5-fluoro-l-

Fluoronaphthalene [321-38-0] is prepared from 1-naphthylamine by the Balz-Schiemaim reaction in 52% yield or by diazotization in anhydrous hydrogen fluoride in 82% yield. Electrophilic substitution occurs at the 4-position, eg, nitration with fuming nitric acid in acetic acid gave 88% yield of l-fluoro-4-nitro-naphthalene [341 -92-4]. 

Studies of alkyl halide-lithium alkyl reactions have been almost wholly concerned with proton polarization. The one exception to date is an investigation of polarization in the reaction of n-butyl lithium with p-fluorobenzyl chloride giving p,p -difluorobibenzyl (A/E multi-plet) and l-fluoro-4-pentylbenzene (E/A) (Rakshys, 1970). Surprisingly H-polarization is not observed. 

In sharp contrast to the KOCH3/CH3OH system, the KOt-Bu/t-BuOH combination is quite sensitive to the presence of cation-complexing agents, as was shown by Del Cima et al. (1973). Whereas on addition of ([20] + [21]), the rate of displacement of fluorine by reaction with KOt-Bu increased by only a factor of 3 in the case of l-fluoro-2-nitrobenzene, it increased by a factor of 1.4 x 103 for l-fluoro-4-nitrobenzene (Table 23). Consequently, the... 

For liquid-phase reactions it is known that they may be enhanced by applying higher pressures if the activation volumes are strongly negative, for example, with Diels-Alder reactions. At pressures up to 600 bar (6 x 10 Pa), Benito-Lopez et al. used fiber-based on-line UV-vis spectroscopy to monitor the nucleophilic aromatic substitution of l-fluoro-4-nitrobenzene with a ten-fold excess of pyrrolidine. ... 

It was found that the counteranion of the 1-fluoropyridinium salts considerably affects selective fluorinations.54 For example, fluorination with 1-fluoropyridinium triflate (la) was compared to that with l-fluoro-4-methylpyridinium-2-sulfonate (2b) using a steroid 10 containing an acetoxy function and a conjugated trimethylsilyl enol ether as the substrate.54... 

Flow fluorination of the 4,4 -bipyridine —boron trifluoride complex gives only mono-fluorinated l-fluoro-4-(4-pyridyl)pyridinium boron trifluoride tetrafluoroborate (31), while fluorination of l-methyl-4-(4-pyridyl)pyridinium triflate in the presence of lithium triflate provides l-fluoro-l -methyl-4,4 -bipyridinium ditriflatc (32) 67... 

Table 5. Fluorination of Aromatic Compounds with l-Fluoro-4-(4-pyridyl)pyridinium Boron Trifluoride Tetrafluoroborate (31) and l-Fluoro-l -methyl-4,4 -bipyridinium Ditriflate (32)67...

The bridgehead-amine-derived electrophilic fluorinating reagents l-alkyl-4-fluoro-l,4-di-azoniabicyclo[2.2.2]octane ditriflate 5 a or bis(tetrafluoroborates) 5b and 6 can be prepared from l-alkyl-4-aza-l-azoniabicyclo[2.2.2]octane salts and elemental fluorine. For example, treatment of l-methyl-4-aza-l-azoniabicyclo[2.2.2]octane triflate (4a) and lithium triflate in acetonitrile at — 35CC with neat fluorine over three hours gives l-fluoro-4-methyl-l,4-dia-zoniabicyclo[2.2.2]octane ditriflate (5a).81 The reagents 5b, 6, 7, and 8 can be synthesized in a similar manner.76 83... 

Table 10. Direct a-Fluorination of Ketones Using l-Fluoro-4-hydroxy-l,4-dia-zoniabicyclo[2.2.2]octane Bis(tetrafluoroborate) (NFTh, 21)96...

The second product in this reaction, the difluorotris(perfluoroalkyl)-A5-phosphane, does not dissolve in aryl fluorides and, because of its greater density, forms a lower layer which can be easily separated. In this way the difluoro-A5-phosphanes are regenerated almost quantitatively and can be used in the synthesis many times. An example is the decomposition of 4-nitrobenzene-diazonium trifluorotris(heptafluoropropyl)phosphate at 87 C which provides l-fluoro-4-ni-trobenzene in 82% yield and difluorotris(heptafluoropropyl)-A5-phosphane in quantitative yield.6 This method is a convenient modification of the Balz-Schiemann reaction (see Section 26.1.3.). 

The nucleophilic displacement of halogens in aromatic compounds by fluorine is aided by utilizing an appropriate catalyst. Polymer-supported aminopyridinium salts have been found to be versatile catalysts for the synthesis of aryl fluorides. The advantage of the catalyst is that it can be recycled and used again. l-Chloro-4-nitrobenzene (3) is converted to l-fluoro-4-nitrobenzene (4) in 71 % isolated yield using this method. The catalyst used has the structure 5.91... 

Tetrabutylphosphonium hydrogen difluoride [Bu4PF (HF)] and dihydrogen trifluoride [Bu4PF (HF)2] have been shown to be expedient reagents for nucleophilic fluorination of aromatic substrates containing a chlorine or bromine atom or a nitro group under mild conditions in non polar solvents. Thus, for example l-chloro-4-nitrobenzene (28) is converted to l-fluoro-4-nitrobenzene (29) in 90% yield.219... 

In substitution reactions of the carbonyl oxygen, boron trifluoride has been used as a reagent. 4-Fluorobenzoyl chloride (5) can be converted to the corresponding fluoride 6 in addition to remarkable amounts of l-fluoro-4-(trifluoromethyl)benzene (7),10 however, this conversion does not appear to be generally useful. 

Decomposition of the diazonium trifluorotris(perfluoroalkyl)phosphates proceeds mildly, without formation of tars (since no strong Lewis acid evolves), and with high yields of the substituted fluorobenzenes. For example, l-fluoro-4-nitrobenzene is obtained in a far better yield (82%) than from 4-nitrobenzenediazonium hexafluorophosphate or tetrafluoroborate [cf. formation of 2 (R = 4-N02)]. The coproduced difluorotris(perfluoroalkyl)-A5-phosphanes are not soluble in the resulting fluorobenzene derivatives and, because of their high density, form a lower layer which is readily separated. Thus, these difluoro-25-phosphanes can be regenerated quantitatively and used repeatedly. 

To a stirred solution of NH4C1 (1.25 g) in H20 (40 mL) was added fluoronitrobenzene (2.85 g, 23 mmol). Zn powder (2.95 g, 45 mmol) was added portionwise over 15 min and the mixture was heated to reflux for some time. ZnO was filtered off from the warm mixture and the filtrate was mixed with a solution of FeCl3 (5.5 g) in ice water (135 mL). The precipitate was filtered off, dried between filter paper sheets, crystallized (EtOH), and steam-distilled to give pure 8 yields l-fluoro-2-nitrosobenzene, 49% mp 19 C l-fluoro-3-nitrosobenzene, 87% mp 51 C l-fluoro-4-nitrosobenzene, 89% mp 39 C. 

Fluorine atoms in electron-deficient benzene derivatives, such as l-fluoro-2-nitroben-zene,149-150 l-fluoro-4-nitrobenzene.151 153 2-fluorobenzaldchyde,154"156 2-fluoroaceto-phenone,155156 4-fluoroacetophenonc,157 2-fluorobenzophenone.156 2- and 4-fluorobenzoni-trile,158 and 4-fluorophenyl trifluoromethyl sulfone,152,159 are easily substituted by N-nucleophiles. Even fluorine in electron-deficient sandwich complexes, such as tricarbonyl(t/6-fluoro-benzene)chromium (3), is substituted by amines.160161... 

Phosphonoic Acid l-Fluoro-4-hydro y-3-oxo-l-bulene E10b2. 363 (-HE En C = N2 CH-OH)... 

Bronio-octafluoi o-l-tn fluoiomcthyl-ElOa. 530 (Educt) 6-(3-Butenyl)-l-fluoro-4-phenyl-ElOa. 226 (SnR, -> F) ElOb,. 293/296 (SnR, -> F)... 

Benzyloxy-meihyl)-8(or 7)-fluoro-7(oi 8)-hydroxy- ElObj. 144 (Oxirane + HF) 3-(l-Fluoro-4-mcihoxvcarbonyN butvl)-3-mcthoxy-7-trietIiyIsilyl-oxy-6-(3-triethylsilyloxy-l-octenyl)- ElOa, 268 (En +... 

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