- A Convenient and Stable Heterogeneous Nickel Catalyst for Hydrodehalogenation of Aryl Halides Using Molecular Hydrogen
-
Hydrodehalogenation is an effective strategy for transforming persistent and potentially toxic organohalides into their more benign congeners. Common methods utilize Pd/C or Raney-nickel as catalysts, which are either expensive or have safety concerns. In this study, a nickel-based catalyst supported on titania (Ni-phen@TiO2-800) is used as a safe alternative to pyrophoric Raney-nickel. The catalyst is prepared in a straightforward fashion by deposition of nickel(II)/1,10-phenanthroline on titania, followed by pyrolysis. The catalytic material, which was characterized by SEM, TEM, XRD, and XPS, consists of nickel nanoparticles covered with N-doped carbon layers. By using design of experiments (DoE), this nanostructured catalyst is found to be proficient for the facile and selective hydrodehalogenation of a diverse range of substrates bearing C?I, C?Br, or C?Cl bonds (>30 examples). The practicality of this catalyst system is demonstrated by the dehalogenation of environmentally hazardous and polyhalogenated substrates atrazine, tetrabromobisphenol A, tetrachlorobenzene, and a polybrominated diphenyl ether (PBDE).
- Anwar, Muhammad,Beller, Matthias,Dastgir, Sarim,Junge, Kathrin,Leonard, David K.,Ryabchuk, Pavel
-
-
- 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)
-
- 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)
-
- Efficient synthesis method of meta-fluoranisole (by machine translation)
-
The method is characterized by comprising the following steps: taking m-chloronitrobenzene as a raw material, carrying out high-temperature chlorination reaction, nitration reaction and fluorination reaction to obtain 2,4 - 2,4 -difluorobenzene and carrying out a methoxylation reaction with m-difluorobenzene as a raw material and carrying out methoxylation reaction to obtain m-fluorobenzyl ether; and the hydrogenation catalyst is a porous alumina loaded NiO-Co222O3-MoOO3 composite catalyst. The method disclosed by the invention is simple in process and high in product yield. (by machine translation)
- -
-
Paragraph 0026; 0035; 0036; 0045; 0046; 0055; 0056; 0065
(2020/06/05)
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- Hypervalent Iodine(III)-Catalyzed Balz–Schiemann Fluorination under Mild Conditions
-
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
-
p. 9896 - 9900
(2018/07/31)
-
- Reactions of Arylsulfonate Electrophiles with NMe4F: Mechanistic Insight, Reactivity, and Scope
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This paper describes a detailed study of the deoxyfluorination of aryl fluorosulfonates with tetramethylammonium fluoride (NMe4F) and ultimately identifies other sulfonate electrophiles that participate in this transformation. 19F NMR spectroscopic monitoring of the deoxyfluorination of aryl fluorosulfonates revealed the rapid formation of diaryl sulfates under the reaction conditions. These intermediates can proceed to fluorinated products; however, diaryl sulfate derivatives bearing electron-donating substituents react very slowly with NMe4F. Based on these findings, aryl triflate and aryl nonaflate derivatives were explored, since these cannot react to form diaryl sulfates. Aryl triflates were found to be particularly effective electrophiles for deoxyfluorination with NMe4F, and certain derivatives (i.e., those bearing electron-neutral/donating substituents) afforded higher yields than their aryl fluorosulfonate counterparts. Computational studies implicate a similar mechanism for deoxyfluorination of all the sulfonate electrophiles.
- Schimler, Sydonie D.,Froese, Robert D. J.,Bland, Douglas C.,Sanford, Melanie S.
-
p. 11178 - 11190
(2018/09/12)
-
- Application of trivalent iodine compounds as catalysts in Bal-Schiemann reaction
-
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.
- -
-
Paragraph 0152; 0158
(2018/10/19)
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- Transition metal free, late-stage, regiospecific, aromatic fluorination on a preparative scale using a KF/crypt-222 complex
-
We herein report the development of a convenient, regioselective, aromatic fluorination method of hypervalent iodonium ylides for synthesising fluoro-arenes on a preparative scale. This transition metal free, nucleophilic methodology provides good yields for sterically hindered substrates, irrespective of activation. The methodology simplifies reference synthesis for PET imaging.
- Jakobsson, Jimmy Erik,Riss, Patrick Johannes
-
p. 21288 - 21291
(2018/06/26)
-
- METHOD FOR AROMATIC FLUORINATION
-
Disclosed is a fluorination method comprising providing an aryl fluorosuifonate and a fluorinating reagent to a reaction mixture; and reacting the aryl fluorosuifonate and the fluorinating reagent to provide a fluorinated aryl species. Also disclosed is a fluorination method comprising providing, a salt comprising a cation and an aryloxyiate, and SO2F2 to a reaction mixture; reacting the SO2F2 and the ammonium salt to provide a fluorinated aryl species. Further disclosed a fluorination method comprising providing a compound having the structure Ar-OH to a reaction mixture; where A is an aryl or heteroaryl; providing SO2F2 to the reaction mixture; providing a fluorinating reagent to the reaction mixture; reacting the SO2F2, the fluorinating reagent and the compound having the structure Ar-OH to provide a fluorinated aryl species having the structure Ar-F.
- -
-
Paragraph 0047-0049
(2017/12/18)
-
- Nucleophilic deoxyfluorination of phenols via aryl fluorosulfonate intermediates
-
This report describes a method for the deoxyfluorination of phenols with sulfuryl fluoride (SO2F2) and tetramethylammonium fluoride (NMe4F) via aryl fluorosulfonate (ArOFs) intermediates. We first demonstrate that the reaction of ArOFs with NMe4F proceeds under mild conditions (often at room temperature) to afford a broad range of electronically diverse and functional group-rich aryl fluoride products. This transformation was then translated to a one-pot conversion of phenols to aryl fluorides using the combination of SO2F2 and NMe4F. Ab initio calculations suggest that carbon-fluorine bond formation proceeds via a concerted transition state rather than a discrete Meisenheimer intermediate.
- Schimler, Sydonie D.,Cismesia, Megan A.,Hanley, Patrick S.,Froese, Robert D.J.,Jansma, Matthew J.,Bland, Douglas C.,Sanford, Melanie S.
-
p. 1452 - 1455
(2017/02/10)
-
- 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)
-
- Preparation method of m-fluoroanisole
-
The invention discloses a preparation method of m-fluoroanisole. The preparation method includes following steps: (1), adding methanol into a reaction kettle, heating to 20-60 DEG C, adding potassium hydroxide, and holding temperature; (2), continuing to add dimethyl sulfoxide and cuprous chloride into the reaction kettle, heating, and adding m-difluorobenzene for reaction for 14-18 h; (3), adding water into a reaction product, distilling to obtain a crude product, further rectifying to obtain m-fluoroanisole. The preparation method is easy-to-get and cheap in raw materials, few in steps, simple to operate and needless of high-pressure equipment, raw material cost and production cost are lowered greatly, product yield can reach higher than 80%, which is far higher than that of existing processes, and the preparation method is suitable for large-scale production.
- -
-
Paragraph 0016
(2017/07/21)
-
- RADIOIODINATED COMPOUNDS
-
This disclosure relates to reagents and methods useful in the synthesis of aryl iodines, for example, in the preparation of iodine labeled radiotracers. The reagents and methods provided herein may be used to access a broad range of compounds, including aromatic compounds, heteroaromatic compounds, amino acids, nucleotides, and synthetic compounds.
- -
-
Page/Page column 49
(2015/12/08)
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- A Fluorinated Ligand Enables Room-Temperature and Regioselective Pd-Catalyzed Fluorination of Aryl Triflates and Bromides
-
A new biaryl monophosphine ligand (AlPhos, L1) allows for the room-temperature Pd-catalyzed fluorination of a variety of activated (hetero)aryl triflates. Furthermore, aryl triflates and bromides that are prone to give mixtures of regioisomeric aryl fluorides with Pd-catalysis can now be converted to the desired aryl fluorides with high regioselectivity. Analysis of the solid-state structures of several Pd(II) complexes, as well as density functional theory (DFT) calculations, shed light on the origin of the enhanced reactivity observed with L1.
- Sather, Aaron C.,Lee, Hong Geun,De La Rosa, Valentina Y.,Yang, Yang,Müller, Peter,Buchwald, Stephen L.
-
supporting information
p. 13433 - 13438
(2015/11/09)
-
- Studying regioisomer formation in the pd-catalyzed fluorination of aryl triflates by deuterium labeling
-
Isotopic labeling has been used to determine that a portion of the desired product in the Pd-catalyzed fluorination of electron-rich, non-ortho-substituted aryl triflates results from direct C-F cross-coupling. In some cases, formation of a Pd-aryne intermediate is responsible for producing undesired regioisomers. The generation of the Pd-aryne intermediate occurs primarily via ortho-deprotonation of a L·Pd(Ar)OTf (L = biaryl monophosphine) species by CsF and thus competes directly with the transmetalation step of the catalytic cycle. Deuterium labeling studies were conducted with a variety of aryl triflates.
- Milner, Phillip J.,Kinzel, Tom,Zhang, Yong,Buchwald, Stephen L.
-
supporting information
p. 15757 - 15766
(2015/02/02)
-
- 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)
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- 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)
-
- Synthesis of functionalized aryl fluorides using organolithium reagents in flow microreactors
-
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
-
supporting information
p. 705 - 708
(2013/05/08)
-
- 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)
-
- Evidence for in situ catalyst modification during the Pd-catalyzed conversion of aryl triflates to aryl fluorides
-
A mechanistic investigation of the Pd-catalyzed conversion of aryl triflates to fluorides is presented. Studies reveal that C-F reductive elimination from a LPdII(aryl)F complex (L = t-BuBrettPhos or RockPhos) does not occur when the aryl group is electron rich. Evidence is presented that a modified phosphine, generated in situ, serves as the actual supporting ligand during catalysis with such substrates. A preliminary study of the reactivity of a LPdII(aryl)F complex based on this modified ligand is reported.
- Maimone, Thomas J.,Milner, Phillip J.,Kinzel, Tom,Zhang, Yong,Takase, Michael K.,Buchwald, Stephen L.
-
supporting information; experimental part
p. 18106 - 18109
(2012/01/02)
-
- Unprecedented directing group ability of cyclophanes in arene fluorinations with diaryliodonium salts
-
For the first time it is shown that exceptionally electron-rich arene rings can be fluorinated exclusively during the reductive elimination reactions of diaryliodonium fluorides. The 5-methoxy[2.2]paracyclophan-4-yl directing group simultaneously reduces unproductive aryne chemistry and eliminates ligand exchange reactions by a combination of steric and electronic effects. Use of the cyclophane directing group permits an unprecedented degree of control in fluorination reactions of diaryliodonium salts.
- Graskemper, Joseph W.,Wang, Bijia,Qin, Linlin,Neumann, Kiel D.,Dimagno, Stephen G.
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p. 3158 - 3161
(2011/08/06)
-
- Iodonium Cyclophanes for SECURE Arene Functionalization
-
This disclosure relates to compounds, reagents, and methods useful in the synthesis of aryl fluorides, for example, in the preparation of 18F labeled radiotracers. For example, this disclosure provides universal “locked” aryl substituents that result in StereoElectronic Control of Unidirectional Reductive Elimination (SECURE) from diaryliodonium salts. The reagents and methods provided herein may be used to access a broad range of compounds, including aromatic compounds, heteroaromatic compounds, amino acids, nucleotides, and synthetic compounds.
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Page/Page column 27-28
(2011/08/08)
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- A single phosphine ligand allows palladium-catalyzed intermolecular C-O bond formation with secondary and primary alcohols
-
Forging a bond: An efficient, general palladium catalyst for C-O bond-forming reactions of secondary and primary alcohols with a range of aryl halides has been developed using the ligand 1. Heteroaryl halides, and for the first time, electron-rich aryl halides can be coupled with secondary alcohols. A diverse set of substrate combinations are possible with just a single ligand, thus obviating the need to survey multiple ligands. Copyright
- Wu, Xiaoxing,Fors, Brett P.,Buchwald, Stephen L.
-
supporting information; experimental part
p. 9943 - 9947
(2011/12/05)
-
- 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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- Synthesis of aryl fluorides on a solid support and in solution by utilizing a fluorinated solvent
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(Figure Presented) F for fast: The perfluorinated solvent C 6F14 is the key to a new variant of the BalzSchiemann reaction for the synthesis of fluorinated arenes. Triazenes are converted into fluoroarenes under mild con-ditions on a support and in solution (see scheme). The method is straightforward and inexpensive, and yields previously difficult-to-prepare fluoroarenes in high purity.
- Doebele, Marion,Vanderheiden, Sylvia,Jung, Nicole,Braese, Stefan
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supporting information; experimental part
p. 5986 - 5988
(2010/10/01)
-
- Rh(I)-catalyzed decarboxylative transformations of arenecarboxylic acids: Ligand- and reagent-controlled selectivity toward hydrodecarboxylation or heck-mizoroki products
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(Chemical Equetion Presentation) A Rh(I)-based catalyst system has been developed to promote three types of decarboxylative transformations of arenecarboxylic acids: (1) hydrodecarboxylation, (2) Heck-Mizoroki olefination, and (3) conjugate addition. Scopes of reactions (1) and (2) were studied, and the ligand and reagent dependence of selectivity was explored.
- Sun, Zhong-Ming,Zhang, Jing,Zhao, Pinjing
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supporting information; experimental part
p. 992 - 995
(2010/06/16)
-
- Formation of arf from lpdar(f): catalytic conversion of aryl triflates to aryl fluorides
-
Despite increasing pharmaceutical importance, fluorinated aromatic organic molecules remain difficult to synthesize. Present methods require either harsh reaction conditions or highly specialized reagents, making the preparation of complex fluoroarenes ch
- Watson, Donald A.,Su, Mingjuan,Teverovskiy, Georgiy,Zhang, Yong,Garcia-Fortanet, Jorge,Kinzel, Tom,Buchwaldf, Stephen L.
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scheme or table
p. 1661 - 1664
(2010/06/16)
-
- Synthesis of novel structurally simplified estrogen analogues with electron-donating groups in ring A
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A library of 25 novel estrogen analogues were prepared in five to eight steps from mostly commercially available substituted anisoles via bromination, formylation, Corey-Fuchs reaction, elimination, and Sonogashira reaction. Georg Thieme Verlag Stuttgart.
- Tietze, Lutz F.,Vock, Carsten A.,Krimmelbein, Ilga K.,Nacke, Linda
-
experimental part
p. 2040 - 2060
(2009/12/27)
-
- Hydroxylated nebivolol metabolites
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Hydroxylated nebivolol metabolites increase NO release from human endothelial cell preparations in a concentration dependent fashion following acute administration. In addition, hydroxylated nebivolol metabolites, including but not limited to 4-hydroxy-6,6′difluoro-, 4-hydroxy-5-phenol-6,6′difluoro-, and 4-hydroxy-8-pheno-6,6′difluoro-, have the ability to increase the capacity for NO release in human endothelial cells following chronic administration. This invention provides hydroxylated nebivolol metabolites and compositions comprising nebivolol and/or at least one hydroxylated metabolite of nebivolol and/or at least one additional compound used to treat cardiovascular diseases or a pharmaceutically acceptable salt thereof. In addition, this invention provides methods of treating and/or preventing vascular diseases by administering at least one hydroxylated metabolite of nebivolol that is capable of releasing a therapeutically effective amount of nitric oxide to a targeted site affected by the vascular disease. Also, this invention is directed to the treatment and/or prevention of migraine headaches administering at least one hydroxylated metabolite of nebivolol. This invention may also be used in conjunction with or as a single treatment of metabolic syndrome disorders.
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- Novel synthesis of desymmetrized resorcinol derivatives: Aryl fluoride displacement on deactivated substrates
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A short, high-yielding synthesis of differentially substituted resorcinol derivatives has been developed that utilizes 1,3-difluorobenzene as the starting material and employs sequential nucleophilic aromatic substitution (S NAr) reactions to generate desymmetrized products. The scope and limitations of the second SNAr reaction on the deactivated 1-alkoxy-3-fluorobenzene intermediates have been investigated. This methodology has also been employed in the synthesis of desymmetrized catechol derivatives from 1,2-difluorobenzene.
- Kim, Aujin,Powers, Jeremiah D.,Toczko, Jennifer F.
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p. 2170 - 2172
(2007/10/03)
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- Tin(IV) chloride-chiral pyrogallol derivatives as new Lewis acid-assisted chiral Bronsted acids for enantioselective polyene cyclization
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(Matrix Presented) New Lewis acid-assisted Bronsted acids (LBAs), tin(IV) chloride-2,6-dialkoxyphenols, serve as artificial cyclases for biomimetic polyene cyclization. For example, the enantioselective cyclization of 4-(homogeranyl)toluene using tin(IV) chloride-2,6-di[(1′R,2′R)- trans-2′-(3″,5″-xylyl)cyclohexanoxy]-phenol gave a trans-fused tricyclic compound with 85% ee.
- Kumazawa, Keiko,Ishihara, Kazuaki,Yamamoto, Hisashi
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p. 2551 - 2554
(2007/10/03)
-
- 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
-
p. 789 - 800
(2007/10/03)
-
- 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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-
- Arene complexes of transition metals in reactions with nucleophilic reagents. XXIX. Poly[(p-cyclopentadienylmethylstyrene)rhodium]2+ as catalyst of alkoxydefluorination of fluoroarenes
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The poly[(p-cyclopentadienylmethylstyrene)rhodium]2+ produced in situ by treating the respective dichloride complex with silver triflate in the presence of primary alcohols (methanol, propanol, hexanol) was used as catalyst grafted on polymeric sublayer for alkoxydefluorination of fluoroarenes. The activity of the catalyst in alcoholysis of fluorobenzene and p-fluorotolyene is similar to that of the corresponding homogeneous catalysts. The catalyst conserves its activity for repeated application.
- Goryunov,Steingarts
-
p. 246 - 251
(2007/10/03)
-
- An unexpected route to fluorinated anisoles
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We found a new one-pot procedure for the synthesis of polyfluoroanisoles from polyfluoroanilines. The reaction involves aromatic nucleophilic substitution of o- or p-fluorine of benzenediazonium salt with methoxy group followed by reductive removal of the diazonium group.
- Takechi, Naoto,Fukai, Yasushi,Oka, Kazuyoshi,Huisgen, Rolf
-
-
- Facile preparation of aromatic fluorides by deaminative fluorination of aminoarenes using hydrogen fluoride combined with bases
-
One-pot deaminative fluorination of aminoarenes including heteroaromatics, namely, diazotization of aminoarenes followed by in situ fluoro-dediazoniation of the corresponding diazonium ions, was successfully accomplished to produce fluoroarenes in high yields by using hydrogen fluoride combined with base solutions. The diazotization stage has been found to play the most important part in yielding fluoroarenes effectively. It was greatly influenced by the composition of the HF solution and enhanced by employing appropriate amounts of bases such as pyridine under carefully controlled conditions. The fluoro-dediazoniation stage was effectively accelerated photochemically to afford fluoroarenes having polar substituents such as hydroxyl, nitro and so on in high yields.
- Yoneda,Fukuhara
-
-
- Aryl fluoride syntheses involving reactions of aryllead triacetates with boron trifluoride-diethyl ether complex
-
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)
-
- Evidence for Charge Localisation by Strong Hydrogen Bonding in Fluoride-Phenol Complexes and its Effects on Reactivity/Selectivity
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Measurements of yields and rates of methylation of substituted phenols, and correlations for the prediction of MeI labelling conditions, show evidence for charge localisation in fluoride-phenol strong hydrogen-bonded complexes and its effects on selectivity/reactivity.
- Cork, David G.,Hayashi, Nobuyoshi
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p. 527 - 529
(2007/10/02)
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- Correlation of Reaction Rates with a Substituent Constant Scale Derived from Calculated Electron Densities for a Computer Control Algorithm
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A new ? substituent scale based on electron density calculations by the AM1 quantum mechanical model has been established and used to correlate rates of O-methylation of substituted phenols, as part of a chemical artificial intelligence to control a fully automated apparatus for methyl iodide labeling.
- Cork, David G.,Hayashi, Nobuyoshi
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p. 1583 - 1585
(2007/10/02)
-
- A new synthesis of aryl fluorides: The reaction of caesium fluoroxysulfate with arylboronic acids and derivatives
-
The ipso fluorination of arylboronic acids and some derivatives with caesium fluoroxysulfate has been developed. The reaction proceeds with the wide range of functionalised aromatics and is strongly solvent dependent.
- Diorazio,Widdowson,Clough
-
p. 8073 - 8088
(2007/10/02)
-
- A Facile Preparation of Aryl Triflates. Decomposition of Arenediazonium Tetrafluoroborate Salts in Trifluoromethanesulfonic Acid
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The thermal or photochemical decomposition of arenediazonium tetrafluoroborate salts n trifluoromethanesulfonic acid, with or without organic bases such as pyridine, provides aryl triflates in high yields.
- Yoneda, Norihiko,Fukuhara, Tsuyoshi,Mizokami, Takao,Suzuki, Akira
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p. 459 - 460
(2007/10/02)
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- PREPARATION OF AROMATIC FLUORIDES VIA DIAZOTIZATION AND PHOTOCHEMICALLY INDUCED FLUORO-DEDIAZONIATION OF AROMATIC AMINES IN ANHYDROUS HYDROGEN FLUORIDE - ORGANIC BASE SOLUTIONS
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Fluoro-dediazoniation of aromatic diazonium ions, produced by the diazotization of the corresponding aromatic amines with NaNO2 in anhydrous hydrogen fluorides (AHF) - organic base solutions, was accelerated photochemically to afford Ar-F efficiently in AHF - organic base solutions in situ.
- Yoneda, Norihiko,Fukuhara, Tsuyoshi,Kikuchi, Tetsuo,Suzuki, Akira
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p. 865 - 872
(2007/10/02)
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- DIRECT FLUORINATION OF PHENOL AND CRESOLS
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A study has been made of the reaction of phenol with elemental fluorine using a variety of solvents and reaction temperatures.Yields of o- and p-fluorophenol were obtained as high as 85percent.The isomer ratio changed drastically between phenol conversions of 10percent and 56percent.The o-isomer changed to unidentified polymeric substances at higher conversion, but it might also be assumed that interconversion of some isomers is occuring.The three cresols have also been succesfully fluorinated with elemental fluorine. p-Cresol gave some expected 2-fluoroderivative but also formed a fluorocyclohexadienyl ketone.
- Misaki, Susumu
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p. 159 - 172
(2007/10/02)
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- Substrate Selectivity and Orientation in Aromatic Substitution by Molecular Fluorine
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Direct elemental fluorination of representative aromatic substrates, including PhH, PhCH3, PhF, PhCl, PhBr, PhNO2, PhCN, and PhOCH3, has been investigated in inert solvents, e.g., CCl3F and other fluorocarbons, over the temperature range -154 to 40 deg C.In order to achieve the necessary control of the extremely reactivve electrophile, and to minimize unwanted modifications of the reaction environment, the fluorination has been carried out at extremely low rate and correspondingly low conversions, generally below 0.01percent, using as a reagent gaseous mixtures of F2 highly diluted (+ constants for all the substituents investigated, giving a ρ+ value of -2.45 for aromatic substitution by elemental fluorine with a correlation coefficient of 0.993.These results characterize F2 as a highly reactive, and correspondently unselective, reagent, and support a polar electrophilic substitution mechanism that is discussed and compared with other plausible fluorination pathways.
- Cacace, F.,Giacomello, P.,Wolf, A. P.
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p. 3511 - 3515
(2007/10/02)
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