Fluorination cyclohexane

Nitrogen dioxide Cyclohexane, fluorine, formaldehyde, alcohols, nitrobenzene, petroleum, toluene... 

EXPLOSION and FIRE CONCERNS not flammable NFPA rating Health 3, Flammability 0, Reactivity 1 enhances combustion of organic matter and other combustible materials reacts violently with cyclohexane, fluorine, formaldehyde, and alcohols violent reaction with nitrobenzene, petroleum and toluene poisonous gases may be produced in fire decomposition emits toxic fumes of oxides of nitrogen use water spray or other suitable agent for firefighting purposes. 

Of alicyclic compounds, fluorination of cyclopentane and cyclohexane has been sufficiently investigated in the past. Cycloheptane on fluorination with cobalt trifluoride gives a mixture of highly fluorinated and perfluorinated cycloheptanes and methylcyclohexanes [/2] (equation 12). 

Several reagents are compared in their ability to fluorinate adamantane [2 42, 43, 44, 45, 46 47, 48 (equation 22) Cyclohexane behaves in a similar fashion but gives lower yields [3, 42, 49 ... 

Fluorination of pyridine (90TL775), uracil (90T3093), and octaethyl-porphyrin [88JCS(P1)1735] has been described using cesium fluorooxysulfate. The outcome of the former was strongly dependent on the solvent. For example, with pyridine in methanol no fluorination was observed and 2-methoxypyridine was obtained. 2-Fluoropyridine was isolated when cyclohexane was the solvent (90TL775). 

The Balz-Schiemann reaction continues to attract attention, with much of it generated by the interest in fluoroquinolones, e.g., (7), which is a potential antibacterial. Two approaches to its synthesis are possible—introduction of fluorine prior to or post ring construction. Decomposition of the tetrafluoroborate salt was unsuccessful, whereas the PF6 salt (8) gave only a poor yield (84JMC292). A more successful approach was the introduction of F into the pyridine nucleus prior to formation of the 1,8-naphthyridine ring (84JHC673). A comparison of decomposition media showed that cyclohexane was the best with regard to yield and time. 

In terms of its steric impact, fluorine is the smallest substituent that can replace a hydrogen in a molecule, other than an isotope of hydrogen. Table 1.1 provides insight as to the comparative steric impact of various fluorinated substituents on the equilibrium between axial and equatorial substitution in cyclohexane.14... 

We now focus on the effect of replacing fluorine by another halogen of a higher period, e.g. Br. The trans and cis conformations of 1,2-dibromo-cyclohexane are shown below along with the dominant orbital interactions ... 

Cyanogen chloride Cyclohexane Diethyl ether Dimethyl formaldehyde Dimethyl sulfate Dimethyl sulfide Epichlorohydrin Ethyl acetate Ethyl benzene Ethylene glycol Fluorine... 

Cyclohexane is more environmentally acceptable than the more commonly-used CCl. A recent cleavage of a mono-fluorinated alkene to a ketone was thus effected. The alkene (70 mg, 0.28 mmol) was dissolved in a mixture of acetonitrile (0.5 cm ) and cyclohexane (0.5 cm ) and treated with RuClj.nH O (0.05 g, 0.2 mmol) and Na(lO ) (0.24 g, 10 mmol) in water (1 cm ). The mixture was stirred for 1.5 h, the product extracted with diethylether and dried over MgSO [330]. Other examples, using RuCyaq. 10(0H)j/CgHj2-CH3CN have been given [216]. 

Our fluorous silica technology was also tested (1) on the catalytic hydrogenation of styrene. The fluorous silica phase contained a fluorinated version of Wilkinson s catalyst (Figure 3) deposited onto the surface of the fluorous silica. The organic phase consisted of styrene dissolved in cyclohexane. No fluorous solvent was used. 

Phloroglucinol, which is regarded as the tri-enol form of cyclohexane-1,3,5-trione, gives the hexahydrate of the corresponding perfluoro-trione upon fluorination in formic acid (Fig. 31) [93] (see 3.1.1.2 for a discussion of the fluorination of carbonyl compounds). 

Unsaturated carbon structures usually undergo addition of fluorine, but are vulnerable to fragmentation unless fluorine addition is carefully controlled. Aromatic rings saturate, but polymerization may be a serious side reaction. Many heteroaromatic molecules polymerize giving principally tars and oils. In contrast to the cobalt(III) fluoride process, benzene produces a significantly lower yield of perfluorocyclohexanc than does cyclohexane. 

Selective bromine-fluorine exchange of one bromine atom occurs in the reaction of tram-4,5-dibromo-m-cyclohexane-1.2-dicarboxylic anhydride (10) with sulfur tetrafluoride to give isomers of 5-bromo-l,l,3.3,7-pentafluoro-c/.v-octahydroisobenzofuran (11) and 4-bromo-5-fluoro-m-1.2-bis(trifluoromethyl)cyclohexane (12) in a 5 1 ratio and good total yield.11... 

The fluorination of cyclohexane probably takes place via an initial conversion into benzene, brought about by the fluorinating agent, as under certain conditions (CeF4 at 300 C, a temperature at which benzene does not fluorinate over this reagent) benzene can be isolated as the near-sole product.42 If cyclohexane is first converted into benzene, then all fluorinations of saturated compounds might also proceed via an initial desaturation step this point is touched on several times throughout Section 25.1. The products are much the same as those obtained from benzene (Section 25.1.1.2.). 

Potassium tetrafluorocobaltate(III) at 200°C reacts with tetrahydrofuran to give82 unsaturated products the major ones are 5 and 6, although the overall yield is poor (< 30%). Furan itself gives no products at all over cobalt(IIl) fluoride it presumably polymerizes. This does not, however, rule furan out as an intermediate in the tetrahydrofuran fluorinations (it could form by desaturation, as does benzene in the fluorination of cyclohexane, vide supra). 2-Methyl-and 2,5-dimethyltetrahydrofuran83 have also been fluorinated with similar results to tetrahydrofuran. 

There are few reports of the fluorination of aldehydes, although unpublished work in the author s laboratory has shown that they give rise to two types of product, polyfluoro acid fluorides, in which the carbaldehyde group is converted into the carbonyl fluoride group, and polyfluorohydrocarbons, in which the carbaldehyde group is lost. Pentafluorobenzaldehyde and cobalt(III) fluoride at 135°C afford undecafluorocyclohexanecarbonyl fluoride and nona-fluorocyclohex-3-enecarbonyl fluoride with small amounts of perfluorocyclohexane and methyl-cyclohexane.121... 

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