Fluorine displacement

N-fluorine displacement, 7, 272 1-Azetine, 2-alkoxy-nucleophilic reactions, 7, 271 1-Azetine, 2-aryl-mass spectrometry, 7, 268 nucleophilic reactions, 7, 271 1-Azetine, 2-chIoro-nucleophilic reactions, 7, 271... 

Primary alkyl chlorides are fairly stable to fluorine displacement. When fluorinated, 1-chloropropane is converted to 1-chloroheptafluoropropane and 1-chloto-2-methylbutane produces 39% l-chlorononafluoro-2-methylbutane and 19% perfluoro-2-methylbutane. Secondary and tertiary alkyl chlorides can undergo 1,2-chlorine shifts to afford perfluonnated primary alkyl chlorides 2-Chloro-2-methylpropane gives l-chlorononafluoro-2-methylpropane, and three products are obtained by the fluorination of 3-chloropentane [7] (equation 1). Aerosol fluorina-tion of dichloromethane produces dichlorodifluoromethane which is isolated in 98% purity [4 (equation 2). If the molecule contains only carbon and halogens, the picture is different. Molecular beam analysis has shown that the reaction of fluorine with carbon tetrachlonde, lodotrichloromethane, or bromotrichloromethane proceeds first by abstraction of halogen to form a trichloromethyl radical [5]... 

Nucleophilic fluorination is particularly useful in the synthesis of 2-fluoro-2-deoxypyranoses (e.g., DAST fluorination, displacement of a leaving group by a fluoride ion, oxirane ring opening with HF-amine complexes). Electrophilic fluorination also allows the synthesis of 2-fluoro-2-deoxypyranoses. 

Then, nucleophilic aromatic substitution was applied for the synthesis of l,2,4,6,7,9-hexafluoro-l,4-dibenzodioxin from 2,3,4,6-tetrafluorophenol in the presence of sodium /-butylate <1995JFC(73)265>. In a similar way, cyano-1,4-dibenzodioxins and cyano-l,4-dibenzodithiins have been synthesized by fluorine displacement reactions with catechols <2001NJC379, 2001NJC385>. In accordance with a similar mechanism, the synthesis of spiro (l,4-benzodioxin-2,4 -piperidines) 205 and spiro (l,4-benzodioxin-2,3 -pyrrolidines) 206 have been developed from alcohols 207 and 208, respectively, both of them being obtained from 2-fluorophenol 210 with the corresponding epoxide 209 (Scheme 18) <2003SL813>. 

We have therefore deduced from the formula for the heat of formation of ionic compounds the important rule that the halogens replace one another in the order F2, Cl2, Br2, I2. There are ho known exceptions to this rule. Fluorine displaces chlorine, bromine and iodine from all chlorides, bromides and iodides, while chlorine and bromine displace iodine from all iodides. It is to be expected that the same substitution reactions can take place with the chal-cogens 02, S, Se and Te, and, since the heat of formation of the oxides is, as a rule, greater than that of the sulphides, the reactions of the type... 

Our approach was based on the observation that it is possible to perform SwAr reactions on solid support with amino acids using a solvent system comprised, in equal parts, of acetone and an aqueous 0.5 M NaHC03 solution at temperatures around 70-75°C. Application of this solvent system to the synthesis of quinoxalin-2-ones 6 from la and a-amino acids is described in Section 3.3.2. With respect to the synthesis of 1,5-ben-zodiazepin-2-ones 4, more than 40 examples of aliphatic and aromatic P-amino acids 35 were found to furnish the desired o-nitro anilines 36, about 80% of which were successfully carried on to eventually afford the ben-zodiazepinone products 4 (Scheme 6). In general, the anthranilic acids required slightly harsher conditions to drive the fluorine displacement to completion (75-80°C, 72 h vs. 70-75°C, 24 h for aliphatic P-amino acids). 

The combination of a hydrogen fluoride addition and a chlorine-fluorine displacement converts 1,1 2,2-tetrachloroethylene-l,2 di(isocyanidedichlonde)to perfluoro-iV./V-dimethylethylenediamine [37] (equation 28)... 

Perfluoropyridme gives the usual replacement of the 4-fluonne on reactions with either aromatic or aliphatic mercaptides [55, 56] The reaction of perfluoropyridme with cesium tnfluoromethyl mercaptide, generated from thiocarbonyl fluoride and cesium fluoride, shows temperature dependence of selectivity in fluorine displacement [55 56] (equation 24)... 

Some of the more important commercial uses involve fluorine displacement lo yield chlorofluoromethane refrigerants, such as Irichlorofluoromethane (R-l I) and dichlorodifluoromethane (R-12). 

The rate of fluorine displacement from fluorotoluenes by H-atoms has been measured in single-pulse shock tubes at 988-114 K.158 The addition of CF3 to CgFsCl has been studied.159 The intermediate adduct radical (CF3C6F5C1) was shown to react with an additional CF3 to give CF3CI and C6F5CF3. A range of fluorinated biphenyls can be produced by the reaction of pentafluorobenzene radicals with both electron-rich and -poor aromatics. The isomeric ratios of biphenyls produced indicated an efficient homolytic chain process.160... 

A number of OH group-terminated SWCNTs have been prepared by fluorine displacement reactions of F-SWCNTs with a series of diols and glycerol in the presence of alkali or with amino alcohols in the presence of pyridine as catalyst... 

The groups obtained by fluorine displacement are different from Grimm s pseudoelements, being neither isoelectronic nor isoprotonic with their reference atoms and should conceptually be clearly differentiated from them. It is suitable to call these and other radicals obtained similarly paraelements.3... 

In boron trifluoride adducts, fluorine displacement is relatively difficult and, thus, the widest range of adducts has been prepared for the trifluoride (66,120). As fluorine is replaced by successively heavier halogens the displacement of halogen occurs more readily and secondary reactions of the initially formed donor-acceptor adducts... 

The reagent triethylamine bishydrofluoride, which is prepared by mixing two equivalents of the known and stable reagent triethylamine trishydrolluoride with one equivalent of triethylamine, was recently introdueed as a new, efficient reagent for nucleophilic fluorine displacement reactions. Its nucleophilic power is even greater than that of triethylamine trishy-drofluoride, as can be seen from the reaction of 3. ... 

A number of protein structures determined by X-ray crystallography have been reported to date for the complexes of various enzymes with fluorine-containing substrate mimics or inhibitors bearing multiple fluorines. This strongly suggests that not only single fluorine displacement but also various fluorine-substitution patterns in substrate analogues... 

This is precisely the set of fluorine displacements that we constructed in Sect. 4.8 in order to describe the vibrational modes of UFe. One remarkable result of induction theory is that the mechanical representation can also be obtained as the direct product of the positional representation and the translational representation, T u, this is the representation of the three displacements of the centre of the cluster. 

Polymerization was carried out via the one-pot method, but selective fluorine displacement was sequentially followed by nitro displacement. Fluorine displacement of 5-fluoro-2-nitrobenzotrifluoride with l,l,l-tm(4-hydroxyphenyl)ethane was carried out in DMSO at 80 °C for 4h in the presence of K2CO3, and then the reaction mixture was subjected to the nitro displacement reaction at 170°C for 6h. The polymerization proceeded homogeneously without gelation or precipitation at a concentration of lOwt.% monomers. Both A3+BC and A2C polymerization at a higher monomer concentration (25 wt.%) produced a gel. 

Scheme 2.17 Synthesis of hb poly(arylene ether)s from monomers containing nitro group (a) via selective and sequential S vjAr (preferential fluorine displacement followed by nitro displacement) reaction of As-and BC-type monomers (b) via nitro displacement reaction of A2C-type monomer. Taken from Ref. [76],...

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