Fluorophenols, oxidation

Less activated substrates such as uorohaloben2enes also undergo nucleophilic displacement and thereby permit entry to other useful compounds. Bromine is preferentially displaced in -bromofluoroben2ene [460-00-4] by hydroxyl ion under the following conditions calcium hydroxide, water, cuprous oxide catalyst, 250°C, 3.46 MPa (500 psi), to give -fluorophenol [371-41-5] in 79% yield (162,163). This product is a key precursor to sorbinil, an en2yme inhibitor (aldose reductase). 

In the course of this study, the authors determined /Lvalues for dibenzyl, methyl phenyl, methyl p-nitrophenyl, di-p-tolyl, di-isopropyl and tetramethylene sulphoxides and for diethyl, dipropyl and dibutyl sulphites. The /Lscales are applied to the various reactions or the spectral measurements. The /Lscales have been divided into either family-dependent (FD) types, which means two or more compounds can share the same /Lscale, family-independent (FI) types. Consequently, a variety of /Lscales are now available for various families of the bases, including 29 aldehydes and ketones, 17 carboxylic amides and ureas, 14 carboxylic acids esters, 4 acyl halides, 5 nitriles, 10 ethers, 16 phosphine oxides, 12 sulphinyl compounds, 15 pyridines and pyrimidines, 16 sp3 hybridized amines and 10 alcohols. The enthalpies of formation of the hydrogen bond of 4-fluorophenol with both sulphoxides and phosphine oxides and related derivatives fit the empirical equation 18, where the standard deviation is y = 0.983. Several averaged scales are shown in Table 1588. 

Oxidations of [ F]Fluorobenzaldehydes to [ F]Fluorophenols. . 228 Decarbonylation of F-Aromatic Aldehydes and AppHcations. . 229... 

Monofluorinated hydroquinone and quinone are obtained by stepwise oxidation of 2-fluorophenol(l) using different oxidation agents.167 In the first stage, potassium peroxydisulfate is applied and the resulting hydroquinone 2 is further oxidized to 3 by ammonium cerium(IV) nitrate.167... 

The cerium(IV) oxidation of lactyllactic acid49 and of 4-oxopentanoic acid50 in aqueous nitric acid solutions shows first-order dependence of the reaction on both cerium(IV) and substrate. A 1 1 complex formation between manganese(III) and amine, which later decomposes in the rate-limiting step, best explains the kinetics of oxidation of aliphatic amines by cerium(IV) in nitric acid medium in the presence of manganese(II).51 The kinetics of oxidation of naphthalene, 2-methyhiaphthalene, and a-naphthol with cerium(IV) in perchloric acid solutions have been studied.52 Use of a 50-fold molar excess of cerium(IV) perchlorate results in complete oxidation of fluorophenols to CO2, HCO2H, and HF in 48 h at 50 °C.53... 

Oxidative fluorination.1 Reaction of phenol with Pb02 (2 equiv.) and HF/ pyridine (70/30, w/w) in CH2CI2 at 25° provides the dienone 1 in 30% yield. It can undergo Michael addition and aromatization to give substituted p-fluorophenols. 

The effect of the halogen substituent (fluoro, chloro, bromo and iodo) on the yield and mechanism of 4-halophenol photolysis was investigated by Durand et al. [24], Transient spectroscopy in aerated aqueous solutions indicated the formation of p-benzoquinone O-oxide from each derivative except 4-iodophenol for which no transients were detected p-benzoquinone and hydroquinone were found as photoproducts for all four compounds. It was concluded that the carbene mechanism was valid for the whole series. Under continuous irradiation, the 4-halophenol degradation quantum yields were determined to be

fluorescence lifetimes decreased in the same order, from 2.1 ns for 4-fluorophenol to 0.4 ns for 4-chlorophenol and < 0.1 ns for 4-bromophenol. 

Krbisbl G, Schmidt M (1999) Wet Chemical UV Oxidation of 2-Fluorophenol Optimization with Chosen Reaction Parameters, Chem. Eng. Technol. 22, No. 12 1001-1006. Krutzlbr T, Baubr R (1999) Optimization of a Photo-Fenton Prototype Reactor, Chemosphere 38, No. 11 2517-2532. 

Kreisel G, Schmidt M (1999) Wet Chemical UV Oxidation of 2-Fluorophenol Optimization with Chosen Reaction Parameters,... 

A similm methodtdqgy was used by Boichardt and coworkers in the synthesis of the phenol (26 Scheme 11). Here, the fact that 4-fluorophenol metallates next to fluorine when the phenol is protected as a TBDMS ether was put to good use for introduction of the hydroxy group, likewise, oxidation of a boron complex was a key step in the synthesis of phenolic dihydrodiols of benzo[a]pyrene, (27) and... 

Modified high-silica zeolites are used for selective oxidation of mono- and difluorobenzenes into corresponding fluorophenols using nitrous oxide as an oxidant. The nature of the active sites and the reaction mechanism are discussed. 

For comparison, we tested also the sample of the crystalline Ga-silicalite writh the ZSM-5 type structure in the reaction of fluorobenzene oxidation. The catalytic data are presented in Table 1. It is seen that, under optimal conditions at 670 K, the conversion of fluorobenzene is 20% at an excellent selectivity to fluorophenol close to 97-98%. The regioselectivity of this catalyst is similar to that of the H[AI]ZSM-5 catalyst, i.e., the p-isomer of fluorophenol predominates in the reaction products. 

The synthesis of sodium channel inhibitor 1 [82] illustrates the utility of the /V-oxide strategy by using it not only to form the biaryl carbon-carbon bond, but also to form the C4 carbon-nitrogen bond. Diaryl ether 3, prepared by a copper catalyzed cross-coupling of 4-fluorophenol and l-bromo-4-iodobenzene [83], was coupled... 

Peroxidase catalyzed the oxidative polymerization of fluorinated phenols, 3- and 4-fluorophenols, and 2,6-difluorophenol in an aqueous organic solvent, yielding fluorine-containing polymers [27]. Elimination of fluorine atom partly took place during the polymerization giving polymers with complicated structures. 

Fluorophenol has been derived in a yield of 67% (60% conversion) by heating a mixture of 2-chlorofluorobenene and cupric oxide with 1M dipotassium... 

Hydroxylation Induced during the Autoxidation of N-benzyl-1,4-dihydronicotinamide. Oxygen was bubbled through the aromatic compound suspended in an aqueous solution of N-benzyl-l,4-dihydronico-tinamide and ferric chloride. Four compounds were oxidized by this model system benzene to phenol and no biphenyl toluene to benzyl alcohol, cresols, phenol, and no bibenzyl anisole to phenol and methoxyphenols fluorobenzene to phenol and fluorophenols. Even under optimum... 

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