange or direct magnesium insertion in the presence of lithium chloride, reacted smoothly with N-fluorobenzenesulfonimide, (PhSO2)2NF, in the mixed solvent (4:1 CH2Cl2-perfluorodecalin) to give the corresponding aromatic fluorides in moderate to good yields. Georg Thieme Verlag Stuttgart · New York.
- Yamada, Shigeyuki,Knochel, Paul
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experimental part
p. 2490 - 2494
(2010/09/04)
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- Convenient electrophilic fluorination of functionalized aryl and heteroaryl magnesium reagents
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"Chemical Equation Presented" Cive me an "F": Electrophilic fluorination of various aromatic and heteroaromatic Grignard reagents is smoothly performed with (PhSO2)2NF as fluorinating agent in a 4:1 mixture of CH2Cl2/ perfluorodecalin (see scheme). This solvent system allows minimization of most side reactions.
- Yamada, Shigeyuki,Gavryushin, Andrei,Knochel, Paul
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supporting information; experimental part
p. 2215 - 2218
(2010/06/19)
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- Efficient synthesis of aryl fluorides
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Chemical Equation Presented Creating C-F bonds: A novel electrophilic fluorination of aryl and heteroaryl Crignard reagents has been discovered and was used for the efficient synthesis of various aryl fluoride derivatives (see picture; THF = tetrahydrofuran).
- Anbarasan, Pazhamalai,Neumann, Helfried,Beller, Matthias
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experimental part
p. 2219 - 2222
(2010/06/17)
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- Fluorination of aromatic compounds with N-fluorobenzenesulfonimide under solvent-free conditions
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Reactions of N-fluorobenzenesulfonimide with methylbenzenes, phenols, and phenol ethers were studied under solvent-free conditions. The rate constant ratio for the reactions with mesitylene and durene indicates polar mechanism of the process. Solvent-free fluorination of aromatic compounds with N-fluorobenzenesulfonimide in some cases is more selective than reactions with other N-F reagents in a solvent.
- Andreev,Borodkin,Shubin
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scheme or table
p. 1468 - 1473
(2010/03/24)
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- Fluorination of boronic acids mediated by silver(I) Triflate
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A regiospecific Ag-mediated fluorination reaction of aryl- and alkenylboronic acids and esters Is reported. The fluorination reaction uses commercially available reagents, does not require the addition of exogenous ligands, and can be performed on a multigram scale. This report discloses the first practical reaction sequence from arylboronic acid to aryl fluorides.
- Furuya, Takeru,Ritter, Toblas
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supporting information; experimental part
p. 2860 - 2863
(2009/12/05)
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- A widely varying range of products in reactions of C6F5BrF2, C6F5IF2, and C6F5IF4 with Lewis acids of different strength
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The relative fluoride donor ability: C6F5BrF2 > C6F5IF2 > C6F5IF4 was outlined from reactions with Lewis acids of graduated strength in different solvents.
- Frohn, Hermann-Josef,Bailly, Frank,Welting, Dirk,Bardin, Vadim V.
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experimental part
p. 301 - 307
(2009/12/04)
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- Halo- and azidodediazoniation of arenediazonium tetrafluoroborates with trimethylsilyl halides and trimethylsilyl azide and Sandmeyer-type bromodediazoniation with Cu(I)Br in [BMIM][PF6] ionic liquid
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(Chemical Equation Presented) Reaction of [ArN2][BF4] salts immobilized in [BMIM][PF6] ionic liquid (IL) with TMSX (X = I, Br) and TMSN3 represents an efficient method for the preparation of iodo-, bromo-, and azido-derivatives via dediazoniation. The reactions can also be effected starting with ArNH2 by in situ diazotization with [NO][BF4] followed by reaction with TMSX or TMSN3. Depending on the substituents on the benzenediazonium cation, competing fluorodediazoniation (ArF formation) and hydrodediazoniation (ArH formation) were observed. Dediazoniation with TMSN3 and with TMSI generally gave the highest chemoselectivity toward ArN3 and ArI formation. The IL was recycled and reused up to 5 times with no appreciable decrease in the conversions. Multinuclear NMR monitoring of the interaction of [ArN 2][BF4]/TMSX, [BMIM][PF6]/TMSX, and [BMIM][PF6]/TMSX/[ArN2][BF4] indicated that TMSF is formed primarily via [ArN2][BF4]/ TMSX, generating [ArN2][X] in situ, which gives ArX on dediazoniation. Competing formation of ArF in Sandmeyer-type bromodediazoniation of [ArN 2][BF4] with Cu(I)Br immobilized in the IL points to significant involvement of heterolytic dediazoniation.
- Hubbard, Abigail,Okazaki, Takao,Laali, Kenneth K.
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p. 316 - 319
(2008/09/17)
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- Mechanism of electrophilic fluorination of aromatic compounds with NF-reagents
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Kinetic isotope effects H/D in electrophilic fluorination of aromatic compounds with NF-reagents were investigated. The small values of k H/k D (0.86-1.00) are in agreement with the polar reaction mechanism where the Wheland complex
- Borodkin,Zaikin,Shakirov,Shubin
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p. 1451 - 1459
(2008/09/16)
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- Arylation of anilines: formation of diarylamines using diaryliodonium salts
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Extensive studies on the reaction of the fluoride ion with diaryliodonium salts demonstrated that this is a generic process for the formation of fluoroarenes and has particular advantages for the preparation of fluorine-18 radiopharmaceuticals. During these studies it became apparent that nucleophiles other than the fluoride ion may be employed for generating substituted aromatics. This approach can be applied, using substituted anilines as the nucleophilic reagent, to the formation of a range of diarylamines in good yield. Optimised conditions for the reaction of a diaryliodonium salt with an aniline utilise TFA as the preferred counter-ion in DMF (130 °C, 24 h).
- Carroll, Michael A.,Wood, Reice A.
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p. 11349 - 11354
(2008/03/12)
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- N-(trifluoromethylsulfonyl)aryloxytrifluoromethylsulfoximines [ArO-SO(CF3)=NTf] and N-aryltriflimides Ar-N(Tf)2 by thermal and photolytic dediazoniation of [ArN2][BF4] in [BMIM][Tf2N] ionic liquid: Exploiting the ambident nucleophilic character of a "nonnucleophilic" anion
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(Chemical Equation Presented) Arenediazonium tetrafluoroborate salts undergo metathesis on immobilization in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonato)amide [BMIM][Tf2N]. The "noncoordinating", "nonnucleophilic" [Tf2N] anion acts as an ambident nucleophile toward the aryl cations, formed via thermal dediazoniation, to give predominantly the oxy anion quenching products [ArO-SO(CF3)=NTf], with minimal formation of ArN(Tf)2, irrespective of the nature of the substituent(s) on the ArN2 +. Strong preference for the formation of oxygen trapping products did not change under photolytic conditions, where dediazoniation occurs at room temperature. A minimal amount of the Schiemann product ArF is also formed in both thermal and photolytic dediazoniation, depending on the substituent(s). Progress of dediazoniation in the IL (both thermal and photolytic) and the evolution of the products were directly monitored by 1H and 19F NMR. According to DFT (Density Functional Theory) calculations, PhN(Tf)2 is more stable than PhO-SO(CF3)=NTf by 15-17 kcal/mol, depending on the basis set. Inclusion of solvation effects (PCM, with acetone and with CH2ClCH2Cl as solvent) did not change this preference. The [ArN2][BF4] dediazoniation in [BMIM][Tf2N] resulted in synthesis and characterization of a series of hitherto unknown [ArO-SO(CF3)=NTf] compounds. The X-ray structure of MesO-SO(CF3)=NTf (Mes = mesityl) is reported. On the basis of extraction studies, suitable solvent systems have been identified that remove the products without dissolving [BMIM][NTf2], thus overcoming product recovery difficulties typically associated with the use of this IL.
- Laali, Kenneth K.,Okazaki, Takao,Bunge, Scott D.
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p. 6758 - 6762
(2008/02/10)
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- Electrophilic fluorination of aromatic compounds with NF type reagents: Kinetic isotope effects and mechanism
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H/D Isotope effects in fluorination of aromatic compounds with NF type reagents have been studied to reveal the reaction mechanism. The results obtained are consistent with a polar SEAr mechanism. Small deuterium isotope effects (kH/
- Borodkin, Gennady I.,Zaikin, Pavel A.,Shubin, Vyacheslav G.
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p. 2639 - 2642
(2007/10/03)
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- First application of ionic liquids in electrophilic fluorination of arenes; Selectfluor (F-TEDA-BF4) for "green" fluorination
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The NF fluorinating agent F-TEDA-BF4 dication salt (Selectfluor) 1 dissolves in imidazolium-based ionic liquids [emim][OTf] 7, [emim][BF4] 8, [bmim][PF6] 9 and [bmim][BF4] 10 (assisted by sonication), providing a convenient medium for fluorination of arenes under essentially acid-free conditions in a simple set-up (no volatile solvent; simple extraction of the aromatics without aqueous work-up), from which the ionic liquid can be easily recycled and reused. Comparative studies in [emim][OTf] 7 with anisole as substrate show that 1 is superior to NFTh-BF4 (Accufluor) 2 and that the N-fluoropyridinium salt NFPy-B2F7 4 is least effective. The scope of the reaction has been surveyed. Substrate selectivity (k mesitylene: k durene = 10) measured in competitive experiments in 7 is clearly indicative of a conventional polar mechanism. Substrate selectivity measured without the ionic liquid in MeCN solvent is also indicative of a polar mechanism but exhibits lower magnitude (k mesitylene: kdurene = 6). Addition of dicyclohexano-24-crown-8 to the fluorination reaction mixture (1 and anisole) in 7 reduced the conversion but did not change the isomer distribution. AM1 minimization was used to model the complexation of 1 with this crown. With reactive aromatics optimal fluorination yields in ionic liquids (using 1 equivalent of the NF reagent) are around 50% (higher for naphthalene). A key control experiment suggests that the free base (produced upon transfer-fluorination) could complex to unreacted 1 (generating a bulky dimer complex which may be ineffective for fluorine transfer) in competition to N-protonation.
- Laali, Kenneth K.,Borodkin, Gennady I.
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p. 953 - 957
(2007/10/03)
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- Exploratory study of the reaction of bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor reagent) with diaryl sulfoxides: Novel routes to Ar2SF2 and Ar2SF(OTf) via sulfoxide activation
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Neither bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor reagent) nor HF/pyridine alone can fluorinate diaryl sulfoxides. S-fluorination can be effected by activating the sulfoxide via protonation with HF/pyridine (70:30) to form sulfoxonium ions in
- Laali, Kenneth K.,Borodkin, Gennady I.
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p. 169 - 173
(2007/10/03)
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- Fluorodediazoniation in ionic liquid solvents: New life for the Balz-Schiemann reaction
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Drawbacks associated with the classic Balz-Schiemann reaction are eliminated in a series of examples by conducting fluorodediazoniation in ionic liquid solvents, thus opening up a new horizon for a much in demand process.
- Laali, Kenneth K.,Gettwert, Volker J.
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- Process for the preparation of fluoro compounds from the corresponding amines
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Compounds containing a primary amino group are converted into compounds containing a fluorine atom in place of the amino group by reaction of the amino compound with hydrogen fluoride and a nitrosating reagent under the influence of ultrasound or microwaves.
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- Electrophilic fluorination of aromatics with selectfluor and trifluoromethanesulfonic acid 1
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1-(chloromethyl)-4-fluoro-1,4-diazabicyclo[2.2.2]octane bis (tetrafluoroborate) [Selectfluor F-TEDA-BF4 (TEDA = triethylenediamine)] in the presence of trifluoromethanesulfonic acid has been found to be a very effective reagent system for the direct electrophilic fluorination of a wide variety of aromatic compounds under mild reaction conditions to the corresponding fluoroaromatics in good to excellent yields.
- Shamma, Tatyana,Buchholz, Herwig,Prakash, G. K. Surya,Olah, George A.
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p. 207 - 210
(2007/10/03)
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- Process for preparing o-alkylfluorobenzenes
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o-Alkylfluorobenzenes are advantageously prepared by heating the corresponding chloroformates to from 70° to 200° C. in the liquid phase in the presence of hydrogen fluoride and in the presence of an inert diluent other than a halogenated alkane.
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- The synthesis of [18F]fluoroarenes from the reaction of cyclotron-produced [18F]fluoride ion with diaryliodonium salts
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Diaryliodonium salts have been shown to react with fluoride ion at 80°C in acetonitrile to generate aryl fluorides. The regioselectivity is controlled electronically and by the bulk of the ortho-substituents on the rings, with the latter the dominant factor such that electron-rich rings can be fluorinated. ortho-Substituted aryl fluorides can be selectively produced from unsymmetrical diaryliodonium salts. The process has been used to synthesise [18F] labelled aromatics by the use of cyclotron generated [18F]fluoride ion.
- Shah, Aneela,Pike, Victor W.,Widdowson, David A.
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p. 2043 - 2046
(2007/10/03)
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- Liquid-Phase Decarboxylation of Aromatic Haloformates: A New Access to Chloro- and Fluoroaromatics
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The treatment of phenyl chloroformates 1 with a Lewis acid in the liquid phase resulted in decarboxylation to the corresponding chloroaromatics 2. Fluoroaromatic compounds were synthesized from phenylchloroformates 1 through a sequential fluorination/decarboxylation in the liquid phase by treatment with excess anhydrous hydrogen fluoride under mild conditions. In all cases, yields were increased by performing the reaction in 1,2,4-trichlorobenzene, which is inert to Friedel-Crafts reactions.
- Lui, Norbert,Marhold, Albrecht,Rock, Michael H.
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p. 2493 - 2496
(2007/10/03)
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- Aryl fluoride syntheses involving reactions of aryllead triacetates with boron trifluoride-diethyl ether complex
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Aryllead(IV) triacetates react at room temperature with BF3.Et2O to give the corresponding aryl fluoride in moderate to good yields; triarylboroxines, electron rich aryltrimethylsilanes and some arenes, which yield aryllead triacetates in acid catalysed reactions with lead tetraacetate, are converted directly into aryl fluorides when stirred with lead tetraacetate in BF3.Et2O. An investigation of the mechanism of the fluoro-deplumbation reaction indicates that it probably proceeds by acid catalysed heterolytic cleavage of the C-Pb bond to produce an aryl cation.
- De Meio,Morgan,Pinhey
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p. 8129 - 8138
(2007/10/02)
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- Organic fluorides from fluoroformic esters
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A method for the preparation of an organic fluoride by contacting a fluoroformic acid ester with alumina at a temperature in the range 200°-600° C.
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- THE PREPARATION OF FLUOROARENES BY THE CATALYTIC DECARBOXYLATION OF ARYL FLUOROFORMATES
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The catalytic decarboxylation of phenyl fluoroformate to fluorobenzene has been achieved with yields of 70-80percent in a flow system using alumina or alumina-based catalysts.The reaction occurs in short space times (Pd/Al2O3>Rh/Al2O3 ca.Al2O3. 2,4,6-Trimethylphenyl fluoroformate, a new material, was found to decarboxylate similarly to give 1-fluoro-2,4,6-trimethylbenzene, but 4-chlorophenyl fluoroformate was noted to produce only low yields (ca. 10percent) of the corresponding aryl fluoride.
- Ashton, David P.,Ryan, Anthony T.,Webster, Brian R.,Wolfindale, Brett A.
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p. 263 - 274
(2007/10/02)
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- Effect of Catalyst on the Fluorination of Methyl-Substituted Benzenes with Xenon Difluoride
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The course of acid-catalyzed liquid-phase fluorination of methyl-substituted benzene derivatives with xenon difluoride depends strongly on the structure and concentration of the substrate, its molar ratio to xenon difuoride, and the catalyst.HF-catalyzed
- Stavber, Stojan,Zupan, Marko
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p. 2223 - 2226
(2007/10/02)
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- 167. Dediazoniation of Arenediazonium Ions. Part XXII. Reactions of 2,6-Dialkyl-Substituted Benzenediazonium Ions in Super Acids. Acetonitrile and Acetone
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Reactions of 2,4,6-trimethylbenzenediazonium (1), 2,6-diethylbenzenediazonium (2) and 2,6-diisopropylbenzenediazonium (3) tetrafluoroborates were studied in magic acid, SbF5/SO2ClF, acetonitrile and acetone by 1H-NMR and by analysis of the dediazoniation products.The Nα-Nβ rearrangement of β-N15-labelled tetrafluoroborates 1-3 was followed by 15N-NMR of the corresponding arylazonaphthols, as well as by MS analysis of the anilines obtained by reduction of the azo compounds.Diazonium salts 2 and 3 were synthesized for the first time and the steric effect substituents at C(2) and C(6) on the reactions under study is discussed.All the results obtained can be rationalized by heterolytic dediazoniation of diazonium salts 1-3 and product formation from the corresponding aryl cations.
- Laali, Khosrow,Szele, Ivanka,Zollinger, Heinrich
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p. 1737 - 1747
(2007/10/02)
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