- REACTIVE EXTRACTION OF WATER
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Described herein are methods and compounds for extracting water from an aqueous solution. For example, some embodiments include method for extracting water from an aqueous solution, comprising contacting the aqueous solution with a compound comprising one or more carbonyl moieties having an equilibrium constant for a hydration of the carbonyl moiety of at least about 0.5; separating a composition comprising the hydrated compound from the aqueous solution; and reacting the hydrated compound to obtain water.
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Paragraph 0077; 0078
(2020/04/09)
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- Asymmetric Synthesis of Alkyl Fluorides: Hydrogenation of Fluorinated Olefins
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The development of new general methods for the synthesis of chiral fluorine-containing molecules is important for several scientific disciplines. We herein disclose a straightforward method for the preparation of chiral organofluorine molecules that is ba
- Ponra, Sudipta,Yang, Jianping,Kerdphon, Sutthichat,Andersson, Pher G.
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supporting information
p. 9282 - 9287
(2019/05/28)
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- A highly regio- and stereoselective synthesis of ?±-fluorinated imides via fluorination of chiral enamides
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A highly ??-facial selective and regioselective fluorination of chiral enamides is described. The reaction involves an enantioselective fluorination exclusively at the electron-rich enamide olefin with N-F reagents such as Selectfluor and N-fluoro-benzenesulfonimide [NFSI] accompanied by trapping of the ?2-fluoro-iminium cationic intermediate with water. The resulting N,O-hemiacetal could be oxidized using Dess-Martin periodinane, leading to an asymmetric sequence for syntheses of chiral ?±-fluoro-imides and optically enriched ?±-fluoro-ketones.
- Xu, Yan-Shuang,Tang, Yu,Feng, He-Jing,Liu, Ji-Tian,Hsung, Richard P.
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supporting information
p. 572 - 575
(2015/03/04)
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- Development of a generic activation mode: Nucleophilic α-substitution of ketones via oxy-allyl cations
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Oxy-allyl cations have been known as transient electrophilic species since they were first proposed as intermediates in the Favorskii rearrangement in 1894. Since that time, they also have been used as a mode of activation for [4 + 3] cycloadditions in a variety of natural product syntheses. In this manuscript, we describe a method for the interception of oxy-allyl cations with a diverse range of common nucleophiles, thereby demonstrating the value of this intermediate as a generic mode of activation. This simple, mild, room temperature protocol allows for the formation of a variety of high value carbon-carbon and carbon-heteroatom bonds that are readily incorporated within a series of cyclic and acyclic ketone systems. Initial efforts into the development of an enantioselective catalytic variant are also described.
- Vander Wal, Mark N.,Dilger, Andrew K.,Macmillan, David W. C.
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p. 3075 - 3079
(2013/07/26)
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- Enzymatic preparation of (1S,2R)- and (1R,2S)-stereoisomers of 2-halocycloalkanols
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The stereoisomers of cis-2-halocycloalkanols were resolved by a kinetically controlled transesterification with vinyl acetate in the presence of lipases in organic media. High enantioselectivities (ee >98%) and good isolated yields were obtained for all substrates using the appropriate lipase. Burkholderia cepacia lipase was the most efficient enzyme for the resolution of these substrates. The enantiomeric purities of the compounds were defined by derivatization with Mosher's acid and the absolute configurations were determined by chemical correlation.
- Kolodiazhna, Olga O.,Kolodiazhna, Anastasy O.,Kolodiazhnyi, Oleg I.
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- Fluorinated ε-caprolactone: Synthesis and ring-opening polymerization of new α-fluoro-ε-caprolactone monomer
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Fluorinated polyester was synthesized from a novel α-fluoro-ε- caprolactone monomer (α-FCL). The monomer was synthesized from commercially available cyclohexene oxide in three steps. Baeyer-Villiger reaction using 3-chloroperoxybenzoic acid of the corresp
- Al-Azemi, Talal F.,Mohamod, Abdirahman A.
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experimental part
p. 5431 - 5438
(2012/05/20)
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- Conformational analysis of cis-2-halocyclohexanols; Solvent effects by NMR and theoretical calculations
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Conformational problems often involve very small energy differences, even low as 0.5 kcal mol-1. This accuracy can be achieved by theoretical methods in the gas phase with the appropriate accounting of electron correlation. The solution behavio
- Basso, Ernani A.,Abiko, Layara A.,Gauze, Gisele F.,Pontes, Rodrigo M.
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p. 145 - 153
(2011/03/19)
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- Enantioselective organocatalytic α-fluorination of cyclic ketones
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The first highly enantioselective α-fluorination of ketones using organocatalysis has been accomplished. The long-standing problem of enantioselective ketone α-fluorination via enamine activation has been overcome via high-throughput evaluation of a new library of amine catalysts. The optimal system, a primary amine functionalized Cinchona alkaloid, allows the direct and asymmetric α-fluorination of a variety of carbo- and heterocyclic substrates. Furthermore, this protocol also provides diastereo-, regio-, and chemoselective catalyst control in fluorinations involving complex carbonyl systems.
- Kwiatkowski, Piotr,Beeson, Teresa D.,Conrad, Jay C.,MacMillan, David W. C.
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supporting information; experimental part
p. 1738 - 1741
(2011/04/17)
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- Geminal acylation of α-heterosubstituted cyclohexanones and their ketals
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Geminal acylation of derivatives of cyclohexanone with Br, Cl, F, and OCH3 in the α position, and of their corresponding dimethyl ketals, could not be accomplished to a significant extent following published procedures. The transformation was a
- Pottie, Ian R.,Crane, Sheldon N.,Gosse, Anna Lee,Miller, David O.,Burnell, D. Burnell
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body text
p. 1118 - 1124
(2011/01/09)
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- Asymmetric hydrogenation of racemic 2-fluorocyclohexanone over cinchona modified Pt/Al2O3 catalyst
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The first example of enantioselective heterogeneous catalytic hydrogenation of an α-fluoro ketone is reported. The hydrogenation of racemic 2-fluorocyclohexanone over cinchonidine- or methoxycinchonidine-modified Pt/Al2O3 resulted in
- Szori, Kornel,Szoellosi, Gyoergy,Bartok, Mihaly
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p. 255 - 259
(2007/10/03)
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- Nucleophilic substitution reactions of sulfur-substituted cyclohexanone acetals: An analysis of the factors controlling stereoselectivity
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The reactions of cyclohexanone acetals substituted with thiophenyl groups (and other heteroatoms) at C-2 demonstrate the powerful influence that these substituents have on the stereoselectivity of nucleophilic substitution reactions. The trans selectivities of these reactions correlate with the behavior of the corresponding ketones. These experiments lend support to the possibility that the reactions of the acetals, which proceed via oxocarbenium ions, are operating under Felkin-Anh control.
- Billings, Susan B.,Woerpel
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p. 5171 - 5178
(2007/10/03)
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- Direct electrophilic α-fluorination of imines: Efficient synthesis of mono-and difluoroimines
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(Chemical Equation Presented) A mild and efficient procedure to synthesize α-fluoro- and α,α-difluoroimines was developed. Various N-alkylimines derived from acetophenones were successfully monofluorinated using NFSI (N-fluorobenzenesulfonimide) in a mixture of CH3CN and DMF at 0°C. Alternatively, the same procedure without DMF gave rise to difluorinated imines when performed at room temperature. The obtained α- and α,α-difluorinated imines were subsequently reduced to give the corresponding β-fluoro- and β,β-difluoroamines in good yield.
- Verniest, Guido,Van Hende, Eva,Surmont, Riccardo,De Kimpe, Norbert
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p. 4767 - 4770
(2007/10/03)
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- Conformational analysis of 2-halocyclohexanones: An NMR, theoretical and solvation study
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The conformational equilibria of 2-fluoro-, 2-chloro- and 2-iodo-cyclohexanone have been determined in various solvents by measurement of the J2-3 couplings. The observed couplings were analysed using theoretical and solvation calculations to give both the conformer energies in the solvents studied plus the vapour phase energies and the coupling constants in the distinct conformers. These plus previous results for the 2-bromo compound give the conformer energies and couplings of all the 2-halocyclohexanones. In the 2-fluoro compound the axial conformation is the most stable one in the vapour phase (Eeq - Eax = 0.45 kcal mol-1), while the equatorial conformer predominates in all the solvents studied. The other haloketones show similar behaviour, but the energy difference in the vapour phase is larger (Eeq - Eax = 1.05, 1.50 and 1.90 kcal mol-1, for the chloro, bromo and iodo compounds respectively) and the axial conformer is still the prevailing conformer in CCl4 solution for the chloro and bromo ketones and is the major form in all solvents for the iodo compound. The vapour state conformer energies for the fluoro and chloro compounds are in complete agreement with the ab initio calculated energies, but those for the bromo and iodo are not in such good agreement. Both the ab initio calculations and molecular mechanics are used to discuss the origins of the conformer energies. It is shown that the interaction between the C2 halogen and the C=O oxygen in the equatorial conformer is strongly attractive for fluorine, much less so for chlorine, ca. zero for bromine and repulsive for iodine. Comparison of the conformer couplings obtained here with calculated values show generally good agreement.
- Yoshinaga, Fabiana,Tormena, Claudio F.,Freitas, Matheus P.,Rittner, Roberto,Abraham, Raymond J.
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p. 1494 - 1498
(2007/10/03)
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- Diastereoselective electrophilic fluorination of enantiopure α-silylketones using N-fluoro-benzosulfonimide: Regio- and enantioselective synthesis of α-fluoroketones
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α-Fluoroketones 6 are synthesized in good yields and high enantiomeric excesses (ee = 87-≥96%) from the corresponding simple cyclic and acyclic ketone precursors. The procedure involves a regio- and diastereoselective electrophilic fluorination of enantio
- Enders,Faure,Potthoff,Runsink
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p. 2307 - 2319
(2007/10/03)
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- Preparation of alpha -fluoroketones
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PCT No. PCT/GB97/01547 Sec. 371 Date Feb. 5, 1998 Sec. 102(e) Date Feb. 5, 1998 PCT Filed Jun. 6, 1997 PCT Pub. No. WO97/46508 PCT Pub. Date Dec. 11, 1997The use of polar organic solvent as the solvent in the direct fluorination, to make an alpha -fluorok
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- Reaction of silyl enol ethers with xenon difluoride in MeCN: Evidence for a nonclassical radical cation intermediate
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(matrix presented). The reactions of xenon difluoride in MeCN solution in Pyrex flasks with a series of TMS enol ethers have been investigated. The types of products formed are dependent on the structures of individual enol ethers, but under these conditions all products are consistent with a mechanism involving single electron transfer to un-ionized XeF2 giving a radical cation and subsequent formation of an α-fluoroketone, together with some ketone formation. The results suggest that if the radical cation is particularly stable, fluorodesilylation leads to radical formation, and solvent-derived products are then observed. Using other solvents, such as CFCl3 and C6F6, much more complex mixtures of products are obtained, and this is attributed to a different mode of reaction of xenon difluoride involving ionization to FXe+.
- Ramsden, Christopher A.,Smith, Rachel G.
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p. 1591 - 1594
(2008/02/09)
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- Alkylation and decarboxylation of ethyl 2-fluoro-3-oxobutanoate as a route to functionalised α-fluoro-ketones
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Alkylation and decarboxylation of α-fluoro-β-ketoesters such as ethyl 2-fluoro-3-oxobutanoate offers a versatile route to a range of fluoro-ketoalkenes, demonstrating the synthetic utility of using α-fluoro-β-ketoesters as synthons for the preparation of synthetically more sophisticated selectively fluorinated systems.
- Hutchinson,Sandford, Graham,Vaughan, Julian F.S.
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p. 2867 - 2876
(2007/10/03)
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- N-Halogeno compounds part 19: Electrophilic fluorinating agents of the multiple mono-N-fluoro class derived from nitrogen heterocycles
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Bis(4-fluoro-1,4-diazoniabicyclo[2.2.2]oct-1-yl)-ethane and -propane tetratriflates (4, 5), and 1,1′-difluoro-4,4′-bipyridinium ditriflate (6) were prepared by solution-phase direct fluorination of bis(4-aza-1-azoniabicyclo[2.2.2]oct-1-yl)-ethane or -propane ditriflate (10, 11), and 4,4′-bipyridine respectively. The same technique was employed to convert the complex 4,4′-bipyridine · 2BF3 to the mono-NF derivative F3B-NC5H4-C5H4N+-F BF4- (7) and its monomethylated analogue (4-NC5H4)C5H4N+-CH3 TfO- to F-+ NC5H4-C5H4N+-CH3 (TfO- )2 (8). The results of site-specific electrophilic fluorination of some model substrates (1-morpholinocyclohexene, phenol, 2-naphthol, anisole, di-and tri-methoxybenzene) with 5, 7 and 8 are presented.
- Banks, R. Eric,Besheesh, Mohamed K.,Mohialdin-Khaffaf, Suad N.,Sharif, Iqbal
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p. 157 - 161
(2007/10/03)
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- N-halogeno compounds. Part 18. 1-Alkyl-4-fluoro-1,4-diazoniabicyclo [2.2.2] octane salts: User-friendly site-selective electrophilic fluorinating agents of the N-fluoroammonium class
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Methods of synthesis are described for a range of 1-alkyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane salts [R-N+(CH2CH2)3N+-F (X-)2, where R = CH3, CH2Cl, C2H5, CF3CH2, C8H17 and (X-)2 = (TfO-)2, (BF4-)2, (PF6-)2, (TfO-, BF4-), (TfO-, PF6-), (TfO-, FSO3-)] by direct fluorination (with neat F2 at ≤20 mmHg or F2-N2 blends at 1 atm pressure) of monoquaternary salts of 1,4-diazabicyclo[2.2.2]octane [R-+N(CH2CH2)3N X-] or their 1:1 adducts with boron trifluoride, phosphorus pentafluoride, or sulfur trioxide in acetonitrile at ca - 35°C. The results of site-selective electrophilic fluorination of diethyl sodio(phenyl)malonate [→ PhCF(CO2Et)2], 1-morpholinocyclohexene (→ 2-fluorocyclohexanone), phenol (→ 2- and 4-FC6H4OH), 1- and 2-hydroxynaphthalene (→ 2- and 4-FC10H6OH, and 1-FC10H6OH and 1,1-difluoro-2-oxo-1,2-dihydronaphthalene, respectively), acetanilide (→ 2- and 4-FC6H4NHCOCH3), anisole (→ 2- and 4-FC6H4OCH3) and sodium benzenesulfinate (→ PhSO2F) with these N-fluoroammonium salts are presented.
- Banks, R. Eric,Besheesh, Mohamed K.,Mohialdin-Khaffaf, Suad N.,Sharif, Iqbal
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p. 2069 - 2076
(2007/10/03)
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- N-Halogeno compounds. Part 16. Perfluoro-[N-fluoro-N-(4-pyridyl)acetamide] - A new site-selective electrophilic fluorinating agent
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Perfluoro-[N-fluoro-N-(4-pyridyl)acetamide] (2), prepared via direct fluorination of the sodium salt (4) of perfluoro-[N-(4-pyridyl)-acetamide], readily fluorinates diethyl sodio(phenyl)malonate [→PhCF(CO2Et)2], 1-morpholinocyclohexene(→2-fluorocyclohexanone), anisole (→2-and 4-FC6H4OMe), and phenol (→2-and 4-FC6H4OH) under mild conditions. The sodium salt precursor (4) of this side-chain N-F reagent (2) is easily made from pentafluoropyridine via the trifluoroacetylation of its 4-amino derivative or, more directly, by treating it with two equivalents of the monosodium salt of trifluoroacetamide.
- Banks,Besheesh,Tsiliopoulos
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- ANODIC FUNCTIONALIZATION OF VINYL SULFIDES. FORMAL ACCESS TO GEM OR VICINAL ARYL THIOETHER DICATIONS
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The anodic oxidation of a number of vinyl thioethers has been performed in CH3CN-Et3N,3HF.Results clearly show that the reactivity of the vinyl sulfide radical cation depends on several factors as structure of substrates and nucleophilic conditions.For example a dimerization occurred from the unsubstituted vinyl sulfide 1a (CH2=CH-SPh) whereas α,β- and/or β,β-difluoro sulfides were obtained from substituted homologues.In order to understand this reactivity the anodic behaviour of 1a and 1b (Ph-CH=CH-SPh) has been especially analysed in two other nucleophilic media (CH3OH/Et3N,3HF and AcOH/AcOK) leading respectively to methoxylation and acetoxylation of starting compounds.Comparison with electrofluorination results has allowed us to propose a mechanism involving an intermediary episulfonium ion which could explain the formation and ratio of the products isolated.Key Words: vinyl sulfides; enol thioethers; anodic oxidation; electrochemistry; fluorination; methoxylation; acetoxylation; formal dication; fluorosulfides
- Andres, Didier F.,Laurent, Eliane G.,Marquet, Bernard S.,Benotmane, Hassiba,Bensadat, Abdelkader
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p. 2605 - 2618
(2007/10/02)
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- Selective, Electrophilic Fluorinations Using N-Fluoro-o-benzenedisulfonimide
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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)
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- Axial/equatorial proportions for 2-substituted cyclohexanones
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Axial-equatorial conformational proportions have been measured for 2- substituted cyclohexanones in chloroform by the Eliel method for F, Cl, Br, I, MeO, MeS, Me2N, MeSe, and Me. For the first seven of these, at least five experimentally independent measurables were used and the resulting conformational preferences appear to be accurate to within 10%. Systematic errors degraded the results for MeSe and Me. For Me2N, the conformational preference also was measured for the first time at slow exchange in the low- temperature 13C spectrum in several solvents. In chloroform, steric and polar effects contribute to the conformational preferences, with steric effects dominant for large groups such as I and MeS.
- Basso,Kaiser,Rittner,Lambert
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p. 7865 - 7869
(2007/10/02)
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- N-fluorosulfonimides and their application as fluorinating agents
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The invention describes N-fluorosulfonimides which are useful as fluorinating agents. The N-fluorosulfonimides are stable, easily synthesized, and allow the introduction of fluorine into organic compounds under mild conditions.
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- 1-Alkyl-4-fluoro-1,4-diazoniabicyclooctane Salts: a Novel Family of Electrophilic Fluorinating Agents
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Members of a new series of solid, easily handled, storable, transportable, commercially viable, site-selective electrophilic fluorinating agents of the +N-F class (tradenamed Selectfluor reagents) have been synthesized via direct fluorination of monoquaternary salts of 1,4-diazabicyclooctane.
- Banks, R. Eric,Mohialdin-Khaffaf, Suad N.,Lai, G. Sankar,Sharif, Iqbal,Syvret, Robert G.
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p. 595 - 596
(2007/10/02)
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- Fluorinated diazabicycloalkane derivatives
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Fluorinated diazabicycloalkane derivative of the following Formula I: STR1 wherein n represents 0, 1 or 2; R represents a quaternizing organic group; each R1, R2, R3, R4 and R5 independently represents hydrogen, C1 -C6 alkyl, aryl, C1 -C6 alkyl-substituted aryl or aryl-substituted C1 -C6 alkyl and each X- independently represents a conterion or 2X- represents a single divalent counterion, are electrophilic fluorinating agents.
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- Method of fluorinating by using N-fluoropyridinium pyridine heptafluorodiborate
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The present invention provides a novel compound represented as STR1 The present novel compound is prepared by reacting fluorine with pyridine-boron trifluoride and is useful as a fluorinating agent in the fluorination of organic compounds.
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- Power and structure-variable fluorinating agents. The N-fluoropyridinium salt system
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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
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p. 8563 - 8575
(2007/10/02)
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- N-HALOGENO COMPOUNDS. PART 9. N-FLUOROQUINUCLIDINIUM FLUORIDE--A NEW ELECTROPHILIC FLUORINATING AGENT
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N-Fluoroquinuclidium fluoride, prepared in high yield by treatment of a cold, dilute solution of quinuclidine in trichlorofluoromethane with fluorine at low pressure in a specially designed, virtually allglass vacuum system, acts as a site-selective electrophilic fluorinating agent towards carbanionic substrates PhCF(CO2Et)2; Me2CLiNO2-->Me2CFNO2; RMgX-->RF (R = Ph, X = Br; R = c-C6H11, X = Cl); CH2CH2OCH2CH2N-CH=CH(CH23CH2-->CH2(CH2)3COCHF; PhSiCl3/F(1-) (in situ)-->PhF>.
- Banks, Ronald Eric,Boisson, Richard Arthur Du,Morton, William David,Tsiliopoulos, Efthimios
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p. 2805 - 2812
(2007/10/02)
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- Synthesis, Regioselective Deprotonation, and Stereoselective Alkylation of Fluoro Ketimines
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Fluoroacetone imines of cyclohexylamine, valinol O-methyl ether, and phenylalaninol O-methyl ether and 2-fluorocyclohexanone imines of cyclohexylamine and phenylalaninol O-methyl ether were prepared.The temperature-dependent, regioselective deprotonation of these imines was employed in highly regioselective alkylation reactions.The deprotonation of fluoroacetone cyclohexylimine on the carbon bearing fluorine yielded only a single stereoisomer as determined by low temperature 19F NMR.In contrast, deprotonation of fluoroacetone O-benzyloximes was not regiospecific under any of the conditions examined.
- Welch, John T.,Seper, Karl W.
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p. 2991 - 2999
(2007/10/02)
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- Photochemistry of 2-Fluoro-2-alkylcyclohexanones. Drastic Effect of Fluorine Substitution
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In the photreactions of 3-(2-oxocyclohexyl)-propionic acid derivatives 1 a pronounced effect of fluorine substitution is found on the ratio of a) Norrish II vs.Norrish I products; b) cyclization vs. cleavage of the Norrish II biradical; c) ketene vs. unsaturated aldehyde formation from the Norrish I biradical.
- Reinholdt, Karin,Margaretha, Paul
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p. 119 - 122
(2007/10/02)
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- N-FLUOROPYRIDINIUM TRIFLATE AND ITS DERIVATES: USEFUL FLUORINATING AGENTS
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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
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p. 4465 - 4468
(2007/10/02)
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- PREPARATION OF α-FLUOROALDEHYDES AND α-FLUOROKETONES USING DILUTE FLUORINE
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Fluorination of silyl enol ethers with 5percent F2 in N2 at -78 deg C in Freon 11 results in the formation of α-fluoroketones and α-fluoroaldehydes.
- Purrington, Suzane T.,Lazaridis, Nicholas V.,Bumgardner, Carl L.
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p. 2715 - 2716
(2007/10/02)
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- Electrophilic Fluorination with N-Fluoroquinuclidinium Fluoride
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N-Fluoroquinuclidinium fluoride (NFQNF), obtainable in ca. 90percent yield by direct low-temperature liquid-phase fluorination of quinuclidine, has been used to deliver 'positive' fluorine to carbanionic sites in a number of organic substrates.
- Banks, R. E.,Boisson, R. A. Du,Tsiliopoulos, E.
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p. 461 - 466
(2007/10/02)
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- FURTHER STUDIES ON THE SYNTHESIS OF α-FLUORO CARBONYL COMPOUNDS
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The trimethylsilyl enol ethers of cycloalkanones and acid esters are converted in high yields (70-90percent) to the corresponding α-fluoro carbonyl derivative using XeF2 in CH2Cl2.Non-cyclic α-hydroxy ketones such as ethyl mandelate are efficiently transformed to the α-fluoro product by DAST and by Ishikawa's reagent.Nucleophilic displacement of halogen by fluoride failed in cyclic systems, giving instead, α,β-unsaturated ketones in DMF or CH3CN (18-crown-6) and 1,2-diones in DMSO, with KF acting as a base.Attempts at DMSO oxidation of I(Br)F adducts failed to give the α-fluoro ketones, but resulted in dehydrohalogenation to the trans-vinyl fluorides.
- Cantrell, Gary L.,Filler, Robert
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- SELECTIVE FLUORINATIONS WITH 1-FLUORO-2-PYRIDONE
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1-Fluoro-2-pyridone has been used to fluorinate selectively enamines and Grignard reagents under mild conditions.
- Purrington, Suzanne T.,Jones, Walda Ann
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- Photoreduction of Cyclic α-Fluoroketones
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Irradiation of the α-fluoroketones 1a and 6a in i-PrOH selectively affords the parent ketone 1b and 6b, respectively.It is concluded that in this solvent heterolytic C-F bond cleavage of the radical -formed by electron transfer to the excited fluoroketone- is a faster process than the subsequent protonation by the cation radical of the solvent.In cyclohexane 1b and 6b are only formed a minor amounts, the fluorinated RH-reduction product 4 now being the major product from 1a.In non-reducing solvents as t-BuOH or benzene 2-fluorocyclohexanone (1a) exhibits a similar behavior as cyclohexanone (1b) on excitation.The quantum yields for α-cleavage are alike for both compounds, but oxetane formation with 2-methylpropene as olefinic component occurs much more readily with 1a than with 1b.
- Reinholdt, Karin,Margaretha, Paul
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p. 2534 - 2539
(2007/10/02)
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- Room Temperature Fluorination of 1,3-Diketones and Enol Acetates with Xenon Difluoride
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Fluorination of 1,3-diketones with xenon difluoride in the presence of the insoluble cross-linked polystyrene-4-vinylpyridine complex with boron trifluoride and insoluble cross-linked polystryrene-4-vinylpyridine resins resulted in the formation of mono- and di-fluoro products, while reactions with enol acetates in the presence of hydrogen fluoride gave α-fluoroketones.
- Zajc, Barbara,Zupan, Marko
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p. 759 - 760
(2007/10/02)
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