Fluorides carbon—sulfur bonds

In 1998, Harmata and co-workers <98T9995> published a new synthesis of 2-alkenyl anilines. The silylated 2,1-benzothiazines 187 could be deprotonated by n-BuLi and alkylated by different electrophiles. The corresponding products could be desilylated by fluoride with concomitant cleavage of the carbon-sulfur bond to give 2-alkenylsulfinanilides that can then be hydrolyzed by base to the anilines 195 in good yields (Scheme 55). 

Fluorine/iodine mixtures, which can be regarded as sources of both iodonium and fluoride ion, have been used to prepare glycosyl fluorides from the corresponding thioglycosides and gem-difluorides from some diaryl-1,3-dithio-lanes (Fig. 68) [161,162]. Activation of the carbon-sulfur bond towards nucleophilic attack by fluoride ion is achieved by complexation of the thiophilic iodonium species with the sulfur atoms. 

Catalysis. Catalytic properties of the activated carbon surface are useful in both inorganic and organic synthesis. For example, the fumigant sulfuryl fluoride is made by reaction of sulfur dioxide with hydrogen fluoride and fluorine over activated carbon (114). Activated carbon also catalyzes the addition of halogens across a carbon—carbon double bond in the production of a variety of organic haUdes (85) and is used in the production of phosgene... 

In contrast to phosphorus esters, sulfur esters are usually cleaved at the carbon-oxygen bond with carbon-fluorine bond formation Cleavage of esteri nf methanesulfonic acid, p-toluenesidfonic acid, and especially trifluoromethane-sulfonic acid (tnflic acid) by fluoride ion is the most widely used method for the conversion of hydroxy compounds to fluoro derivatives Potassium fluoride, triethylamine trihydrofluoride, and tetrabutylammonium fluoride are common sources of the fluoride ion For the cleavage of a variety of alkyl mesylates and tosylates with potassium fluoride, polyethylene glycol 400 is a solvent of choice, the yields are limited by solvolysis of the leaving group by the solvent, but this phenomenon is controlled by bulky substituents, either in the sulfonic acid part or in the alcohol part of the ester [42] (equation 29)... 

The chemistry of aromatic alkylation is more complicated than implied by equations (15, 16, 17). Polymerization, CP production, and the isomerization of heavier olefins also occur. Olson (32) has reported many details of the positional isomerization of 1-aIkenes in the Ce—Cm range. Using 1-dodecene as an example, the alkylated product is a mixture of 2- through 6-dodecyl benzenes. In the absence of isomerization, only 2-dodecyl benzene is produced. Attachment at the first carbon atom is not expected when propylene or heavier olefins are employed since primary cations would then be obtained. Secondary cations are however more stable (or preferred) and lead to the attachment at the second or higher carbon atom of the cation. Olson suggests that positional isomerization involves the formation of dodecyl acid sulfates or dodecyl fluorides when sulfuric acid or HF are used as catalysts reverse reactions then lead to the formation of olefins with double bonds in a new position on the chain. In one example reported, at least 80% of the dodecene isomerized before alkylation (by reactions similar to eqs. 16 and 17). Olson also found that some of the initial dodecylbenzene produced were isomerized. The 2-dodecyl benzene that was initially produced isomerized in the presence of AICI3 catalysts to give from 3-dodecyl to 6-dodecyl benzenes. 

The by-products formed are shorter-chain sulfonyl fluorides or chlorides and fluorocarbons [51-54]. The structures of the by-products suggest a cleavage of carbon-sulfur and carbon-carbon bonds and some oxidative degradation as well. 

Unsaturated fluorinated compounds are fundamentally different from those of hydrocarbon chemistry. Whereas conventional alkenes are electron rich at the double bond, fluoroal-kenes suffer from a deficiency of electrons due to the negative inductive effect. Therefore, fluoroalkenes react smoothly in a very typical way with oxygen, sulfur, nitrogen and carbon nucleophiles.31 Usually, the reaction path of the addition or addition-elimination reaction goes through an intermediate carbanion. The reaction conditions decide whether the product is saturated or unsaturated and if vinylic or allylic substitution is required. Highly branched fluoroalkenes, obtained from the fluoride-initiated ionic oligomerization of tetrafluoroethene or hexafluoropropene, are different and more complex in their reactions and reactivities. 

Solution The first two ions are single atom anions and are called sulfide and nitride. The next two are binary ionic compounds, calcium fluoride and potassium sulfide. The polyatomic ions hydroxide and sulfate are present in sodium hydroxide and sodium sulfate. Finally, the last two compounds are covalently bonded and are called sulfur trioxide and carbon tetrachloride. 

Conjunct Polymer Formation The polymers (also called acid-soluble oils or red oil) dissolve in the acid phase (sulfuric acid and HP). They have a hydrogen/ carbon atomic ratio (H/C) of about 1.75 and a molecular weight of 270-325. ° They contain numerous -C=C-bonds, which react to a significant extent with sulfuric acid to produce conjimct acid sulfates or with HP, conjunct polymer fluorides. These sulfates (or fluorides)... 

The perfluorethyl and -isopropyl derivatives readily deconq)ose. Possible deconq)osition mechanisms are fi-fluoride transfer from carbon to sulfur under formation of perfluoroalkenes and SF5" or heterolytic cleavage of the C-S bond to give Rp" and SF4 as the primary products (26). 

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