- Divergent Synthesis of α-Fluorinated Carbonyl and Carboxyl Derivatives by Double Electrophilic Activation of Amides
-
A straightforward and divergent entry to α-fluorinated carbonyl and carboxyl derivatives is reported. Upon activation of amides with triflic anhydride and a 2-halo-pyridine and subsequent trapping of the resulting keteniminium ions with nucleophiles followed by a second electrophilic activation with NFSI and final hydrolysis, a range of amides can be transformed to α-fluorinated ketones, esters, and amides under mild conditions. Moreover, this reaction can be performed to yield enantioenriched products with a traceless chiral auxiliary.
- Dubart, Amaury,Evano, Gwilherm
-
supporting information
p. 8931 - 8936
(2021/11/17)
-
- Nickel-Catalyzed Cross-Coupling of Ethyl Chlorofluoroacetate with Aryl Bromides
-
A combinatorial nickel-catalyzed monofluoroalkylation of aryl bromides with the industrial raw regent ethyl chlorofluoroacetate has been developed. The two key factors to successful conversion are the combination of nickel with readily available nitrogen and phosphine ligands and the using of a mixture of different solvents. Mechanistic investigations indicated a new zinc regent might generated in situ and be involved in the reaction process.
- Li, Han,Sheng, Jie,Wu, Bing-Bing,Li, Yan,Wang, Xi-Sheng
-
supporting information
p. 1741 - 1744
(2021/06/01)
-
- Organo-catalyzed Michael addition of 2-fluoro-2-arylacetonitriles
-
An efficient synthesis of a variety of 2-arylacetonitriles containing a fluorinated stereogenic center through organo-catalyzed Michael addition reaction of 2-fluoro-2-arylacetonitriles has been developed. This protocol uses a cheap organocatalyst (DBU) and has a broad substrate scope: α, β-unsaturated ketones, esters, nitriles and sulfones were all successfully reacted. Importantly, water proved to be a good solvent for this reaction.
- Chen, De-Yin,Song, Shuai,Chen, Ling-Yan,Ren, Xinfeng,Li, Ya
-
supporting information
(2021/03/01)
-
- AZABICYCLO AND DIAZEPINE DERIVATIVES FOR TREATING OCULAR DISORDERS
-
The present invention provides in one aspect azabicycio and diazepine derivatives useful as modulators of muscarinic receptors. In another aspect, the present invention provides pharmaceutical compositions for treating ocular diseases, the compositions comprising at least one muscarinic receptor modulator. Formulae (I) & (II):
- -
-
Page/Page column 20
(2019/05/22)
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- Synthesis of 18F-difluoromethylarenes using aryl boronic acids, ethyl bromofluoroacetate and [18F]fluoride
-
Herein, we report the radiosynthesis of 18F-difluoromethylarenes via the assembly of three components, a boron reagent, ethyl bromofluoroacetate, and cyclotron-produced non-carrier added [18F]fluoride. The two key steps are a copper-catalysed cross-coupling reaction, and a Mn-mediated 18F-fluorodecarboxylation.
- Sap, Jeroen B. I.,Wilson, Thomas C.,Kee, Choon Wee,Straathof, Natan J.W.,Ende, Christopher W.am,Mukherjee, Paramita,Zhang, Lei,Genicot, Christophe,Gouverneur, Véronique
-
p. 3237 - 3241
(2019/03/21)
-
- Enantioselective Hydrogen Atom Transfer: Discovery of Catalytic Promiscuity in Flavin-Dependent 'Ene'-Reductases
-
Flavin has long been known to function as a single electron reductant in biological settings, but this reactivity has rarely been observed with flavoproteins used in organic synthesis. Here we describe the discovery of an enantioselective radical dehalogenation pathway for α-bromoesters using flavin-dependent 'ene'-reductases. Mechanistic experiments support the role of flavin hydroquinone as a single electron reductant, flavin semiquinone as the hydrogen atom source, and the enzyme as the source of chirality.
- Sandoval, Braddock A.,Meichan, Andrew J.,Hyster, Todd K.
-
supporting information
p. 11313 - 11316
(2017/08/30)
-
- Copper-Mediated Synthesis of Monofluoro Aryl Acetates via Decarboxylative Cross-Coupling
-
We report the Cu-promoted oxidative cross-coupling of α-fluoromalonate half-esters and aryl boron reagents to deliver mono-fluoro α-aryl acetates under mild conditions (in air at room temperature). The reaction uses a simple, readily available monofluorinated building block to generate arylated compounds with functional groups that are not easily tolerated by existing methods, such as aryl bromides, iodides, pyridines, and pyrimidines.
- Fahandej-Sadi, Anis,Lundgren, Rylan J.
-
p. 2886 - 2890
(2017/12/14)
-
- Decarboxylative fluorination of β-Ketoacids with N-fluorobenzenesulfonimide (NFSI) for the synthesis of α-fluoroketones: Substrate scope and mechanistic investigation
-
Cesium carbonate (Cs2CO3)-mediated decarboxylative fluorination of β-ketoacids using NFSI in the MeCN/H2O mixed solvent system affords α-fluoroketones with a broad scope. Both electron-rich and electron-deficient α-non-substituted β-ketoacids are amenable to this protocol. The mechanistic study indicates that the reaction proceeds through electrophilic fluorination followed by decarboxylation, which is different from the decarboxylative fluorination of normal carboxylic acids.
- Zhang, Rui,Ni, Chuanfa,He, Zhengbiao,Hu, Jinbo
-
p. 166 - 172
(2017/09/18)
-
- Synthesis, Characterization, and Reactivity of Palladium Fluoroenolate Complexes
-
Cross-coupling reactions of aryl groups with α-fluoro carbonyl compounds catalyzed by palladium complexes have been reported, but palladium fluoroenolate intermediates relevant to such reactions have not been isolated or even detected previously. We report the synthesis, structural characterization, and reactivity of a series of C-bound arylpalladium fluoroenolate complexes ligated by monophosphines and bisphosphines. DPPF-ligated arylpalladium fluoroenolate complexes (DPPF = 1,1-bis(diphenylphosphino)-ferrocene) derived from a monofluoroester, a difluoroester, difluoroamides, and difluoroacetonitrile underwent reductive elimination in high yields. Reductive elimination was faster from complexes containing less electron-withdrawing fluoroenolate groups and longer Pd-C(enolate) bonds than from complexes containing more electron-withdrawing fluoroenolate groups and shorter Pd-C(enolate) bonds. The rates of reductive elimination from these C-bound fluoroenolate complexes were significantly faster than those of the analogous trifluoromethyl complexes.
- Arlow, Sophie I.,Hartwig, John F.
-
supporting information
p. 16088 - 16091
(2017/11/22)
-
- Combinatorial Nickel-Catalyzed Monofluoroalkylation of Aryl Boronic Acids with Unactivated Fluoroalkyl Iodides
-
A combinatorial nickel-catalyzed cross-coupling between arylboronic acids and unactived 1-fluoro-1-iodoalkanes has been developed, which demonstrated high efficiency, mild conditions, and excellent functional-group compatibility. Readily available nitrogen and phosphine ligands were combined with a nitrogen source, which in situ generated a variety of easily tunable catalysts to promote the fluoroalkylation for broad scopes of both coupling partners. This new strategy on combinatorial catalysis offers new solutions for nickel-catalyzed cross-coupling reactions.
- Sheng, Jie,Ni, Hui-Qi,Liu, Ge,Li, Yan,Wang, Xi-Sheng
-
supporting information
p. 4480 - 4483
(2017/09/11)
-
- Nickel-Catalyzed Monofluoroalkylation of Arylsilanes via Hiyama Cross-Coupling
-
The first example of nickel-catalyzed monofluoroalkylation of arylsilanes has been developed with readily available fluoroalkyl halides. This novel transformation has demonstrated high reactivity, broad substrate scope, excellent functional group tolerance, and mild reaction conditions. The selective activation of a relatively inert C-Si bond for slow release of aryl carbanion is the key reason for reducing the amount of arylmetal species, which makes this method more promising for fluorine-containing modification of complex bioactive molecules. Mechanistic investigations indicate that a free fluoroalkyl radical is involved in this catalytic cycle.
- Wu, Yun,Zhang, Hao-Ran,Cao, Yi-Xuan,Lan, Quan,Wang, Xi-Sheng
-
supporting information
p. 5564 - 5567
(2016/11/17)
-
- Nickel-catalyzed monofluoromethylation of aryl boronic acids
-
Aryl boronic acids can be monofluoromethylated under nickel catalysis. The utility of this method is demonstrated by the monofluoromethylation of a borylated and acyl-protected derivative of the statin drug ezetimibe. Mechanistic investigations indicate that a fluoromethyl radical is involved in the NiI/NiIII catalytic cycle.
- Su, Yi-Ming,Feng, Guang-Shou,Wang, Zhen-Yu,Lan, Quan,Wang, Xi-Sheng
-
supporting information
p. 6003 - 6007
(2015/05/13)
-
- COMPOUNDS FOR THE TREATMENT OF CNS DISORDERS
-
The invention relates to novel cycloalkyl- or cycloalkenyl-substituted pyrazolopyrimidinones of formula (I), wherein ā is selected from the group A1 consisting of a C3-C8-cycloalkyl group or a C4-C8-cycloalkenyl group, whereby the members of C3-C8-cycloalkyl group being selected from the group of cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptanyl and cyclooctanyl; and the members of the C4-C8-cycloalkenyl group, being selected from cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, cyclooctenyl, cyclopentadienyl, cyclohexadienyl, cycloheptadienyl, cyclooctadienyl, cycloheptatrienyl, cyclooctathenyl, cyclooctatetraenyl. The new compounds shall be used for the manufacture of medicaments, in particular medicaments for improving perception, concentration, learning and/or memory in patients in need thereof. Chemically, the compounds are characterised as pyrazolopyrimidinones with a cycloalkyl-moiety directly bound to the 1 position of the pyrazolopyrimidinone and a second substituent in the 6 position which is bound via an optionally substituted methylene-bridge. Further aspects of the present invention refer to a process for the manufacture of the compounds and their use for producing medicaments.
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Page/Page column 40
(2012/05/20)
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- Palladium-catalyzed cross-coupling of ethyl α-bromo-α- fluoroacetate with arylboronic acids: Facile synthesis of α-aryl-α- fluoroacetate
-
Palladium-catalyzed Suzuki-Miyaura coupling reactions of ethyl α-bromo-α-fluoroacetate with various structurally diverse arylboronic acids using a phosphine ligand proceeded smoothly to afford α-aryl-α-fluoroacetate in moderate to good yields. This method provides a practical and efficient route to diverse α-monofluorinated α-arylcarbonyl compounds. Georg Thieme Verlag Stuttgart New York.
- Guo, Chen,Yue, Xuyi,Qing, Feng-Ling
-
experimental part
p. 1837 - 1844
(2010/08/19)
-
- Process for producing fluoro-compounds
-
The present invention provides a process for producing highly pure fluoro-compounds by making use of less costly and readily handleable N-(2-chloro-1,1,2-trifluoroethyl)diethylamine. The process produces little or no chlorinated by-products. Specifically
- -
-
Page/Page column 3
(2009/02/11)
-
- Preparation of Mono-/Difluorinated Hydrocarbon Compounds
-
Mono- or difluorinated hydrocarbon compounds are prepared from an alcohol or a carbonylated compound by reacting one of these with a fluorinating reagent, optionally in the presence of a base, the fluorinating agent comprising a pyridinium reactant having the following formula (F), wherein R0 is an alkyl or cycloalkyl radical:
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Page/Page column 10
(2009/09/28)
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- 1-HETEROCYCLYL-1,5-DIHYDRO-PYRAZOLO[3,4-D] PYRIMIDIN-4-ONE DERIVATIVES AND THEIR USE AS PDE9A MODULATORS
-
The invention relates to novel 1,6-disubstituted pyrazolopyrimidinones, Formula (I) with Hc is a mono-, bi- or tricyclic heterocyclyl group, the ring members of which are carbon atoms and at least 1, preferably 1, 2 or 3, heteroatom(s), which are selected from the group of nitrogen, oxygen and sulphur, which is in the form of -S(O)r - with r being 0, 1 or 2, and - said heterocyclyl group is or comprises 1 non-aromatic, saturated, or partly unsaturated monocyclic ring which comprises at least 1 heteroatom as ring member and - said heterocyclyl group is bound to the scaffold by said 1 non- aromatic, saturated, or partly unsaturated monocyclic ring which comprises at least 1 heteroatom as ring member. According to one aspect of the invention the new compounds are for the manufacture of medicaments, in particular medicaments for the treatment of conditions concerning deficits in perception, concentration, learning or memory. The new compounds are also for the manufacture of medicaments for the treatment of Alzheimer's disease.
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Page/Page column 163-164
(2009/10/30)
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- Nucleophilic fluorination of triflates by tetrabutylammonium bifluoride
-
(Chemical Equation Presented) Careful examination of nucleophilicity, basicity, and leaving group ability led us to discover the nucleophilic fluorination of triflates by weakly basic tetrabutylammonium bifluoride, which provides excellent yields with minimal formation of elimination-derived side products. Primary hydroxyl groups as well as secondary hydroxyl groups in acyclic chains or in five-membered rings are excellent substrates, whereas benzylic and aldol-type secondary hydroxyl groups give poor yields as a result of the instability of their triflates.
- Kim, Kyu-Young,Bong, Chan Kim,Hee, Bong Lee,Shin, Hyunik
-
p. 8106 - 8108
(2008/12/22)
-
- Versatile application of trifluoromethyl triflate
-
Hydrolytically stable and easy to handle trifluoromethyl triflate was found to be a liquid reservoir of 'masked' difluorophosgene. Anhydrous F- sources cleave the S-O bond in trifluoromethyl triflate yielding quantitatively the trifluoromethanolate salts, being useful trifluoromethoxy group carriers. Reaction of trifluoromethanolates with in situ generated from o-trimethylsilylphenyl triflate benzyne leads to (trifluoromethoxy)benzene and fluorobenzene (ratio 85:15). Whereas an addition of trifluoromethanethiolate anion across a triple bond of benzyne leads to [(trifluoromethyl)sulfanyl]benzene solely.
- Kolomeitsev, Alexander A.,Vorobyev, Mikhail,Gillandt, Hartmut
-
p. 449 - 454
(2008/09/18)
-
- The effect of substituents and operating conditions on the electrochemical fluorination of alkyl phenylacetates in Et3N·4HF medium
-
Selective electrochemical fluorination of alkyl phenylacetates (Ph-CH2-COOR, where R is methyl, ethyl, n-propyl, n-butyl, i-propyl and sec-butyl) under galvanostatic conditions were reported in Et3N·4HF medium. Preparative electrolysis experiments were carried out both in pre-electrolysed dry Et3N·4HF and the same electrolyte medium without pre-electrolysis. Very little hydrolysed fluorinated products were obtained in pre-electrolysed medium where as significant quantities of hydrolysed products leading to fluorinated phenylacetic acid were obtained from Et3N·4HF without pre-electrolysis. Under optimum experimental conditions up to 87% selectivity of monofluoro ester could be achieved. Difluoro alkyl phenylacetate, monofluoro and difluoro phenylacetic acids were the other predominant side products obtained. The hydrolysis appears to be initiated by tautomeric transformation of proton after the initial electro oxidative formation of the cation radical. 19F as well as 1H NMR spectroscopy have been employed to identify the minor constituents formed during the electro oxidative process.
- Ilayaraja,Manivel,Velayutham,Noel
-
p. 185 - 192
(2008/09/17)
-
- PROCESS FOR PRODUCTION OF FLUOROCOMPOUNDS
-
A process for production of fluorocompounds by which high-purity fulorocompounds can be produced with inexpensive and easily handleable N-(2-chloro-1,1,2-trifluoroethyl)diethylamine while inhibiting the formation of chloride by-products, namely, a process
- -
-
Page/Page column 9
(2008/06/13)
-
- Methods for synthesis of dicarbamate compounds and intermediates in the formation thereof
-
Disclosed is a method of making 2-substituted-2-halo-1,3-propanediols via reduction of corresponding malonate compounds. Also disclosed is a method of making 2-substituted-2-halo-1,3-dicarbamate compounds (such as halo derivatives of felbamate, including fluorofelbamate) via reduction of malonate compounds, followed by carbamoylation. Reduction of the malonate compounds is carried out using an electrophilic hydride reagent.
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-
Page/Page column 7
(2008/06/13)
-
- Direct and convenient conversion of alcohols to fluorides
-
Directly mixing primary, secondary, and tertiary alcohols with nC 4F9SO2F-NR3(HF)3-NR 3 in THF or MeCN results in convenient conversion to the corresponding fluorides in high yields. The readily available reagents are easy to handle, and the mild, almost neutral reaction conditions allow for excellent functional group compatibility. A NR3(HF)3/NR3 ratio of ≤ 1:2 gives the highest reactivity.
- Yin, Jingjun,Zarkowsky, Devin S.,Thomas, David W.,Zhao, Matthew M.,Huffman, Mark A.
-
p. 1465 - 1468
(2007/10/03)
-
- Electrochemical partial fluorination of phenylacetic acids esters and 1-tetralone
-
Anodic oxidation of some benzyl derivatives (phenylacetic acids esters) 1, and 1-tetralone 4, using ammonium fluorides or ammonium tetrafluoroborate as fluorine sources and supporting electrolytes and CH2Cl2 as solvent, allowed the i
- Dinoiu, Vasile,Fukuhara, Tsuyoshi,Miura, Kaori,Yoneda, Norihiko
-
p. 227 - 231
(2007/10/03)
-
- Simple procedure for preparation of α-fluoro esters by fluorination of ester enol silyl ethers with perchloryl fluoride
-
Fluorination of ester enol silyl ethers in THF at room temperature using diluted perchloryl fluoride (FClO3) in the presence of ca. 0.5M eq. of t-BuNH2 as an additive produced the corresponding α-fluoro esters in over 80% yields.
- Fujisawa, Hidehito,Takeuchi, Yoshio
-
p. 173 - 176
(2007/10/03)
-
- Preparative-scale enzyme-catalyzed synthesis of (R)-α-fluorophenylacetic acid
-
A preparative-scale asymmetric synthesis of (R)-α-fluorophenylacetic acid, a useful chiral derivatizing reagent, is described. Starting from ethyl α-bromophenylacetate, α-fluorophenylmalonic acid dipotassium salt was prepared in three steps (54% yield), including nucleophilic substitution by the fluoride ion as the keystep. Both the purified form and crude preparation of arylmalonate decarboxylase in E. coli worked well on this substrate, and (R)-α-flurophenylacetic acid (>99% e.e.) was prepared in a quantitative yield.
- Fukuyama, Yasuaki,Matoishi, Kaori,Iwasaki, Masakazu,Takizawa, Eiji,Miyazaki, Mamoru,Ohta, Hiromichi,Hanzawa, Satoshi,Kakidani, Hitoshi,Sugai, Takeshi
-
p. 1664 - 1666
(2007/10/03)
-
- An efficient method for α-monofluorination of carbonyl compounds with molecular fluorine: Use of α-hydroxymethylene substituent as directing and activating groups
-
Molecular fluorine efficiently reacts with α-hydroxymethylene carbonyl compounds to give α-fluoro-α-formyl compounds in a highly site-specific manner. The fluorinated compounds mostly isolated as their hemiacetals with methanol are readily deformylated just by treatment with weak bases affording α-monofluorinated carbonyl compounds. In this fluorination method, the hydroxymethylene group serves not only as a directing group but also as the activating group of carbonyl compounds for fluorination. By this method, a series of α-fluoro carbonyl compounds including esters was synthesized in high yields.
- Kamaya, Hiroshi,Sato, Masayuki,Kaneko, Chikara
-
p. 587 - 590
(2007/10/03)
-
- New method of preparation of fluoro compounds via utilisation of ammonium and phosphonium perfluorocyclobutane ylides as fluorination reagents
-
Ammonium- and phosphoniumperfluorocyclobutane ylides (7-11), easily prepared from perfluorocyclobutene (1) and tertiary amines (2-4) or phosphines (5,6), smoothly react with primary or secondary alcohols (12-18) and carboxylic acids (19, 20) with formation of alkyl fluorides (21-26) or acyl fluorides (27, 28), respectively. A mechanism for the reaction is proposed.
- Pasenok, Sergej V.,De Roos, Marijn E.,Appel, Wolfgang K.
-
p. 2977 - 2982
(2007/10/03)
-
- Effect of fluorine substitution of α-and β-hydrogen atoms in ethyl phenylacetate and phenylpropionate on their stereoselective hydrolysis by cultured cancer cells
-
(±)-Ethyl 2-fluoro-2-phenylacetate was stereoselectively hydrolyzed by cultured cells of several rat cancer cell lines to give the carboxylic acid rich in the R enantiomer. The stereoselectivity increased for (±)-ethyl 2-fluoro-2-phenylpropionate (2b) with all present cell lines and for (±)-ethyl 2-phenyl-3,3,3-trifluoropropionate (3b) with rat hepatoma McA-RH7777 cell line. The stereoselectivity was different for the different cell lines, as McA-RH7777 cells preferred (R)-2b in contrast with the preference towards (S)-2b by other cells such as ras oncogene-transformed rat liver Anr4 cells. These stereoselectivities were different from those for non-fluorinated (±)-ethyl 2-phenylpropionate. Thus fluorine atoms are recognized by ester hydrolases of cancer cells, and fluorine substitution on the acyl group will be useful for making ester-type anticancer prodrugs more specific to cancer cells.
- Yamazaki, Yoshimitsu,Yusa, Shiro,Kageyama, Yu-Ichi,Tsue, Hirohito,Hirao, Ken-Ichi,Okuno, Hiroaki
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p. 167 - 171
(2007/10/03)
-
- Selective, Electrophilic Fluorinations Using N-Fluoro-o-benzenedisulfonimide
-
The synthesis of N-fluoro-o-benzenedisulfonimide (NFOBS, 2) and its use as an "electrophilic" fluorinating reagent with nucleophilic substrates is described and compared with that of N-fluorobenzenesulfonimide (NFSi, 3).NFOBS (2) is prepared in three steps in 81percent overall yield from commercially available o-benzenedisulfonic acid (4) and involves treatment of o-benzenedisulfonimide (6) with dilute fluorine (10percent F2/N2).Reaction of 2 with metal enolates, silyl enol ethers, and 1,3-dicarbonyl compounds affords the corresponding α-fluoro compounds in yields up to 95percent, with good control of mono- and difluorination.Fluorination of ortho-metalated aromatic compounds was achieved in modest to good yields (10-80percent).While the reactivities of 2 and 3 are similar, better yields were observed with the former reagent in the fluorination of metal enolates, Grignard and lithium reagents, while 3 gave better results with the ortho-lithiated aromatic substrates.The available evidence suggests an SN2-type mechanism for the fluorination of nucleophilic substrates by these reagents.
- Davis, Franklin A.,Han, Wei,Murphy, Christopher K.
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p. 4730 - 4737
(2007/10/02)
-
- Microbial asymmetric decarboxylation of fluorine-containing arylmalonic acid derivatives
-
α-Methyl-α-(trifluoromethylphenyl)malonic acids have been incubated with Alcaligenes bronchisepticus to afford optically active α-arylpropionic acids.Generally, the chemical and optical yields of the reaction products were higher when the substituents on the aromatic ring were strongly electron-withdrawing.Decarboxylation of α-fluoro-α-phenylmalonic acid with the aid of the same bacterium afforded optically active α-fluoro-α-phenylacetic acid.
- Miyamoto, Kenji,Tsuchiya, Shigeo,Ohta, Hiromichi
-
p. 225 - 232
(2007/10/02)
-
- Electrochemistry of Ethyl α-Bromo-α-fluoro(phenyl)acetate and some Ethyl α-Bromo(trifluoromethylphenyl)acetates and Electrochemical Synthesis of the Corresponding Diastereoisomeric Diethyl Succinates.
-
Ethyl α-bromoesters (1)-(5) (ABr) were prepared through NBS bromination of (6)-(10) (AH) respectively.Controlled potential electrolysis of (1)-(5), dissolved in dry dimethylformamide (DMF) containing Et4NClO4 (0.1 M) allows the corresponding succinates (1
- Mattiello, Leonardo,Rampazzo, Liliana,Sotgiu, Giovanni
-
p. 2732 - 2754
(2007/10/02)
-
- Power and structure-variable fluorinating agents. The N-fluoropyridinium salt system
-
The usefulness of the N-fluoropyridinium salt system as a source of fluorinating agents was examined by using substituted or unsubstituted N-fluoropyridinium triflates 1-11, N-fluoropyridinium salts possessing other counteranions 1a-d and 3a, and the counteranion-bound salts, N-fluoropyridinium-2-sulfonates 12 and 13. Electrophilic fluorinating power was found to vary remarkably according to the electronic nature of the ring substituents. This power increased as the electron density of positive nitrogen sites decreased, and this was correlated to the pKa values of the corresponding pyridines. By virtue of this variation, it was possible to fluorinate a wide range of nucleophilic substrates differing in reactivity. It is thus possible to fluorinate aromatics, carbanions, active methylene compounds, enol alkyl or silyl ethers, vinyl acetates, ketene silyl acetals, and olefins through the proper use of salts pentachloro 6 through 2,4,6-trimethyl 2, their power decreasing in this order. All the reactions could be explained on the basis of a one-electron-transfer mechanism. N-Fluoropyridinium salts showed high chemoselectivity in fluorination, the extent depending on the reactive moiety. In consideration of these Findings, selective 9α-fluorination of steroids was carried out by reacting 1 with tris(trimethylsilyl ether) 73 of a triketo steroid. Regio- or stereoselectivity in fluorination was determined by a N-fluoropyridinium salt structure. Steric bulkiness of the N-F surroundings hindered the ortho fluorination of phenols and aniline derivatives, while the capacity for hydrogen bonding on the part of the counteranions prompted this process, and the counteranion-bound salts 12 and 13 underwent this fluorination exclusively or almost so. Both bulky N-fluoropyridinium triflates 2 and 7 preferentially attacked the 6-position of the conjugated vinyl ester of a steroid from the unhindered β-direction to give a thermally unstable 6β-fluoro isomer. On the basis of these results, N-fluoropyridinium salts may be concluded to constitute a system that can serve as a source of the most ideal fluorinating agents for conducting desired selective fluorination through fluorinating capacity or structural alteration.
- Umemoto, Teruo,Fukami, Shinji,Tomizawa, Ginjiro,Harasawa, Kikuko,Kawada, Kosuke,Tomita, Kyoichi
-
p. 8563 - 8575
(2007/10/02)
-
- ELECTRFLUORATION EN POSITION BENZYLIQUE DANS LE SULFOLANE
-
The use of sulfolane as a solvent instead of acetonitrile in the electrofluorination of benzylic derivatives 1, (R=H, Cl) gives greater yields of benzylic fluorides 2, since the formation of acetamide byproducts 4 is prevented.However, the parallel fluorination of the aromatic nucleus is not avoided under these conditions.
- Laurent, Eliane,Marquet, Bernard,Tardivel, Robert
-
p. 115 - 126
(2007/10/02)
-
- N-FLUOROPYRIDINIUM TRIFLATE AND ITS DERIVATES: USEFUL FLUORINATING AGENTS
-
N-Fluoropyridinium triflate and its derivates, stable and nonhygroscopic crystals, were found to be widely applicable reagents for mild and selective fluorination of a variety of organic compounds.
- Umemoto, Teruo,Kawada, Kosuke,Tomita, Kyoichi
-
p. 4465 - 4468
(2007/10/02)
-
- 1-Fluoro-2-pyridone: A Useful Fluorinating Reagent
-
1-Fluoro-2-pyridone (mp 50-53 degC) has been prepared by reaction of 5percent fluorine in nitrogen and 2-(trimethylsiloxy)pyridine in FCCl3 at -78 degC.After sublimation, the pyridone is used as a selective fluorinating agent in the preparation of some fl
- Purrington, Suzanne T.,Jones, Walda Ann
-
p. 761 - 762
(2007/10/02)
-
- Synthesis of α-fluorocarbonyl compounds
-
Process for preparing an organic compound of the formula R2 R2 CFC(O)R3, which process comprises contacting and reacting in a reaction mixture which includes an inert solvent, at a temperature of -40° C. to -100° C., ROF and STR1 R is polyfluoroperhaloalkyl of 1-6 carbon atoms or FOCF2 ; R1 is hydrocarbyl of 1-6 carbon atoms; each R2 is selected from H, alkyl of 1-17 carbon atoms, cycloalkyl of 3-6 carbon atoms, aryl, heteroaryl and such alkyl, cycloalkyl, aryl and heteroaryl substituted by halogen or alkoxy of 1-6 carbon atoms; R3 is selected from H, alkyl and haloalkyl of 1-16 carbon atoms, cycloalkyl of 3-10 carbon atoms, aryl and haloaryl, OSi(R1)3, OH, NH2, alkoxy of 1-6 carbon atoms, aryloxy, NHR1 and NR12 wherein R1 is alkyl of 1-6 carbon atoms, N-arylamino and nitrogen or sulfur heterocyclic of 4-5 carbon atoms; R3 and one R2 taken together is a diradical which with the C=C group is carbocyclic, heterocyclic or haloheterocyclic, and recovering from the reaction mixture the compound of the formula R2 R2 CFC(O)R3.
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