Fluorine compounds, aliphatic tables

This topic has been reviewed [2, pp 94, 100-111, 130-134] All of the standard approaches to the synthesis of a compound like methyl 2-fluorostearate from methyl 2-bromostearate result mall yield of the 2-fluoro ester and the unsaturated esters. Although silver fluoride is not a new reagent, its use moist in wet acetonitrile to convert methyl 2-bromostearate to its fluoro ester is a departure from the traditional set of anhydrous conditions (Procedure 6, p 194) [71] In contrast, silver tetrafluoroborate converts a-chloroketones to their respective fluoroketones under anhydrous conditions. The displacement of less activated halogen groups by silver tetrafluoroborate to form their respective fluorides is novel Although silver tetrafluoroborate could not be used to convert an aliphatic terminal dichloromethyl or trichloromethyl group to its corresponding fluoro derivative, it is an effective fluorine source in other situations [72] (Table 8)... 

In the case of fluorinated molecules, it is important to differentiate the lipophilic character from the hydrophobic character. Both these characters are in tune for nonfluorinated molecules, but they diverge when the number of fluorine atoms increases in a molecule. It is generally recognized that fluorination induces an increase in the lipophilicity. However, this has only been demonstrated for aromatic compounds, and more specifically when fluorine atoms are in the a position of atoms, or groups bearing n electrons (Table 1.8)." Conversely, the presence of fluorine atoms in an aliphatic molecule provokes a decrease in the lipophilicity, while it can enhance the hydrophobicity. This phenomenon is so important that highly fluorinated molecules are not soluble in organic solvents or in water and constitute a third phase. 

While aromatic amines are discussed in Section 5.2.14., various data for aliphatic amines are listed in Table 20. It is worthwhile remembering that tertiary perfluorinated amines, such as perfluorotributylamine. are completely stable, inert and nontoxic compounds, while some partially fluorinated tertiary amines tend to be unstable, eliminating hydrogen fluoride even at low temperature and are therefore toxie. Primary and secondary aliphatic fluorinated amines carrying CF,N groups have not, so far, been isolated due to their instability. 

Flexible aliphatic compounds are also selectively fluorinated. Such substrates may be alkanes, alcohols, carboxylic acid derivatives or ketones as long as the electron-withdrawing group is far enough from the reacting center (Table 2).44 There are differences in yields and reaction rates which are qualitatively easily understood and are directly related to the electron density of the reactive C —H bond. 

The same assay was carried out for five semi-synthetic quassinoids, which were obtained by esterification of the C-15 OH group of desacetyl-isobrucein-B (124) as shown in Table 13. All ester derivatives showed higher antitumor promoting activity than that of the starting quassinoid, desacetyl-isobrucein-B (124). A compound containing a fluorinated aliphatic ester showed the highest potency [36]. 

More than a third part of all the described principal syntheses of pyrimidines bearing fluorinated alkyl at C-4 atom commences from fluorinated p-dicarbonyl compounds 699. The chemistry of these bis-electrophiles was reviewed recently [411, 412] therefore, their preparation is not discussed herein. This synthesis of pyrimidines is fairly general (Table 34) it allows for introducing aliphatic, alicyclic and aromatic p-diketones (Entries 1-10), p-ketoesters (Entries 11-16), and cyclic P-ketoamides (Entry 17). Presence of some functional groups, such as additional ester moiety (Entry 15), is more or less tolerated, whereas increasing steric hindrance results in lowered yields of the products (Entry 10). A scope of conunon NCN binucleophiles include amidines (Entries 1, 11, 12, 17), (thio)urea and its derivatives (Entries 2-4), guanidines (Entries 5,16) and biguanides (Entry 6). Electron-rich amino heterocycles e.g. aminoazoles and even 2,6-diaminopyridine) are excellent NCN binucleophiles for the principal synthesis of fused pyrimidine derivatives (Entries 7-10, 13-15). 

Public concern over the possible effects of chemicals on man and his environment has largely focussed on a small number of classes of compounds of these, chlorinated hydrocarbons are perhaps the best known. A cursory examination of the scientific literature could easily lead to the impression that they consist entirely of chlorinated pesticides and polychlorinated biphenyls but in terms of total quantity produced, these are less important than many others. This Chapter discusses another class, the aliphatic and C2 Halocarbons, which includes most of the halogenated products of the Organic Chemicals industry, which are of major commercial importance. (Table 1) it excludes all those containing Fluorine. 

---