- Unbalanced-Ion-Pair-Catalyzed Nucleophilic Fluorination Using Potassium Fluoride
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An unbalanced ion pair promoter (e.g., tetrabutylammonium sulfate), consisting of a bulky and charge-delocalized cation and a small and charge-localized anion, greatly accelerates nucleophilic fluorinations using easy handling KF. We also successfully converted an inexpensive and commercially available ion-exchange resin to the polymer-supported ion pair promoter (A26–SO42–), which could be reused after filtration. Moreover, A26–SO42– can be used in continuous flow conditions. In our conditions, water is well-tolerated.
- Hammond, Gerald B.,Li, Wangbing,Lu, Zhichao,Xu, Bo
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supporting information
p. 9640 - 9644
(2021/12/14)
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- Method for synthesizing alpha-fluorinated ketone through hydrazone aliphatic chain monoketone
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The invention belongs to the technical field of organic synthesis, and provides a method for synthesizing alpha-ketone fluoride through hydrazone aliphatic chain monoketone, which comprises the following steps of: reacting aliphatic chain monoketone with hydrazine hydrate to obtain hydrazone, and reacting hydrazone with a compound represented by formula 2 under a heating condition to complete hydrazone defluorination. The fluorinated product is widely applied to medicines, the reaction conditions are mild, and the process is simple.
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Paragraph 0089-0091
(2021/02/06)
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- Double Enzyme-Catalyzed One-Pot Synthesis of Enantiocomplementary Vicinal Fluoro Alcohols
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A double-enzyme-catalyzed strategy for the synthesis of enantiocomplementary vicinal fluoro alcohols through a one-pot, three-step process including lipase-catalyzed hydrolysis, spontaneous decarboxylative fluorination, and subsequent ketoreductase-catalyzed reduction was developed. With this approach, β-ketonic esters were converted to the corresponding vicinal fluoro alcohols with high isolated yields (up to 92percent) and stereoselectivities (up to 99percent). This new cascade process addresses some issues in comparison with traditional methods such as environmentally hazardous reaction conditions and low stereoselectivity outcome.
- Fan, Jiajie,Lin, Xianfu,Peng, Yongzhen,Wang, Anlin,Wu, Qi,Xu, Jian,Xu, Weihua,Yu, Huilei
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- Fluoro-Substituted Methyllithium Chemistry: External Quenching Method Using Flow Microreactors
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The external quenching method based on flow microreactors allows the generation and use of short-lived fluoro-substituted methyllithium reagents, such as fluoromethyllithium, fluoroiodomethyllithium, and fluoroiodostannylmethyllithium. Highly chemoselective reactions have been developed, opening new opportunities in the synthesis of fluorinated molecules using fluorinated organometallics.
- Colella, Marco,Degennaro, Leonardo,Higuma, Ryosuke,Ishikawa, Susumu,Luisi, Renzo,Nagaki, Aiichiro,Takahashi, Yusuke,Tota, Arianna
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supporting information
p. 10924 - 10928
(2020/05/08)
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- Decarboxylative fluorination of β-Ketoacids with N-fluorobenzenesulfonimide (NFSI) for the synthesis of α-fluoroketones: Substrate scope and mechanistic investigation
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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
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p. 166 - 172
(2017/09/18)
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- Catalytic Promiscuity of Transaminases: Preparation of Enantioenriched β-Fluoroamines by Formal Tandem Hydrodefluorination/Deamination
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Transaminases are valuable enzymes for industrial biocatalysis and enable the preparation of optically pure amines. For these transformations they require either an amine donor (amination of ketones) or an amine acceptor (deamination of racemic amines). Herein transaminases are shown to react with aromatic β-fluoroamines, thus leading to simultaneous enantioselective dehalogenation and deamination to form the corresponding acetophenone derivatives in the absence of an amine acceptor. A series of racemic β-fluoroamines was resolved in a kinetic resolution by tandem hydrodefluorination/deamination, thus giving the corresponding amines with up to greater than 99 % ee. This protocol is the first example of exploiting the catalytic promiscuity of transaminases as a tool for novel transformations.
- Cuetos, Aníbal,García-Ramos, Marina,Fischereder, Eva-Maria,Díaz-Rodríguez, Alba,Grogan, Gideon,Gotor, Vicente,Kroutil, Wolfgang,Lavandera, Iván
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supporting information
p. 3144 - 3147
(2016/03/12)
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- Synthesis of α-Fluoroketones from Vinyl Azides and Mechanism Interrogation
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An efficient and mild fluorination of vinyl azides for the synthesis of α-fluoroketones is described. The mechanistic studies indicated that a single-electron transfer (SET) and a subsequent fluorine atom transfer process could be involved in the reaction.
- Wu, Shu-Wei,Liu, Feng
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supporting information
p. 3642 - 3645
(2016/08/16)
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- One-Pot Synthesis of α-Fluoroketones and 3-Fluoro-2,4-diaryl-furans from Trifluoromethyl β-Diketones via Decarboxylation
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A facile and mild one-pot protocol via decarboxylation of trifluoromethyl β-diketones has been developed for the construction of α-fluoroketones and 3-fluoro-2,4-diarylfurans which are important units in many biologically active compounds and useful precursors in a variety of functional-group transformations.
- Shao, Tongle,Fang, Xiang,Yang, Xueyan
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supporting information
p. 1835 - 1840
(2015/08/06)
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- Metal-free, efficient oxyfluorination of olefins for the synthesis of α-fluoroketones
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A novel oxyfluorination of olefin reactions has been developed. The reactions involve a metal-free and green catalytic system for the synthesis of α-fluoroketones which is an important building block for organic synthesis. Moreover, this reaction system exhibits great functional group tolerance.
- Yang, Qiang,Mao, Liu-Liang,Yang, Bin,Yang, Shang-Dong
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supporting information
p. 3460 - 3463
(2014/07/21)
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- Synthesis of enantiopure fluorohydrins using alcohol dehydrogenases at high substrate concentrations
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The use of purified and overexpressed alcohol dehydrogenases to synthesize enantiopure fluorinated alcohols is shown. When the bioreductions were performed with ADH-A from Rhodococcus ruber overexpressed in E. coli, no external cofactor was necessary to obtain the enantiopure (R)-derivatives. Employing Lactobacillus brevis ADH, it was possible to achieve the synthesis of enantiopure (S)-fluorohydrins at a 0.5 M substrate concentration. Furthermore, due to the activated character of these substrates, a huge excess of the hydrogen donor was not necessary.
- Borzeicka, Wioleta,Lavandera, Ivan,Gotor, Vicente
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p. 7312 - 7317
(2013/08/23)
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- One-pot α-nucleophilic fluorination of acetophenones in a deep eutectic solvent
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Two methods of nucleophilic fluorination to prepare α-fluoroacetophenones from α-bromoacetophenones by using KF with PEG-400 or TBAF with ZnF2 are described. On the fundamental of nucleophilic fluorination, a novel method of one-pot fluorination to prepare α-fluoroacetophenones directly from acetophenones in DES was developed.
- Chen, Zizhan,Zhu, Wei,Zheng, Zubiao,Zou, Xinzhuo
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experimental part
p. 340 - 344
(2010/06/11)
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- Microwave assisted fluorination: an improved method for side chain fluorination of substituted 1-arylethanones
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A two-step, one-pot microwave (MW) assisted fluorination of 1-arylethanones to their corresponding 1-aryl-2-fluoroethanones has been developed. The first step utilises Selectfluor as a fluorinating agent in methanol forming 1-aryl-2-fluoroethanones and their corresponding dimethyl acetals. In the second step, water is added and Selectfluor acts as a Lewis acid in the hydrolytic cleavage of the dimethyl acetals. Compared to the thermal synthesis, the MW assisted method leads to a reduction in reaction time both in the fluorination and for the dimethyl acetal cleavage. Moreover, the one-pot procedure reduces reagent and solvent consumption. The method is best suited for the preparation of 1-aryl-2-fluoroethanones containing substituents that deactivates electrophilic aromatic substitution, however highly electron deficient ketones such as 1-(3,5-dinitrophenyl)ethanone reacts more slowly. Reactions using electron rich aromatic ketones had a low regioselectivity, and also produced fluoroaromatic products.
- Krane Thvedt, Thor H?kon,Fuglseth, Erik,Sundby, Eirik,Hoff, B?rd Helge
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body text
p. 9550 - 9556
(2010/02/27)
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- Ruthenium-catalysed asymmetric transfer hydrogenation of para-substituted α-fluoroacetophenones
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The first examples of asymmetric transfer hydrogenation of α-fluoroacetophenones are reported. Eight para-substituted α-fluoroacetophenones have been reduced using four catalytic systems constructed of [RuCl2(p-cymene)2]2 or [RuCl2(mesitylene)2]2 in combinations with each of the ligands (1R,2R)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine ((R,R)-TsDPEN) and (1R,2R)-N-(p-toluenesulfonyl)-1,2-cyclohexanediamine ((R,R)-TsCYDN). All reactions were performed in both water and formic acid/triethylamine. The highest enantioselectivity was obtained using the (R,R)-TsDPEN ligand in a formic acid/triethylamine mixture, giving the (S)-1-aryl-2-fluoroethanols in high to moderate enantiomeric excess (97.5-84.5%). For this solvent system the presence of electron withdrawing groups in the para position reduced the enantioselectivity. Reactions performed in water generally gave lower enantioselectivity and reaction rate, although RuCl(mesitylene)-(R,R)-TsDPEN yielded the product alcohols with enantiomeric excess in the range of 95.5-76.5%.
- Fuglseth, Erik,Sundby, Eirik,Hoff, B?rd H.
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experimental part
p. 600 - 603
(2009/11/30)
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- Electrophilic and nucleophilic side chain fluorination of para-substituted acetophenones
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para-Substituted α-fluoroacetophenones have been synthesised by three different routes. Electrophilic fluorination of trimethylsilyl enol ethers of acetophenones using Selectfluor (F-TEDA-BF4, 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis-(tetrafluoroborate)) gave high to moderate yield depending on the electronic properties of the substituents. F-TEDA-BF4 mediated fluorination of acetophenones in methanol resulted in a mixture of α-fluoroacetophenones and the corresponding 2-fluoro-1,1-dimethyl acetals. The dimethyl acetals were hydrolysed using trifluoroacetic acid in water to maximise the yield of the product. Nucleophilic fluorination of α-bromoacetophenones using tetrabutylammonium hydrogen bifluoride (TBABF) led to moderate yield when having electron-donating substituents, whereas low yields were experienced when more electron-withdrawing substituents were introduced.
- Fuglseth, Erik,Thvedt, Thor H?kon Krane,M?ll, Maria F?rde,Hoff, B?rd Helge
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p. 7318 - 7323
(2008/12/21)
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- New synthetic routes towards various α-fluorinated aryl ketones and their enantioselective reductions using baker's yeast
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Highly electrophilic dichlorofluoromethyl aryl ketones were obtained by oxidation of dichlorofluoromethyl aryl alcohols. Subsequent dechlorination of these ketones using sodium formaldehyde sulfoxylate (Rongalite) and reductive dehalogenating system SnCl2/Al led to various fluoromethyl aryl ketones and chlorofluoromethyl aryl ketones, respectively. Asymmetric reductions of these fluorinated ketones using the inexpensive baker's yeast produced the corresponding fluoromethyl aryl alcohols with different enantioselectivities.
- Barkakaty, Balaka,Takaguchi, Yutaka,Tsuboi, Sadao
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p. 970 - 976
(2007/10/03)
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- The synthesis of α-fluoroketones by 1,4-additions of mono-fluorinated enamines to Michael acceptors
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Stork enamine reactions are explored with mono-fluorinated enamines derived from α-fluoroacetophenones and pyrrolidine. The resulting enamines react under mild conditions with Michael acceptors (acrylonitrile, methyl acrylate, methyl methacrylate, methyl vinyl ketone and cyclohexenone) to generate a variety of substituted α-fluoroketones.
- Bridge, Colin F.,O'Hagan, David
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- N-Fluoro-bis[(trifluoromethyl)sulfonyl]imide: Electrophilic fluorination of imines and some methyl-substituted pyridines
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Direct fluorination of imines with N-fluoro-bis[(trifluoromethyl)sulfonyl]imide 1 afforded mono and/or difluoroketones without the need of a strong base to first generate the imine anions. Structurally related 2- and 4-methyl-substituted pyridines gave the respective fluoromethyl pyridines with 1. Our results suggest that an enamine intermediate plays a key role in these reactions.
- Ying,DesMarteau,Gotoh
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- Conformational Analysis. Part 22. An NMR and Theoretical Investigation of the gauche Effect in Fluoroethanols
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The ABCX NMR spectrum of the C*CH(OH)*CH2F fragment of 1-(4-bromophenyl)-2-fluoroethanol (BPFE) in eight solvents of different polarities was recorded and fully analysed. 13C and NOE measurements confirmed the assignment of the prochiral methylene protons
- Abraham, Raymond J.,Chambers, Eric J.,Thomas, W. Anthony
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p. 949 - 956
(2007/10/02)
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