- Metal-Free Photoredox-Catalyzed Hydrodefluorination of Fluoroarenes Utilizing Amide Solvent as Reductant
-
A metal-free photoredox-catalyzed hydrodefluorination of fluoroarenes was achieved by using N,N,N’,N’-tetramethyl-para-phenylenediamine (1) as a strong photoreduction catalyst. This reaction was applicable not only to electron-rich monofluoroarenes but also to polyfluoroarenes to afford non-fluorinated arenes. The experimental mechanistic studies indicated that the amide solvent NMP plays an important role for regeneration of the photocatalyst, enabling additive-free photoreduction catalysis.
- Toriumi, Naoyuki,Yamashita, Kazuya,Iwasawa, Nobuharu
-
supporting information
p. 12635 - 12641
(2021/08/03)
-
- Radical Decarboxylative Carbometalation of Benzoic Acids: A Solution to Aromatic Decarboxylative Fluorination
-
Abundant aromatic carboxylic acids exist in great structural diversity from nature and synthesis. To date, the synthetically valuable decarboxylative functionalization of benzoic acids is realized mainly by transition-metal-catalyzed decarboxylative cross couplings. However, the high activation barrier for thermal decarboxylative carbometalation that often requires 140 °C reaction temperature limits both the substrate scope as well as the scope of suitable reactions that can sustain such conditions. Numerous reactions, for example, decarboxylative fluorination that is well developed for aliphatic carboxylic acids, are out of reach for the aromatic counterparts with current reaction chemistry. Here, we report a conceptually different approach through a low-barrier photoinduced ligand to metal charge transfer (LMCT)-enabled radical decarboxylative carbometalation strategy, which generates a putative high-valent arylcopper(III) complex, from which versatile facile reductive eliminations can occur. We demonstrate the suitability of our new approach to address previously unrealized general decarboxylative fluorination of benzoic acids.
- Xu, Peng,López-Rojas, Priscila,Ritter, Tobias
-
supporting information
p. 5349 - 5354
(2021/05/05)
-
- Nucleophilic Fluorination of Heteroaryl Chlorides and Aryl Triflates Enabled by Cooperative Catalysis
-
Aryl and heteroaryl fluorides are growing to be dominant motifs in pharmaceuticals and agrochemicals, yet they are rare in both nature and commodity chemicals. As a consequence, there is an increasingly urgent need to develop mild, cost-effective, and scalable methods for fluorination. The most straightforward route to synthesize aryl fluorides is through the halide exchange "halex"reaction, but conditions, cost, and atom economy preclude most available methods from large-scale manufacturing processes. We report a new approach that leverages the cooperative action of 18-crown-6 ether and tetramethylammonium chloride to catalytically access the reactivity of tetramethylammonium fluoride and achieve halex fluorinations under mild conditions with operational ease. The described methodology readily converts both heteroaryl chlorides and aryl triflates to their corresponding (hetero)aryl fluorides in high yields and purities.
- Hong, Cynthia M.,Whittaker, Aaron M.,Schultz, Danielle M.
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p. 3999 - 4006
(2021/03/09)
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- Fluorination of arylboronic esters enabled by bismuth redox catalysis
-
Bismuth catalysis has traditionally relied on the Lewis acidic properties of the element in a fixed oxidation state. In this paper, we report a series of bismuth complexes that can undergo oxidative addition, reductive elimination, and transmetallation in a manner akin to transition metals. Rational ligand optimization featuring a sulfoximine moiety produced an active catalyst for the fluorination of aryl boronic esters through a bismuth (III)/bismuth (V) redox cycle. Crystallographic characterization of the different bismuth species involved, together with a mechanistic investigation of the carbonfluorine bond-forming event, identified the crucial features that were combined to implement the full catalytic cycle.
- Planas, Oriol,Wang, Feng,Leutzsch, Markus,Cornella, Josep
-
p. 313 - 317
(2020/01/28)
-
- Novel manufacturing method of fluoro-aryl compounds and derivatives thereof
-
The invention relates to a novel method of manufacturing fluoro-aryl compounds and derivatives thereof, in particular, fluorobenzene and derivatives thereof. The production environment of the manufacturing method is environmentally friendly. The shortages of a conventional method are overcome through a simple and beneficial mode. Compared with the prior art, the provided method is more effective,more environmentally friendly, and more energy saving. The method is used to produce core fluorinated aromatic compounds, preferably, core fluorinated fluorobenzene. On one aspect, the invention provides a method, which is advantages in industry and uses HF and a halogenated benzene precursor to prepare fluorobenzene and hydrogen halide. Moreover, the invention provides chlorobenzene as the primary raw material to prepare fluorobenzene, which is an important material in industry, and a beneficial, unexpected and simple application of chlorobenzene. In the prior art, the provided application ofchlorobenzene is unknown.
- -
-
Paragraph 0225-0228; 0229-0230
(2020/01/25)
-
- Base-Catalyzed Aryl-B(OH)2 Protodeboronation Revisited: From Concerted Proton Transfer to Liberation of a Transient Aryl Anion
-
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.
- 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)
-
- Catalytic Hydrodefluorination of Fluoroarenes Using Ru(IMe4)2L2H2 (IMe4 = 1,3,4,5-Tetramethylimidazol-2-ylidene; L2 = (PPh3)2, dppe, dppp, dppm) Complexes
-
The all-trans isomer of Ru(IMe4)2(PPh3)2H2 (ttt-4; IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) reacts with C6F6 at 70 °C to afford the hydride fluoride complex Ru(IMe4)2(PPh3)2HF (ttt-6). At room temperature, ttt-6 reacts with Et3SiH to give a mixture of products, one of which is assigned as the silyl trihydride complex Ru(IMe4)2(PPh3)(SiEt3)H3 (8) by comparison to the isolated and structurally characterized analogue Ru(IMe4)2(PPh3)(SiPh3)H3 (9). As ttt-4 was re-formed cleanly upon heating ttt-6 with Et3SiH, it was tested in the catalytic hydrodefluorination (HDF) of C6F6 (10 mol %, 90 °C), along with 9, Ru(IMe4)2(P-P)HF (P-P = Ph2P(CH2)2PPh2 (dppe, cct-13), Ph2P(CH2)3PPh2 (dppp, cct-14), Ph2PCH2PPh2 (dppm, cct-15)), Ru(IEt2Me2)2(PPh3)2HF (cct-7; IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)), and Ru(IEt2Me2)2(dppe)2HF (cct-16) for comparison. Both cct-13 and cct-14 brought about near-quantitative conversion to C6FH5 in 24 h, in comparison to ca. 50% conversion with ttt-4 in 144 h.
- Cybulski, Mateusz K.,Nicholls, Jessica E.,Lowe, John P.,Mahon, Mary F.,Whittlesey, Michael K.
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p. 2308 - 2316
(2017/06/30)
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- Room Temperature Regioselective Catalytic Hydrodefluorination of Fluoroarenes with trans-[Ru(NHC)4H2] through a Concerted Nucleophilic Ru?H Attack Pathway
-
The efficient and highly selective room temperature hydrodefluorination (HDF) of fluoroarenes by the trans-[Ru(IMe4)4H2] catalyst, 3, is reported. Mechanistic studies show 3 acts directly in catalysis without any ligand dissociation and DFT calculations indicate a concerted nucleophilic attack mechanism. The calculations fully account for the observed selectivities which corroborate earlier predictions regarding the selectivity of HDF.
- Cybulski, Mateusz K.,McKay, David,Macgregor, Stuart A.,Mahon, Mary F.,Whittlesey, Michael K.
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p. 1515 - 1519
(2017/02/05)
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- Method for preparing difluorobenzene by tubular diazotization reaction
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A method for preparing difluorobenzene by a tubular diazotization reaction comprises the following steps: mixing a material phenylenediamine, a hydrochloric acid aqueous solution and a fluorboric acid aqueous solution and storing the mixture into a first storage tank, storing a material sodium nitrite aqueous solution into a second storage tank, respectively conveying the above materials into a mixer through a transfer pump and mixing and adding the mixture into a tubular reactor, carrying out a diazotization reaction at 0-100 DEG C for reaction residence time of 1-150 s, cooling the reaction mixture obtained after the reaction to minus 5-minus 10 DEG C, filtering to obtain wet diazonium salt and a filtrate, drying the wet diazonium salt, pyrolyzing by a pyrolysis kettle, collecting a target fraction, and distilling to obtain difluorobenzene. The method of the invention has advantages of high product yield, less ''three wastes (waste gas, waste water and industrial residue) '', simple operation and good safety, and is very suitable for industrial production.
- -
-
Paragraph 0024; 0025; 0026; 0027; 0028; 0029
(2017/05/27)
-
- Synthesis and characterization of a novel N-F reagent derived from the ethano-Tr?ger's base: 1JFN coupling constants as a signature for the N-F bond
-
Methylation of 2,8-dimethyl-6H,12H-5,11-ethanodibenzo[b,f][1,5]-diazocine (ethano-Tr?ger's base) with methyl iodide followed by ion metathesis and fluorination with N-fluoro-2,3,4,5,6-pentachloropyridinium triflate affords a new electrophilic N-F reagent, that is more reactive than Selectfluor. 2D 19F-15N HMQC experiments provide 1JNF coupling constants which are diagnostic for the N-F functional group.
- Pereira, Raul,Wolstenhulme, Jamie,Sandford, Graham,Claridge, Timothy D. W.,Gouverneur, Véronique,Cvengro?, Ján
-
supporting information
p. 1606 - 1609
(2016/01/30)
-
- Copper-Mediated Radiofluorination of Arylstannanes with [18F]KF
-
A copper-mediated nucleophilic radiofluorination of aryl- and vinylstannanes with [18F]KF is described. This method is fast, uses commercially available reagents, and is compatible with both electron-rich and electron-deficient arene substrates. This method has been applied to the manual synthesis of a variety of clinically relevant radiotracers including protected [18F]F-phenylalanine and [18F]F-DOPA. In addition, an automated synthesis of [18F]MPPF is demonstrated that delivers a clinically validated dose of 200 ± 20 mCi with a high specific activity of 2400 ± 900 Ci/mmol.
- Makaravage, Katarina J.,Brooks, Allen F.,Mossine, Andrew V.,Sanford, Melanie S.,Scott, Peter J. H.
-
supporting information
p. 5440 - 5443
(2016/11/04)
-
- Hydrodefluorination of fluoroaromatics by isopropyl alcohol catalyzed by a ruthenium NHC complex. An unusual role of the carbene ligand
-
The NHC (NHC = N-heterocyclic carbene) complex Cp*(IPr)RuH3 catalyzes hydrodefluorination of aromatic fluorides at 70 °C with isopropyl alcohol as the reducing reagent. The reaction is selective for aromatic fluorides, as almost negligible C(sp3)?F bond reduction takes place. The activity decreases from more to less fluorinated substrates, but polyaromatic monofluorides, such as 1-fluoronaphthalene and 6-fluoro-2-methylquinoline, can also be reduced in moderate to good yields. Kinetic studies are consistent with a mechanism based on elimination of NHC and reversible substrate coordination, followed by coordination of the alcohol.
- Mai, Van Hung,Nikonov, Georgii I.
-
p. 7956 - 7961
(2018/05/23)
-
- Reactions of aromatic compounds with xenon difluoride
-
Reactions of substituted benzenes C6H5R (R = Me, F, Cl, Br, CF3, NO2) with xenon difluoride in the presence of boron trifluoride–diethyl ether complex in weakly acidic (1,1,1,3,3-pentafluorobutane) and weakly basic media (acetonitrile) have been studied. These reactions lead to the formation of fluorobenzene derivatives FC6H4R (isomer mixture) together with isomeric difluorobenzenes and fluorinated and non-fluorinated biphenyls. The results have been compared with previously reported data obtained in other solvents using other catalysts.
- Bardin,Adonin, N. Yu.
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p. 1400 - 1407
(2016/11/29)
-
- Stoichiometric and catalytic C-F bond activation by the trans-dihydride NHC complex [Ru(IEt2Me2)2-(PPh3)2H2] (IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)
-
The room temperature reaction of C6F6 or C6F5H with [Ru(IEt2Me2)2(PPh3)2H2] (1; IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) generated a mixture of the trans-hydride fluoride complex [Ru(IEt2Me2)2(PPh3)2HF] (2) and the bis-carbene pentafluorophenyl species [Ru(IEt2Me2)2(PPh3)(C6F5)H] (3). The formation of 3 resulted from C-H activation of C6F5H (formed from C6F6via stoichiometric hydrodefluorination), a process which could be reversed by working under 4 atm H2. Upon heating 1 with C6F5H, the bis-phosphine derivative [Ru(IEt2Me2)(PPh3)2(C6F5)H] (4) was isolated. A more efficient route to 2 involved treatment of 1 with 0.33 eq. of TREAT-HF (Et3N·3HF); excess reagent gave instead the [H2F3]- salt (5) of the known cation [Ru(IEt2Me2)2(PPh3)2H]+. Under catalytic conditions, 1 proved to be an active precursor for hydrodefluorination, converting C6F6 to a mixture of tri, di and monofluorobenzenes (TON = 37) at 363 K with 10 mol% 1 and Et3SiH as the reductant.
- Cybulski, Mateusz K.,Riddlestone, Ian M.,Mahon, Mary F.,Woodman, Timothy J.,Whittlesey, Michael K.
-
p. 19597 - 19605
(2015/11/27)
-
- Rhodium catalyzed, carbon-hydrogen bond directed hydrodefluorination of fluoroarenes
-
[CpRhCl(μ-Cl)]2 is reported as a highly efficient and selective precatalyst for the hydrodefluorination of perfluoroarenes using a hydrocarbon-soluble aluminum dihydride as the terminal reductant. Reactions are directed to cleave a C-F bond adjacent to an existing C-H bond with high regioselectivity (98.5-99%). A heterobimetallic complex containing an extremely rare Al-H-Rh functional group has been isolated and shown to be catalytically competent.
- Ekkert, Olga,Strudley, Sebastian D. A.,Rozenfeld, Alisa,White, Andrew J. P.,Crimmin, Mark R.
-
supporting information
p. 7027 - 7030
(2015/05/19)
-
- Synthesis of aryl fluorides from potassium aryltrifluoroborates and selectfluor mediated by iron(III) chloride
-
The synthesis of fluorinated arenes by the iron-mediated fluorination of potassium aryltrifluoroborates with Selectfluor and potassium fluoride is described. The fluorination reaction uses commercially available reagents and without requiring the addition
- Dubbaka, Srinivas Reddy,Gadde, Satyanarayana,Narreddula, Venkateswara Reddy
-
p. 854 - 860
(2015/03/14)
-
- FLUORINATION OF ARYL COMPOUNDS
-
The invention provides compositions and methods of using the compositions in fluorinating aryl precursors containing a leaving group replaceable by a fluorine atom. The compositions include a metal ion source, a electrophilic fluorine source, a base, and a compound, which is an aryl precursor of the aryl fluoride, and which has a leaving group replaceable by the fluorine atom. Exemplary methods of the invention make use of such compositions and methods to prepare an aryl fluoride compound. In an exemplary embodiment, the electrophilic fluorine source is a source of 18F.
- -
-
Paragraph 00117; 00118-00121
(2014/07/22)
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- Silver-mediated fluorination of potassium aryltrifluoroborates with Selectfluor Dedicated to Professor Andrea Vasella on the occasion of his 71st birthday
-
A simple and practical procedure for the silver-mediated fluorination of aryl- and heteroaryltrifluoroborates with electrophilic fluorine from Selectfluor and LiOH·H2O is presented. The reaction procedure is simple and easy to set up, the process produces fluorinated arenes and heteroarenes in good to excellent yields and a wide range of electronically and structurally diverse substrates are tolerated.
- Dubbaka, Srinivas Reddy,Narreddula, Venkateswara Reddy,Gadde, Satyanarayana,Mathew, Thresen
-
p. 9676 - 9681
(2015/01/08)
-
- Mild copper-mediated fluorination of aryl stannanes and aryl trifluoroborates
-
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.
-
supporting information
p. 4648 - 4651
(2013/05/09)
-
- Copper-mediated fluorination of arylboronate esters. Identification of a Copper(III) fluoride complex
-
A method for the direct conversion of arylboronate esters to aryl fluorides under mild conditions with readily available reagents is reported. Tandem reactions have also been developed for the fluorination of arenes and aryl bromides through arylboronate ester intermediates. Mechanistic studies suggest that this fluorination reaction occurs through facile oxidation of Cu(I) to Cu(III), followed by rate-limiting transmetalation of a bound arylboronate to Cu(III). Fast C-F reductive elimination is proposed to occur from an aryl-copper(III)-fluoride complex. Cu(III) intermediates have been generated independently and identified by NMR spectroscopy and ESI-MS.
- Fier, Patrick S.,Luo, Jingwei,Hartwig, John F.
-
p. 2552 - 2559
(2013/03/29)
-
- Cu(OTf)2-mediated fluorination of aryltrifluoroborates with potassium fluoride
-
This Communication describes the Cu(OTf)2-mediated fluorination of aryltrifluoroborates with KF. The reaction proceeds under mild conditions (at 60 C over 20 h) and shows a broad substrate scope and functional group tolerance. The Cu is proposed to play two separate roles in this transformation: (1) as a mediator for the aryl-F coupling and (2) as an oxidant for accessing a proposed CuIII(aryl)(F) intermediate.
- Ye, Yingda,Schimler, Sydonie D.,Hanley, Patrick S.,Sanford, Melanie S.
-
supporting information
p. 16292 - 16295
(2013/12/04)
-
- Thermal decomposition of 4-fluorobenzenediazonium perfluoroorganyl(fluoro) borates, [4-FC6H4N2]Y (Y = RFBF 3 (RF = C6F5, C6F 13, trans-C4F9CFCF, cis-C6F 13CFCF, CF3CC) and (C6F13) 2BF2)
-
Heating of the neat salts [4-FC6H4N 2][RFBF3] (RF = C6F 5, C6F13, trans-C4F9CFCF, cis-C6F13CFCF, CF3CC) or in solid mixtures with NaF gives the principal product 1,4-C6F2H4 besides RFBF2 or Na[RFBF3], respectively. Thermolysis of [4-FC6H4N2] [(C6F13)2BF2] in NaF results in 1,4-C6F2H4, Na[BF4], Na[(C 6F13)2BF2], and a new type of product, the isomer Na[C6F13CF(BF3)C 5F11].
- Bardin, Vadim V.,Frohn, Hermann-Josef
-
p. 333 - 338
(2014/01/06)
-
- Cu-catalyzed fluorination of diaryliodonium salts with KF
-
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.
-
supporting information
p. 5134 - 5137
(2013/10/22)
-
- Palladium(III)-catalyzed fluorination of arylboronic acid derivatives
-
A practical, palladium-catalyzed synthesis of aryl fluorides from arylboronic acid derivatives is presented. The reaction is operationally simple and amenable to multigram-scale synthesis. Evaluation of the reaction mechanism suggests a single-electron-transfer pathway, involving a Pd(III) intermediate that has been isolated and characterized.
- Mazzotti, Anthony R.,Campbell, Michael G.,Tang, Pingping,Murphy, Jennifer M.,Ritter, Tobias
-
supporting information
p. 14012 - 14015
(2013/10/21)
-
- FLUORINATION OF ORGANIC COMPOUNDS
-
Methods for fluorinating organic compounds are described herein.
- -
-
Page/Page column 25
(2012/11/06)
-
- Reaction of organylxenonium(II)salts, [RXe][Y], with organyl iodides, R'I, in anhydrous HF: Scope and limitation of a new synthetic approach to iodonium salts, [RR'I][Y]
-
Perfluoroalkynylxenonium salts, [RXe][BF4] (R = CF 3C≡C, (CF3)22CFC≡C), reacted with organyl iodides, R'I (R' = 3-FC6H4, C6F 5, CF2 ≡CF, CF3CH2; no reaction with R' = CF3CF2CF2)in anhydrous HF to yield the corresponding asymmetric polyfluorinated iodonium salts, [RR'I][Y]. The action of the arylxenonium salt, [C6F5Xe]-[BF4], and the cycloalkenylxenonium salt, [cyclo-1,4-C6F7Xe]-[AsF6], on 4-FC6H4I gave [C6F5(4-FC 6H4)I][BF4] and [cyclo-1,4-C 6F7(4-FC6H4)I][AsF6], respectively, besides the symmetric iodonium salt, [(4-FC6H4)2 2I][Y]. But the aryl-, as well as the cycloalkenylxenonium salt, did not react with C6F5I, CF2 =CFI, and CF 3CH2I.
- Frohn, Hermann-Josef,Bardin, Vadim V.
-
experimental part
p. 2616 - 2620
(2012/05/31)
-
- Decisive steps of the hydrodefluorination of fluoroaromatics using [Ni(NHC)2]
-
The hydrodefluorination reaction of perfluorinated arenes using [Ni 2(iPr2Im)4(COD)] (1; iPr2Im = 1,3-bis(isopropyl)imidazolin-2-ylidene) as a catalyst as well as stoichiometric transformations to elucidate the decisive steps for this reaction are reported. The reaction of hexafluorobenzene with 5 equiv of triphenylsilane in the presence of 5 mol % of 1 affords 1,2,4,5-tetrafluorobenzene after 48 h at 60 °C and 1,4-difluorobenzene after 96 h at 80 °C; the reaction of perfluorotoluene and 5 equiv of Et 3SiH for 4 days at 80 °C results in the selective formation of 1-(CF3)-2,3,5,6-C6F4H. Stoichiometric transformations of the complexes cis-[Ni(iPr2Im) 2(H)(SiPh3)] and cis-[Ni(iPr 2Im)2(H)(SiMePh2)] with hexafluorobenzene at room temperature lead to the formation of trans-[Ni(iPr 2Im)2(F)(C6F5)] (2) and trans-[Ni(iPr2Im)2(H)(C6F 5)] (4) with elimination of the corresponding silane or fluorosilane. The reactions of the C-F activation products trans-[Ni(iPr 2Im)2(F)(C6F5)] (2) and trans-[Ni(iPr2Im)2(F)(4-(CF3)C 6F4)] (3) with PhSiH3 and Ph 2SiH2 afford the hydride complexes trans-[Ni( iPr2Im)2(H)(C6F5)] (4) and trans-[Ni(iPr2Im)2(H)(4-(CF 3)C6F4)] (5), which convert into the compounds trans-[Ni(iPr2Im)2(F)(2,3,5,6-C 6F4H)] (7), trans-[Ni(iPr2Im) 2(F)(3-(CF3)-2,4,5-C6F3H)] (9a), and trans-[Ni(iPr2Im)2(F)(2-(CF 3)-3,4,6-C6F3H)] (9b), respectively. In the case of the rearrangement of trans-[Ni(iPr2Im) 2(H)(4-(CF3)C6F4)] (5) the intermediate [Ni(iPr2Im)2(η2-C, C-(CF3)C6F4H)] (8) was detected. Reaction of 8 with perfluorotoluene gave the C-F activation product trans-[Ni( iPr2Im)2(F)(4-(CF3)C 6F4)] (3). All these experimental findings point to a mechanism for the HDF by [Ni(iPr2Im)2] via the "fluoride route" involving C-F activation of the polyfluoroarene, H/F exchange of the resulting nickel fluoride, reductive elimination of the polyfluoroaryl nickel hydride to an intermediate with a η2-C,C- coordinated arene ligand, subsequent ligand exchange with the higher fluorinated polyfluoroarene, and renewed C-F activation of the polyfluoroarene. Without additional reagents, [Ni(iPr2Im)2(η 2-C,C-(CF3)C6F4H)] (8) rearranges to the isomers trans-[Ni(iPr2Im)2(F)(3-(CF 3)-2,4,5-C6F3H)] (9a; major) and trans-[Ni(iPr2Im)2(F)(2-(CF3)-3,4,6- C6F3H)] (9b; minor) in a ratio of 80:20. DFT calculations performed on conversion of trans-[Ni(iPr2Im) 2(H)(4-(CF3)C6F4)] 5 into the two products trans-[Ni(iPr2Im)2(F)(3-(CF 3)-2,4,5-C6F3H)] 9a and trans-[Ni( iPr2Im)2(F)(2-(CF3)-3,4,6-C 6F3H)] (9b) using the commonly accepted intramolecular concerted pathway via η2-C,F-σ-bound transition states predict 9b to be the major product. We thus propose that this reaction mechanism is not valid for the [Ni(NHC)2]-mediated C-F activation of partially fluorinated arenes with special substitution patterns.
- Fischer, Peter,Goetz, Kathrin,Eichhorn, Antonius,Radius, Udo
-
experimental part
p. 1374 - 1383
(2012/04/10)
-
- Ipso-Fluorination of aryltrimethylsilanes using xenon difluoride
-
Reaction of aryltrimethylsilanes with xenon difluoride in C 6F6/Pyrex at room temperature gives aryl fluorides in good yield. The reaction is inhibited when acetonitrile is used as solvent but proceeds well in CFCl3/Pyrex or CH 2Cl2/Pyrex. Pyrex appears to be a very effective heterogeneous catalyst for this ipso-fluorination. The reaction does not proceed in PTFE, quartz, soda glass or glassy-carbon flasks or Pyrex flasks pre-rinsed with 2 M NaOH. Aryltrimethylstannanes and arylboronic acids and their esters do not undergo ipso-fluorination under similar conditions. Plausible mechanisms involving electrophilic addition of polarised xenon difluoride [FXeδ+?F→Pyrex δ-] followed by ligand coupling are discussed.
- Lothian, Aileen P.,Ramsden, Christopher A.,Shaw, Maxine M.,Smith, Rachel G.
-
experimental part
p. 2788 - 2793
(2011/05/02)
-
- Silver-mediated trifluoromethoxylation of aryl stannanes and arylboronic acids
-
A silver-mediated cross-coupling of trifluoromethoxide with aryl stannanes and arylboronic acids to give aryl trifluoromethyl ethers is reported. This is the first report of a transition-metal-mediated Caryl-OCF3 bond formation.
- Huang, Chenghong,Liang, Theresa,Harada, Shinji,Lee, Eunsung,Ritter, Tobias
-
experimental part
p. 13308 - 13310
(2011/10/10)
-
- Deoxyfluorination of phenols
-
An operationally simple ipso fluorination of phenols with a new deoxyfluorination reagent is presented.
- Tang, Pingping,Wang, Weike,Ritter, Tobias
-
supporting information; experimental part
p. 11482 - 11484
(2011/10/02)
-
- 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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- Microwave-accelerated fluorodenitrations and nitrodehalogenations: expeditious routes to labeled PET ligands and fluoropharmaceuticals
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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.
- LaBeaume, Paul,Placzek, Michael,Daniels, Mathew,Kendrick, Ian,Ng, Patrick,McNeel, Melissa,Afroze, Roushan,Alexander, Abigail,Thomas, Rhiannon,Kallmerten, Amy E.,Jones, Graham B.
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body text
p. 1906 - 1909
(2010/09/07)
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- The ionic liquid [bmim]Br as an alternative medium for the catalytic cleavage of aromatic C-F and C-Cl bonds
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The potential of [bmim]Br as an alternative to aprotic dipolar solvents in nickel-catalyzed hydrodehalogenation reactions is demonstrated. Hydrodechlorination of pentafluorochlorobenzene proceeds under the action of zinc in aqueous [bmim]Br. Under the above conditions aromatic C-F bonds also undergo slow cleavage. The reaction is significantly accelerated in the presence of nickel complexes with 2,2′-bipyridine or 1,10-phenanthroline. In the case of pentafluoroacetanilide highly regioselective ortho-hydrodefluorination leading to the formation of 3,4,5-trifluoroacetanilide is observed.
- Prikhod'ko, Sergey A.,Adonin, Nicolay Yu.,Parmon, Valentin N.
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scheme or table
p. 2265 - 2268
(2010/05/18)
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- Process for the Synthesis of Highly Active Binary Metal Fluoride as a Fluorinating Agent for Aromatics
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The subject invention relates to a process for the synthesis of highly active binary metal fluoride system for the fluorination of aromatic compounds. Fluorinated aromatic compounds are valuable synthons for the chemical synthesis of pharmaceutical drugs and novel polymers. Fluorobenzene is used to control carbon content in steel manufacturing, is an intermediate for pharmaceuticals, pesticides and other organic compounds. Fluorobenzene is typically produced by the reaction of aniline and sodium nitrite in the presence of hydrogen fluoride. The present invention relates to a process for the synthesis of highly active binary metal fluoride system consists of copper (II) fluoride and aluminum (III) fluoride for the fluorination of aromatic compounds in gas phase and recycling of the reagent, in situ, using O2 and HF.
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Page/Page column 6-7
(2010/02/17)
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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 ORGANIC COMPOUNDS
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Methods for fluorinating organic compounds are described herein.
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Page/Page column 63; 91
(2010/07/10)
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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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- Fluorodecarboxylation, rearrangement and cyclisation: the influence of structure and environment on the reactions of carboxylic acids with xenon difluoride
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The reactions of structurally diverse carboxylic acids with XeF2 in both CH2Cl2/Pyrex and CH2Cl2/PTFE have been studied. Pyrex appears to be a very effective heterogeneous catalyst for an electrophilic mode of reaction of polarised XeF2, leading to rearrangement, cyclisation and cationic products. In CH2Cl2/PTFE, fluorodecarboxylation is the main mode of reaction, in accordance with previous studies, and may occur via a SET reaction of unpolarised XeF2.
- Ramsden, Christopher A.,Shaw, Maxine M.
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body text
p. 3321 - 3324
(2009/08/09)
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- Highly reactive and regenerable fluorinating agent for oxidative fluorination of aromatics
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A newly synthesized copper aluminum fluoride of nominal composition CuAl2F8 exhibits excellent reactivity towards direct oxidative fluorination of aromatic compounds, as well as fluorodechlorination of chloroaromatics. The spent CuAl2F8 reagent can be regenerated by treatment with O2 and HF, and the fluorination process has been demonstrated to retain high conversions through 20 reaction cycles. The main advantages of this new process are safety, minimal waste, and potentially low cost.
- Janmanchi, Krishna Murthy,Dolbier Jr., William R.
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p. 349 - 354
(2013/01/03)
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- The binding energy of Ar to p-difluorobenzene - Ar. How large are three-body effects in p-difluorobenzene - Ar2?
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The technique of velocity map imaging has been used to determine the dissociation energy for the process p-difluorobenzene-Ar2 → p-difluorobenzene-Ar + Ar. The aim of the experiment was to obtain a value for comparison with the dissociation energy for the process p-difluorobenzene-Ar → p-difluorobenzene + Ar in order to ascertain the extent of three-body effects. We find that the dissociation energy for the loss of an Ar atom from p-difluorobenzene-Ar2 is 339 ± 3 cm-1, which is the same within experimental uncertainty as that for the loss of Ar from p-difluorobenzene-Ar (337 ± 4 cm-1). We conclude that the presence of the first Ar affects the binding energy of the second by ～2% or less.
- Bellm, Susan M.,Lawrence, Warren D.
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p. 542 - 546
(2008/10/08)
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- Ring fluorination of non-activated aromatic compounds
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Unsubstituted aromatic compounds and aromatic compounds having one or more electron-withdrawing substituents are fluorinated, preferably in a nitromethane solvent, by contact with tri(halo- or trifluoromethyl) substituted N-fluorotriazinium salts of the following Formula I: wherein three A moieties are independently CR, where each R is independently halogen or trifluoromethyl; two A moieties are independently Z, where each Z is independently nitrogen or a quaternary nitrogen atom and Y is a counterion or group of counterions which are inert to chemical attack by fluorine. Preferably the cation of the salt is 2,4,6-trichloro-1,3,5-triazinium.
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- Electrophilic fluorination
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N-fluorotriazinium salts, especially those of the following Formula I, are electrophilic fluorinating agents useful in fluorinating, preferably in a nitromethane solvent, carbanionic species and/or activated aromatic compounds:wherein three A moieties are independently CR, where each R is, independently, hydrogen, halogen, (primary, secondary or tertiary) amino, hydroxyl, amino, cyano, perfluorothio hydroxysulphonyl, halosulphonyl, hydrocarbyloxysulphonyl,, or a carbon-containing substituent selected from optionally substituted hydrocarbyl, hydrocarbyloxy, hydrocarbyloxycarbonyl, and hydrocarbylthio groups; two A moieties are independently Z, where each Z is independently nitrogen or a quaternary nitrogen atom and Y is a counterion or group of counterions which are inert to chemical attack by fluorine, and oligomers or polymers thereof in which adjacent triazinium moieties are linked by a common R substituent. Preferably the cation of the salt is 2,4,6-trichloro-1,3,5-triazinium.
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- A product analytical study of the thermal and photolytic decomposition of some arenediazonium salts in solution
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Products of thermal and photochemical reactions of eleven arenediazonium tetrafluoroborates in various solvents have been analyzed. All compounds in most solvents undergo unimolecular heterolysis to give singlet aryl cations which are captured by solvent. This mechanism is dominant for arenediazonium ions without electron-withdrawing substituents in all solvents, and the only reaction observed in water. Additionally, appreciable yields of fluoroarenes are obtained by fluoride abstraction by the aryl cation from fluorinated solvents and from tetrafluoroborate in fluorinated solvents. Yields from photochemical processes are very similar to those from thermal reactions indicating that the main reactions proceed through common or very similar intermediates. Aryl cations formed from ion-paired diazonium ions may react with the counterion, but fragmentation of dissociated diazonium ions leads only to solvent-derived product. Some arenediazonium ions in some solvents undergo an alternative radical reaction leading principally to hydrodediazoniation. It is proposed that this reaction involves initial rate-limiting electron transfer from ethanol to the arenediazonium ion followed rapidly by homolysis of the resultant aryldiazenyl radical. Within the same solvent cage, the aryl radical then either abstracts an α-hydrogen from the ethanol radical cation generated in the first step to give the reduction product and protonated acetaldehyde, or combines with it at the oxygen to give a protonated aryl ethyl ether.
- Canning, Peter S. J.,Maskill, Howard,McCrudden, Katharine,Sexton, Brian
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p. 789 - 800
(2007/10/03)
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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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- Process for the preparation of halogenated derivatives and Lewis acid base catalysts thereof
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A process for the preparation of halide compounds, preferably aryl halides, by contacting a gaseous mixture of hydrohalic acid and a compound selected from an aryl halogen formate, an aryl carbonate and equivalents thereof with a Lewis acid catalyst.
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- Preparation process of fluorine substituted aromatic compound
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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.
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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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- Trifluoromethanesulfonic acid: A novel solvent for the electrophilic fluorination of fluoroaromatics
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Trifluoromethanesulfonic acid has been discovered to be an excellent new solvent for promoting the direct elemental fluorination of aromatics. Fluorobenzene has been successfully fluorinated to a mixture of 1,4-difluorobenzene (31%) and 1,2-difluorobenzene (7%) in CFCl3-CF3SO3H (5%), but no further improvement is observed by the addition of boron trifluoride. When the reaction is carried out in only CFCl3, the main reaction pathway is the 1,2- and 1,4-addition of fluorine to fluorobenzene forming cyclohexenes of molecular formula C6H5F5, and only a small amount of 1,4-difluorobenzene is produced. Although both 1,2- and 1,3-difluorobenzene are fluorinated to 1,2,4-trifluorobenzene in CFCl3-CF3SO3H (10%), 1,4-difluorobenzene does not undergo the same electrophilic substitution reaction.
- Coe, Paul L.,Stuart, Alison M.,Moody, David J.
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p. 1807 - 1811
(2007/10/03)
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