A Source of fluorine

Fluorine is widely distributed in nature [1] and it is estimated that, among the elements, fluorine is about thirteenth in abundance. Phosphate rock, which is processed on a multimillion-ton scale as raw material for the fertiliser industry, contains as much as 3.8% of fluorine and is a very rich source of the element. However, the fluorine recovered from this process as fluorosilicic acid is still not a commercially competitive source of fluorine compared with fluorspar (CaF2), although reserves of the latter are said to be limited and it is expected that use of fluoride in phosphate rocks will eventually be increased. 

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HF is used as a source of fluorine for production of all the various fluorocarbon products. HF reacts in the presence of a suitable catalyst and under the appropriate temperature and pressure conditions with various organic chemicals to yield a family of products. A by-product stream of hydrochloric acid may be co-produced. 

An amine with labile fluorine atoms, A -(l,l,2,3,3,3-hexafluoropropyl)diethylamine, generated in situ by the interaction of perfluoroprop-l-ene and diethylamine, was found to work well as a source of fluorine in the reactions of 1,3-dithiolanes with 1,3-dibromo-5,5-dimethylhydan-toin or A -iodosuccinimide. The reactions run in dichloromethane at — 78 to — 20 C give gem-difluorides in 50-70% yield.76... 

Xenon difluoride is able to transfer a fluorine atom to organic molecules without any catalyst, with very reactive organic molecules or at higher temperatures or under photochemical conditions. However, reactions are usually performed in the presence of various types of catalysts, but in some cases a new xenon compound FXeYL is formed (Scheme 1), which can be a source of fluorine atoms, or of a YL or Y group for transfer to an organic molecule. On the other hand, decomposition of the FXeYL molecule results in the desired fluorinated products (FYL, FL or FY). Fluoro-substituted xenon derivatives (FXeYL) can also be further transformed to disubstituted derivatives, which are usually less stable at room temperature, but can also be excellent sources of YL, Y or L groups for transfer to various organic molecules. The next possibility is that xenon difluoride converts an... 

J. Cross couplings of aryl or alkenyl halides with TMSA proceeds in the presence of a Pd catalyst and Cul, followed by treatment with dilute aqueous KOH [54a] or K2CO3 in MeOH or a source of fluorine, such as KF, KF-crown ether, TASF, or Bu4NF to give terminal acetylenes [43a]. 

High grade fluorspar is used for the manufacture of anhydrous hydrofluoric acid. The anhydrous acid is a source of fluorine itself, of the fluorides of many metals, and also of freons such as CFg lg. 

Sodium fluoride is utilized in the manufacture of organofluoro-compounds (halogen exchange reaction), as a preservative, and as a source of fluorine for toothpaste additives (sodium monofluorophosphate). 

Direct fluorination of pyridine can also be carried out using CSSO4F as a source of fluorine. It was shown that pyridine readily reacts with CSSO4F at room temperature producing a mixture of different products (2-fluoro-, 2-fluorosulfonate- and 2-chloro- or 2-aLkoxypyridines). ... 

Fluorspar is used chiefly as a flux material in the smelting of iron and steel. It is also used as a source of fluorine and hydrofluoric acid and in the manufacture of ceramics and in the optical-glass industry. 

MeOH or a source of fluorine, such as KF, KF-crown ether, TASF, or to give... 

Radical-cations may also be involved in the formation of phenyl esters from aromatic carboxylic acids and benzene in the presence of xenon difluoride, and can apparently be detected by e.s.r. spectroscopy during the reaction of iViV-dimethylaniline with perfluoropiperidine. The last reagent gives a low yield of o- and p-fluorophenol in the ratio 3.5 1 in its reaction with sodium phenoxide, and the predominance of ortho substitution is ascribed to a cage mechanism of the type shown in (3). However, towards 2,4,6-tri-t-butylphenoxyl radicals the piperidine acts as a source of fluorine atoms to give the dienone (4). ... 

Gaseous SF3 is a gentle and effective electrophilic monofluorinating reagent for flve-membered heterocyclic compounds. The reaction of thiophenes 1,7 with gaseous SF3, generated by electron ionization of sulfur hexafluoride and acting as a source of fluorine cation (F ), is one more example of a direct fluorination process [12],... 

Another example of flnorine/chlorine exchange selectivity one can find in Novartis patent were chloroflnoropyrimidine 132 react with cyclopentylamine leading to compound 133 (Scheme 29) [152]. It should be noted, that the synthesis of starting compound 131 is similar to approach shown on Scheme 24, where CF3 group is a source of fluorine in pyrimidine nuclear. 

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