1046785-07-2Relevant academic research and scientific papers
Unbalanced-Ion-Pair-Catalyzed Nucleophilic Fluorination Using Potassium Fluoride
Hammond, Gerald B.,Li, Wangbing,Lu, Zhichao,Xu, Bo
supporting information, p. 9640 - 9644 (2021/12/14)
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.
Ruthenium-catalysed asymmetric transfer hydrogenation of para-substituted α-fluoroacetophenones
Fuglseth, Erik,Sundby, Eirik,Hoff, B?rd H.
experimental part, p. 600 - 603 (2009/11/30)
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%.
Microwave assisted fluorination: an improved method for side chain fluorination of substituted 1-arylethanones
Krane Thvedt, Thor H?kon,Fuglseth, Erik,Sundby, Eirik,Hoff, B?rd Helge
experimental part, p. 9550 - 9556 (2010/02/27)
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.
Electrophilic and nucleophilic side chain fluorination of para-substituted acetophenones
Fuglseth, Erik,Thvedt, Thor H?kon Krane,M?ll, Maria F?rde,Hoff, B?rd Helge
, p. 7318 - 7323 (2008/12/21)
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.
