The new convenient synthesis of fluorinated Penciclovir analogues 9-(4-fluoro-3-hydroxymethylbutyl) guanine (FHBG) and 2-amino-6-fluoro-9-(4-hydroxy-3-hydroxymethylbutyl) purine (6-Fluoropenciclovir) ...were described.
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9-(4-Hydroxy-3-hydroxymethylbutyl) guanine (Penciclovir) is a potent and selective inhibitor of members of the herpes virus family. A new convenient synthesis of fluorinated Penciclovir analogues 9-(4-fluoro-3-hydroxymethylbutyl) guanine (FHBG) and 2-amino-6-fluoro-9-(4-hydroxy-3-hydroxy-methylbutyl) purine (6-Fluoropenciclovir) were described. The structures of the products were characterized by UV, IR,
1H NMR,
19F NMR spectra and MS.
A rapid synthesis of 2′,3′-dideoxy-3′-fluoro-beta-D-threo-nucleosides bearing the pyrimidine canonical bases of nucleic acids has been developed in order to discover new nucleoside derivatives as ...potential antiviral.
A rapid synthesis of 2′,3′-dideoxy-3′-fluoro-β-
d-
threo-nucleosides bearing the pyrimidine canonical bases of nucleic acids has been developed in order to discover new nucleoside derivatives as potential antiviral drugs. However, when evaluated for their antiviral activity in cell culture experiments, none of these compounds showed any significant antiviral activity.
Organic field-effect transistors (OFETs) based on ir-conjugated systems have been a great interest in recent years as they are indispensable components in organic electronics. In this con-text, a ...novel synthetic route to electronegative units: hexafluorocyclopenta c thiophene, 4, 4-diflu-oro-4H-cyclopenta 2, 1-b:3, 4-b' dithiophene, 6, 6, 12, 12-tetrafluoroindeno 3, 2-b fluorene, difluoro-dioxocyclopenta c thiophene, and difluorodioxocyclopenta b thiophene have been accomplished by the use of fluorination reactions as a key step. The oligomers containing these units also have been synthesized to elucidate the precise structure-property-FET characteristics relationships. The annelation of the electron-withdrawing groups effectively lowers the LUMO energy levels without disrupting the effective conjugation of the backbones, which was unambiguously clarified by spectroscopic and electrochemical measurements as well as X-ray analyses. These electroneg-ative oligothiophenes exhibited n-type semiconducting behavior with high field-effect electron mobilities.
This chapter is organized based on the nature of the electrophile and then subdivided by the type of products obtained from the substitution. It covers reaction of nitrogen electrophiles, sulfur ...electrophiles, halogenation, and carbon electrophiles. A feature of nitrogen electrophilic reaction is that it directly functionalizes an arene C‐H bond, and the reagent used, nitric acid, is inexpensive. Another advantage of the nitration reaction is that the active nitrating species, the nitronium ion, is very reactive, and the reaction typically stops after a single nitration due to the deactivating effect of a nitro substituent. While the sulfonation reaction is not utilized as often as the chlorosulfonation, this transformation allows for the direct formation of a sulfonic acid. Sulfonation is conducted in fuming sulfuric acid, a highly corrosive reagent. Electrophilic fluorination of arenes is not a very common reaction. Several of the reagents used for electrophilic fluorination are not practical or present safety concerns for scaling.
Fluoride layers have been known to contribute to the selective permeability of hydrogen molecules in the gas–solid reaction and provide a protective barrier against impurities such as water vapor, ...carbon monoxide, air, and others. One of the important roles of the fluorination processes is the removal of the oxide layer from the surface which considerably improves the initial charge/discharge characteristics. However, it has also been found that during fluorination, metallic Ni on the surface dissolves rapidly into the aqueous F
− and HF
2
− ion containing solution (here after, denotes F-solution) and as the result, the electric conductivity is significantly reduced in the fluoride layer. This paper is aimed at investigating the effects of fluorination conditions on the electrochemical properties and characteristics of the AB
5 electrodes for Ni–metal hydride batteries. Special care has been taken to control fluoride formation and its thickness on the particle surface. Ni
2+ ions were added to the F-solution in order to protect Ni from being dissolved and lost in the vicinity of the particle surface. The thickness of the fluoride layer depends largely upon the specific surface area to be treated as a function of time. The thickness of the fluoride layer and the state of metallic Ni near the surface region was investigated by EPMA and ICPS and they were correlated with the initial discharge capacity, charge/discharge cycle life, and durability, against a 6 M KOH electrolyte solution.
A combination of silver nitrate (AgNO3) catalyst and Selectfluor® was found to perform radical deoxyfluorination of cesium oxalates derived from corresponding alcohols. The reaction tolerates a wide ...range of functional groups and provides preferentially access to tertiary alkyl fluorides.
Readily available from alcohols, cesium oxalates undergo radical deoxyfluorination reaction in the presence of silver salts catalyst and Selectfluor® to produce alkyl fluorides. Herein, the scope of the fluorination protocol and a brief mechanistic study is described.
The objective of this study was to investigate Al particle reactivity as a function of the Al2O3 shell phase. Aluminum particles were thermally treated to transition the shell from amorphous to ...crystalline and each powder was combined with polytetrafluoroethylene (PTFE). Flame speeds were measured for Al + PTFE powder mixtures for two Al particle sizes that differ from micrometer (μAl) to nanometer (nAl) diameter and for both crystalline and amorphous Al2O3 shells encapsulating Al core particles. Results showed that μAl particles were more sensitive to shell phase than nAl particles. Reactions were modeled according to the melt dispersion mechanism (MDM), and altering the shell phase reduced the thickness, damaged the shell structure, impeded melt dispersion, and reduced flame speed for μAl particles by 45% and nAl particles by 12%.
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•Al + PTFE flame speeds were measured for different Al2O3 shell phases.•For nAl particles, there was 12% reduction in flame speed with shell phase.•For μAl particles, there was a 45% reduction in flame speed with shell phase.•Melt dispersion mechanism was activated in all reactions.
•DAST in fluorination reactions of 4-(formyl) and 4-(hydroxymethyl) 3-aryl-1H-1-phenylpyrazoles.•Mono- and difluoromethyl groups insertion at C4 position of phenylpyrazoles.•New ...3-aryl-4-(di)fluoromethyl-1H-1-phenylpyrazoles are synthesized.•Fluorinated compounds 1H, 13C and 19F spin-spin coupling NMR spectra assignments are presented and discussed.•New 19F NMR assignments for the fluoromethyl groups at C4 position of phenylpyrazoles.
This paper reports a synthetic and NMR spectroscopic studies of two new series of 4-fluorinated 1,3,5-substituted 1H-pyrazoles. Firstly, an efficient synthesis of new series of 3-aryl-4-(di)fluoromethyl-1H-1-phenylpyrazoles, where aryl=Ph, 4-NO2C6H4, 4-CH3OC6H4 is described, from fluorination reactions of 4-(formyl)- and 4-(hydroxymethyl)-1H-1-phenylpyrazoles in dichloromethane as solvent at room temperature, employing diethylaminosulfur trifluoride (DAST) as fluorinating agent in 41 to 73% yield. The 4-formyl-pyrazoles are obtained in 54–58% yield by Vilsmeier–Haack reaction using a mixture of POCl3/DMF with arylhydrazones, which were derived from the respective aryl methyl ketones and phenylhydrazine. The 4-hydroxymethyl-pyrazole precursors were easily obtained from the reduction of 4-formyl-pyrazoles by sodium borohydride (NaBH4) in 52–87% yield. Subsequently, the present work also discusses the 1H, 13C and 19F NMR spectroscopic data.
This chapter contains sections titled:
Difluoromethylation and Halodifluoromethylation
The Perfluoroalkoxy Group
The Perfluoroalkylthio Group and Sulfur‐Based Super‐Electron‐Withdrawing Groups
The ...Pentafluorosulfanyl Group and Related Structures
References
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