- MILD CONVERSION OF PRIMARY ALCOHOLS AND ALDEHYDES TO ACID FLUORIDES WITH CAESIUM FLUOROXYSULPHATE
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Caesium fluoroxysulphate in acetonitrile medium at 35 deg C converts primary alcohols and alkyl, as well as aryl aldehydes, to acid fluorides in high yield.
- Stavber, Stojan,Planinsek, Zdenka,Zupan, Marko
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- Perfluoroalkyl Cobalt(III) Fluoride and Bis(perfluoroalkyl) Complexes: Catalytic Fluorination and Selective Difluorocarbene Formation
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Four perfluoroalkyl cobalt(III) fluoride complexes have been synthesized and characterized by elemental analysis, multinuclear NMR spectroscopy, X-ray crystallography, and powder X-ray diffraction. The remarkable cobalt fluoride 19F NMR chemical shifts (-716 to -759 ppm) were studied computationally, and the contributing paramagnetic and diamagnetic factors were extracted. Additionally, the complexes were shown to be active in the catalytic fluorination of p-toluoyl chloride. Furthermore, two examples of cobalt(III) bis(perfluoroalkyl)complexes were synthesized and their reactivity studied. Interestingly, abstraction of a fluoride ion from these complexes led to selective formation of cobalt difluorocarbene complexes derived from the trifluoromethyl ligand. These electrophilic difluorocarbenes were shown to undergo insertion into the remaining perfluoroalkyl fragment, demonstrating the elongation of a perfluoroalkyl chain arising from a difluorocarbene insertion on a cobalt metal center. The reactions of both the fluoride and bis(perfluoroalkyl) complexes provide insight into the potential catalytic applications of these model systems to form small fluorinated molecules as well as fluoropolymers.
- Leclerc, Matthew C.,Bayne, Julia M.,Lee, Graham M.,Gorelsky, Serge I.,Vasiliu, Monica,Korobkov, Ilia,Harrison, Daniel J.,Dixon, David A.,Baker, R. Tom
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- Fluoride complexes of cyclometalated iridium(III)
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Many electroluminescent devices rely on cyclometalated iridium(III). Their advancement depends on access to reactive starting materials because of the inertness of Ir(III). Notably, fluoride complexes of bis(cyclometalated) Ir(III) are scarce. Syntheses of bridged and terminal fluorides are reported here. New compounds are luminescent and thermally reactive; they are characterized by ground-state and optical methods. Crystal structures were determined for one bridging and one terminal fluoride complex. The terminal fluoride shows intramolecular hydrogen bonding to an adjacent 3,5-dimethylpyrazole ligand; a lesser interaction may occur between F and a nearby aromatic C-H bond. Terminal fluoride complexes react with carbon-, silicon-, and sulfur-based electrophiles. The new complexes phosphoresce with microsecond lifetimes at 77 and 298 K. Density-functional theory calculations indicate triplet states with little contribution from fluoride. The compounds herein are versatile phosphors having the ground-state reactivity of late transition metal fluorides.
- Maity, Ayan,Stanek, Robert J.,Anderson, Bryce L.,Zeller, Matthias,Hunter, Allen D.,Moore, Curtis E.,Rheingold, Arnold L.,Gray, Thomas G.
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- Metal-free approach for hindered amide-bond formation with hypervalent iodine(iii) reagents: application to hindered peptide synthesis
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A new bio-inspired approach is reported for amide and peptide synthesis using α-amino esters that possess a potential activating group (PAG) at the ester residue. To activate the ester functionality under mild metal-free conditions, we exploited the facile dearomatization of phenols with hypervalent iodine(iii) reagents. Using a pyridine-hydrogen fluoride complex, highly reactive acyl fluoride intermediates can be successfully generated, thereby allowing for the smooth formation of sterically hindered amides and peptides from bulky amines and α-amino esters, respectively.
- Lee, Hyo-Jun,Huang, Xiao,Sakaki, Shigeyoshi,Maruoka, Keiji
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supporting information
p. 848 - 855
(2021/02/09)
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- Acyl fluorides from carboxylic acids, aldehydes, or alcohols under oxidative fluorination
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We describe a novel reagent system to obtain acyl fluorides directly from three different functional group precursors: carboxylic acids, aldehydes, or alcohols. The transformation is achieved via a combination of trichloroisocyanuric acid and cesium fluoride, which facilitates the synthesis of various acyl fluorides in high yield (up to 99%). It can be applied to the late-stage functionalization of natural products and drug molecules that contain a carboxylic acid, an aldehyde, or an alcohol group.
- Liang, Yumeng,Zhao, Zhengyu,Taya, Akihito,Shibata, Norio
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supporting information
p. 847 - 852
(2021/02/06)
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- Carboxylic Acid Deoxyfluorination and One-Pot Amide Bond Formation Using Pentafluoropyridine (PFP)
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This work describes the application of pentafluoropyridine (PFP), a cheap commercially available reagent, in the deoxyfluorination of carboxylic acids to acyl fluorides. The acyl fluorides can be formed from a range of acids under mild conditions. We also demonstrate that PFP can be utilized in a one-pot amide bond formation via in situ generation of acyl fluorides. This one-pot deoxyfluorination amide bond-forming reaction gives ready access to amides in yields of ≤94%.
- Brittain, William D. G.,Cobb, Steven L.
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supporting information
p. 5793 - 5798
(2021/08/01)
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- Gram-Scale Preparation of Acyl Fluorides and Their Reactions with Hindered Nucleophiles
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A series of acyl fluorides was synthesized at 100 mmol scale using phase-transfer-catalyzed halogen exchange between acyl chlorides and aqueous bifluoride solution. The convenient procedure consists of vigorous stirring of the biphasic mixture at room temperature, followed by extraction and distillation. Isolated acyl fluorides (usually 7-20 g) display excellent purity and can be transformed into sterically hindered amides and esters when treated with lithium amide bases and alkoxides under mild conditions.
- Barbasiewicz, Micha?,Tryniszewski, Micha?
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- Halide-Accelerated Acyl Fluoride Formation Using Sulfuryl Fluoride
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Herein, we report a new one-pot sequential method for SO2F2-mediated nucleophilic acyl substitution reactions starting from carboxylic acids. A mechanistic study revealed that SO2F2-mediated acid activation proceeds via the anhydride, which is then converted to the corresponding acyl fluoride. Tetrabutylammonium chloride or bromide accelerate the formation of acyl fluoride. Optimized halide-accelerated conditions were used to synthesize acyl fluorides in 30-80percent yields, and esters, amides, and thioesters in 72-96percent yields without reoptimization for each nucleophile.
- Foth, Paul J.,Malig, Thomas C.,Yu, Hao,Bolduc, Trevor G.,Hein, Jason E.,Sammis, Glenn M.
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supporting information
p. 6682 - 6686
(2020/09/02)
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- Methoxylation of Acyl Fluorides with Tris(2,4,6-trimethoxyphenyl)phosphine via C-OMe Bond Cleavage under Metal-Free Conditions
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Acyl fluorides are subjected to methoxylation with tris(2,4,6-trimethoxyphenyl)phosphine (TMPP) to afford the corresponding methyl esters in good to excellent yields. This transformation is featured by C(sp2)-OMe bond cleavage under metal-free conditions. Unprecedented utilization of TMPP as a methoxylating agent realized the installation of an OMe group into the desired products.
- Ishida, Takumi,Nishihara, Yasushi,Wang, Xiu,Wang, Zhenhua
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p. 7526 - 7533
(2020/06/27)
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- C-F Bond Activation of a Perfluorinated Ligand Leading to Nucleophilic Fluorination of an Organic Electrophile
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We report a fluorine transfer reaction in which fluorine from a perfluorinated ligand undergoes C-F bond activation and transfers to an electrophile, resulting in the formation of a new fluorinated product and dimerization of the monodefluorinated complex. Treatment of [(η5,κ2C-C5Me4CH2C6F5CH2NC3H2NMe)-RhCl] with the organic electrophile, toluoyl chloride, resulted in the formation of a rhodium(III) metallocycle via C-F bond activation assisted defluorinative coupling. Fission of the C-F bond liberated nucleophilic fluoride, which converted acyl chloride to acyl fluoride. The overall reaction was monitored using a multivariate analysis approach in real time.
- Hanson-Heine, Magnus W. D.,Licence, Peter,Marr, Andrew C.,Morgan, Patrick J.,Saunders, Graham C.,Thomas, Hayden P.
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supporting information
p. 2116 - 2124
(2020/07/23)
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- N-Hydroxybenzimidazole as a structurally modifiable platform forN-oxyl radicals for direct C-H functionalization reactions
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Methods for direct functionalization of C-H bonds mediated byN-oxyl radicals constitute a powerful tool in modern organic synthesis. While severalN-oxyl radicals have been developed to date, the lack of structural diversity for these species has hampered further progress in this field. Here we designed a novel class ofN-oxyl radicals based onN-hydroxybenzimidazole, and applied them to the direct C-H functionalization reactions. The flexibly modifiable features of these structures enabled facile tuning of their catalytic performance. Moreover, with these organoradicals, we have developed a metal-free approach for the synthesis of acyl fluoridesviadirect C-H fluorination of aldehydes under mild conditions.
- Hatanaka, Miho,Jiang, Julong,Maruoka, Keiji,Matsumoto, Akira,Sakamoto, Ryu,Sakurai, Shunya,Tsuzuki, Saori,Yoshii, Tomomi
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p. 5772 - 5778
(2020/06/22)
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- Efficient cleavage of tertiary amide bonds: Via radical-polar crossover using a copper(ii) bromide/Selectfluor hybrid system
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A novel approach for the efficient cleavage of the amide bonds in tertiary amides is reported. Based on the selective radical abstraction of a benzylic hydrogen atom by a CuBr2/Selectfluor hybrid system followed by a selective cleavage of an N-C bond, an acyl fluoride intermediate is formed. This intermediate may then be derivatized in a one-pot fashion. The reaction proceeds under mild conditions and exhibits a broad substrate scope with respect to the tertiary amide moiety as well as to nitrogen, oxygen, and carbon nucleophiles for the subsequent derivatization. Mechanistic studies suggest that the present reaction proceeds via a radical-polar crossover process that involves benzylic carbon radicals generated by the selective radical abstraction of a benzylic hydrogen atom by the CuBr2/Selectfluor hybrid system. Furthermore, a synthetic application of this method for the selective cleavage of peptides is described. This journal is
- Maruoka, Keiji,Matsumoto, Akira,Wang, Zhe
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p. 12323 - 12328
(2020/12/08)
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- METHOD FOR MANUFACTURING DIFLUOROMETHYLENE COMPOUND
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The problem to be solved by the present invention is to provide a novel method for producing a difluoromethylene compound. This problem is solved by a method for producing a difluoromethylene compound containing a —CF2— moiety, the method comprising step A of mixing: a) a carbonyl compound containing a —C(O)— moiety;b) optionally an amine;c) a fluoride represented by the formula: MF, wherein M represents a Group 1 element of the periodic table;d) a halogenated fluorine compound represented by the formula: XFn, wherein X represents chlorine, bromine, or iodine, and n is a natural number of 1 to 5; ande) sulfur chloride.
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Paragraph 0219-0223
(2020/03/28)
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- Nickel-catalyzed decarbonylative stannylation of acyl fluorides under ligand-free conditions
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Nickel-catalyzed decarbonylative stannylation of acyl fluorides under ligand-free conditions was disclosed. A variety of aromatic acyl fluorides are capable of reacting with silylstannanes in the presence of cesium fluoride. A one-pot decarbonylative stannylation/Migita-Kosugi-Stille reaction of benzoyl fluoride, giving rise to the direct formation of the corresponding cross-coupled products, further demonstrated the synthetic utility of the present method. This newly developed methodology with a good functional-group compatibility via C-F bond cleavage and C-Sn bond formation under nickel catalysis opens a new area for the functionalization of acyl fluorides in terms of carbon-heteroatom bond formation.
- Wang, Xiu,Wang, Zhenhua,Liu, Li,Asanuma, Yuya,Nishihara, Yasushi
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- Nickel-catalysed decarbonylative borylation of aroyl fluorides
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The first Ni(cod)2/PPh3 catalyst system has been established for decarbonylative borylation of aroyl fluorides with bis(pinacolato)diboron. A wide range of functional groups in the substrates were well tolerated. The ease of access of the starting aroyl fluorides indicates that these results might become an alternative to the existing decarbonylation events.
- Wang, Zhenhua,Wang, Xiu,Nishihara, Yasushi
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supporting information
p. 13969 - 13972
(2019/01/03)
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- Synthesis of acyl fluorides via photocatalytic fluorination of aldehydic C-H bonds
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Acyl fluorides are versatile acylating agents owing to their unique stability. Their synthesis, however, can present challenges and is typically accomplished through deoxyfluorination of carboxylic acids. Here, we demonstrate that acyl fluorides can be prepared directly from aldehydes via a C(sp2)-H fluorination reaction involving the inexpensive photocatalyst sodium decatungstate and electrophilic fluorinating agent N-fluorobenzenesulfonimide. This convenient fluorination strategy enables direct conversion of aliphatic and aromatic aldehydes into acylating agents.
- Meanwell, Michael,Lehmann, Johannes,Eichenberger, Marc,Martin, Rainer E.,Britton, Robert
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supporting information
p. 9985 - 9988
(2018/09/11)
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- High-throughput evaluation of in situ-generated cobalt(III) catalysts for acyl fluoride synthesis
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Using a high-throughput experimental procedure, a series of cobalt(iii) complexes of the general formula CpRCo(I)(X)(L) were prepared and screened for their activity towards the catalytic nucleophilic fluorination of benzoyl chloride. A highly active catalyst was identified, and successfully employed in a mild and effective protocol for the synthesis of a group of acyl fluoride compounds.
- Lee, Graham M.,Clément, Roxanne,Baker, R. Tom
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p. 4996 - 5003
(2017/11/09)
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- Palladium-catalyzed fluorocarbonylation using N-formylsaccharin as CO source: General access to carboxylic acid derivatives
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N-Formylsaccharin, an easily accessible crystalline compound, has been employed as an efficient CO source in Pd-catalyzed fluorocarbonylation of aryl halides to afford the corresponding acyl fluorides in high yields. The reactions use a near-stoichiometric amount of the CO source (1.2 equiv) and tolerate diverse functional groups. The acyl fluorides obtained could be readily transformed into various carboxylic acid derivatives such as carboxylic acid, esters, thioesters, and amides in a one-pot procedure.
- Ueda, Tsuyoshi,Konishi, Hideyuki,Manabe, Kei
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supporting information
p. 5370 - 5373
(2013/11/06)
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- Enantioselective acylation of silyl ketene acetals through fluoride anion-binding catalysis
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A highly enantioselective acylation of silyl ketene acetals with acyl fluorides has been developed to generate useful α,α-disubstituted butyrolactone products. This transformation is promoted by a new thiourea catalyst and 4-pyrrolidinopyridine and represents the first example of enantioselective thiourea anion-binding catalysis with fluoride.
- Birrell, James A.,Desrosiers, Jean-Nicolas,Jacobsen, Eric N.
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supporting information; experimental part
p. 13872 - 13875
(2011/10/09)
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- Reactions of alcohols with cesium fluoroxysulfate
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The reactions of alcohols with cesium fluoroxysulfate (CsSO4F) in MeCN suspension were studied, and the role of the structure of the alcohol and the reaction conditions on the course of reaction was determined. Secondary benzyl alcohols bearing a nonactivating aromatic ring were selectively oxidized to the corresponding ketones, while the CsSO4F-mediated reaction of phenyl-1-naphthylmethanol resulted in the formation of 1-fluoronaphthalene and benzaldehyde. Cyclic and noncyclic secondary alcohols were readily converted to ketones, as well as 1-hydroxybenzecyclanes to benzocyclanones- 1, without any further fluorination or oxidation under the reaction conditions. On the other hand, reactions of primary alcohols with CsSO4F resulted in the formation of acid fluorides derived from further fluorination of aldehydes. Another type of transformation was observed in the case of alcohols bearing a benzyl functional group attached geminal to a hydroxy group, where decarbanylation of reactive intermediates resulting in the formation of benzyl fluoride derivatives became the main process. 2- Phenylethanol was so converted to benzyl fluoride and phenylacetyl fluoride in a 3:1 relative ratio, while 2-phenyl-1-propanol was selectively transformed to 1-phenyl-1-fluoroethane. The presence of the radical inhibitor nitrobenzene in the reaction mixture considerably inhibited conversion of the starting material. The same effect was observed by lowering the solvent polarity. Hammett correlation analysis of the effect of substituents on the reaction rates of oxidation of a set of substituted 1-phenyl-1-ethanols to acetophenones gave the reaction constant p+ = -0.32, while analysis of analogous data for the transformations of benzyl alcohols to benzoyl fluorides gave the value of -0.54. A mechanism including radical intermediates was proposed for the transformation of alcohols by CsSO4F.
- Stavber, Stojan,Kosir, Iztok,Zupan, Marko
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p. 4916 - 4920
(2007/10/03)
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- Rearrangement and radical mediated decarboxylation of trimethylsilyl benzoates using xenon difluoride
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Treatment of trimethylsilyl benzoates 1 with xenon difluoride in CH2Cl2 or C6F6 results in a novel ester rearrangement and formation of aryl fluoroformates 2: rearrangement is not observed in MeCN solution in wh
- Nongkunsarn, Pakawan,Ramsden, Christopher A.
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p. 121 - 122
(2007/10/03)
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- Die Reacktionen von Bis(perfluoralkyl)cadmium-Komplexen mit Arylcarbonsaeurechloriden: Synthese von Aryl(perfluoralkyl)ketonen, (Perfluoralkyl-dihydropyridin)arylcarbonsaeureamiden, α,α-Bis(trifluormethyl)benzylalkoholen und Benzoesaeure-α,α-bis(trifluormethyl)benzylestern
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Perfluoroalkylcadmium complexes react with aroyl halides in the presence of strong bases such as pyridine to give the corresponding ketones ArCORf (which can be isolated in 5-51percent yield) and (perfluoroalkyldihydropyridine)aroylamides.The pure substances are obtained by chromatography.Aroyl fluorides and α,α-bis(trifluoromethyl)benzyl alcohols and benzoic acid-α,α-bis(trifluoromethyl)benzyl esters can be isolated as by-products.The dependency of the products formed on the kind of bases used as well as the reaction mechanisms are described.All products were identified by their 19F, 1H, 13C NMR, mass and IR spectra, and by elemental analysis.
- Naumann, Dieter,Finke, Martina,Lange, Horst,Dukat, Wolfgang,Tyrra, Wieland
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p. 215 - 237
(2007/10/02)
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- Reactions of Aldehydes with Cesium Fluoroxysulfate
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Various aromatic and aliphatic aldehydes reacted at 35-40 deg C in CH3CN with CsSo4F giving acid fluorides in a good yield.In some cases formation of fluorohydrocarbons was also observed.Hammett correlation analysis of the transformation of various substituted benzaldehydes (p-OCH3, p-CH3, p-F, p-CF3, m-NO2) gave the reaction constant ρ+ = -0.38.Solvent polarity strongly influenced the conversion of aldehydes into acid fluorides, being in acetonitrile almost quantitative and completely halted in CH2Cl2, n-hexane, or tetrahydrofuran.The presence of nitrobenzene, often used as a radical scavenger, considerably reduced the acid fluoride formation.Based on experimental observations was concluded that the main intermediates involved in the conversion of aldehydes into acid fluorides with CsSO4F must be of a radical nature.
- Stavber, Stojan,Planinsek, Zdenka,Zupan, Marko
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p. 5334 - 5337
(2007/10/02)
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- Catalytic Acid Fluoride Synthesis via Carbonylation of Organic Bromides in the Presence Potassium Fluoride
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Various aryl bromides were carbonylated under an atmospheric pressure of carbon monoxide in DMF in the presence of potassium fluoride to give aroyl fluorides in excellent yields.The carbonylation was promoted by the addition of phase transfer catalysts, but the contamination with water reduced the selectivity.
- Okano, Tamon,Harada, Nobuyuki,Kiji, Jitsuo
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p. 1741 - 1743
(2007/10/02)
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- Perfluoro- and Polyfluorosulfonic Acids. 21. Synthesis of Difluoromethyl Esters Using Fluorosulfonyldifluoroacetic Acid as a Difluorocarbene Precursor
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Difluoromethyl alkanoates 5 and fluorinated and nonfluorinated alkanesulfonates 9 were synthesized in moderate yields by the reaction of alkali metal salts of acids with fluorosulfonyldifluoroacetic acid (3) in acetonitrile under mild conditions.The presumed intermediate anion FO2SCF2CO2- generates CF2: by elimination of SO2, CO2, and F-.The esters are formed by insertion of CF2: into the O-H of the acid, whereas HCF3 is formed by the competing capture of F-.Organic acids can be used indirectly in the reaction in the presence of inorganic salts such as Na2SO4 and KCl, with comparable yields of difluoromethyl esters.
- Chen, Qing-Yun,Wu, Sheng-Wen
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p. 3023 - 3027
(2007/10/02)
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- Cross-interaction Constants as a Measure of the Transition-state Structure. Part 1. The Degree of Bond Formation in Nucleophilic Substitution Reactions
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The kinetic of seven reaction series in methanol involving halides as leaving groups and aromatic amines as nucleophiles are reported.Analyses of various Hammett ρ values, especially the cross-interaction constants ρXY between substituents X in the nucleophile and Y in the substrate, are used to characterize the transition-state structure for the nucleophilic substitution reactions.The degree of bond formation in the transition state as measured by /ρXY/ indicated that the reactions can be classified into two groups according to the magnitude of the cross-interaction constants; the fluoride series gave larger /ρXY/ values indicating a greater degree of bond formation, under the same reactants condition, compared with other series with relatively good leaving groups, e.g.Cl-, Br-, and -OSO2C6H5.When, however, a non-conjugative intervening group such as CO or CH2 is present between the reaction centre and the benzene ring of a reactant, the cross-interaction constant is reduced by a factor of ca. 2, demonstrating the fall-off of the susceptibility of the reaction centres to substituent changes.
- Lee, Ikchoon,Shim, Chang Sub,Chung, Soo Young,Kim, Hyung Yoon,Lee, Hai Whang
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p. 1919 - 1924
(2007/10/02)
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- Low-Resolution Microwave Studies of Substituted Ethyl- and Isopropylbenzenes
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A single conformation exists in ethylbenzenes with the ethyl C-C bond lying in a plane orthogonal to the benzene ring.This conclusion results from the observation that asymmetrically substituted ethylbenzenes each display only a single band series in low-resolution microwave (LRMW) spectra whereas any other conformation of the ethylphenyl fragment would result in two spectroscopically distinguishable species.LRMW spectra of isopropylbenzene derivatives display three spectroscopically distinguishable band series, two of which correspond to the conformation with the methine C-H bond eclipsed with the benzene ring and syn or anti with respect to an unsymmetrical phenyl substituent.The third series is much more intense, has a B + C value which is the average of the syn and anti forms, and is consistent with the superposition of spectra of torsionally excited species.
- True, Nancy S.,Farag, Maya, S.,Bohn, Robert K.,MacGregor, Malcolm A.,Radhakrishnan, J.
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p. 4622 - 4627
(2007/10/02)
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- The Relationship between 19F Substituent Chemical Shifts and Electron Densities: meta- and para-Substituted Benzoyl Fluorides
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The 19F substituent chemical shifts (SCS) of meta- and para-benzoyl fluorides are found to correlate well with substituent parameters using the dual substituent parameter (DSP) equation, indicating that they reflect electronic perturbations induced by the substituent.The direction of the SCS values is such that donating substituents cause upfield shifts whilst acceptors cause downfield shifts.STO-3G calculations indicate that substituents induce only very small changes in ?-electron density about the fluorine atom, but that these changes correlate reasonably well with the observed SCS values.For the para series, the slope of the relationship between Δq?F and 19F SCS is 5000 ppm/electron, indicating the great sensitivity of the fluorine atom to small changes in electron density.
- Brownlee, Robert T. C.,Craik, David J.
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p. 186 - 191
(2007/10/02)
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