Sulfonium fluoride

Beurskens PT, Jeffrey GA (1964) Polyhedral clathrate hydrates VII. Structure of the monoclinic form of the tri-n-butyl sulfonium fluoride hydrate. J Chem Phys 40 2800-2810... 

I l.C Tri - n - butyl sulfonium fluoride hydrate (monoclinic form)... 

A stereoconvergent reaction without any correlation between the geometry of the enolate and simple diastereoselectivity occurs when fluoride ions are used to induce an aldol addition of enolsilanes to aldehydes. For example, both a 99 1 and a 9 91 mixture of the following (Z)/( )-enolsilane lead predominantly to the formation of the. un-adduct in a highly selective manner, when the addition is mediated by tris(diethylamino)sulfonium difluorotrimethylsili-conate27,28. 

Fluoride ion can also induce reaction of silyl ketene acetals with electrophilic alkenes. The fluoride source in these reactions is fnT-(dimethylamino)sulfonium diflu-orotrimethylsilicate (TASF). 

It was found that treatment of a mixture of 120 and 121 with tris(diethylamino-sulfonium) trimethyldifluorosilicate [TASF(Et)] resulted in smooth addition-elimination to the naphthoquinone to form the y-alkylation product 125 (85 %). TASF(Et) is a convenient source of soluble, anhydrous fluoride ion [47]. It is believed that exposure of 121 to TASF(Et) results in fluoride transfer to generate a hypervalent silicate anion, as depicted in structure 124. The transfer of fluoride between TASF(Et) and 121 may be driven by stabilization of the anionic species 124 by delocalization of the carbon-silicon bond into the LUMO of the unsaturated ketone. 1,4-Addition-elimination of this species to the naphthoquinone 120 would then form the observed product. 

Fluoride ion catalyzes the hydrosilylation of both alkyl and aryl aldehydes to silyl ethers that can be easily hydrolyzed to the free alcohols by treatment with 1 M hydrogen chloride in methanol.320 The most effective sources of fluoride are TBAF and tris(diethylamino)sulfonium difluorotrimethylsilicate (TASF). Somewhat less effective are CsF and KF. Solvent effects are marked. The reactions are facilitated in polar, aprotic solvents such as hexamethylphosphortriamide (HMPA) or 1,3-dimethyl-3,4,5,6-tetrahydro-2(l //)-pyrirnidinone (DMPU), go moderately well in dimethylformamide, but do not proceed well in either tetrahydrofuran or dichloromethane. The solvent effects are dramatically illustrated in the reaction of undecanal and dimethylphenylsilane to produce undecyloxyphenyldimethylsi-lane. After one hour at room temperature with TBAF as the source of fluoride and a 10 mol% excess of silane, yields of 91% in HMPA, 89% in DMPU, 56% in dimethylformamide, 9% in tetrahydrofuran, and only 1% in dichloromethane are obtained (Eq. 164).320... 

Analyses were performed on each of the resist components to determine the source of the background acid. Background acid was present in all three resist components — polymer, sulfonium salt, and casting solvent. However the sulfonium salt contained the highest concentration of acid by two orders of magnitude. Residual acid in sulfonium salt may be due to the method of preparation which involves an aqueous metathesis step to exchange the hexafluoroantimonate ion for bisulfate. This procedure is likely to produce hydrogen fluoride due to hydrolysis of hexafluoroantimonate salt (14). 

Sulfenyl fluorides are extremely unstable and therefore only few perhalosulfenyl fluorides have so far been reported122. The formal addition of the elements of methanesulfenyl fluoride to carbon-carbon double bonds has been obtained123 by a one-pot reaction with dimethyl(methylthio)sulfonium tetrafluoroborate and triethylammonium tris(hydrofluo-ride). With this system also the addition to double bonds is highly stereoselective, at least... 

Finally, in contrast to the reactions reported above, 49 reacts131 with dimethyl(methyl-thio)sulfonium fluoroborate (DMTSF) and triethylamine tris(hydrofluoride) in dichlorome-thane to give only 5% of the 1,2-addition product 122. The main products, present in 73 27 ratio, are the exo-exo and endo-exo adducts 123 and 124, formed by exclusive exo attack of the electrophile on the double bond, followed by transannular -participation in the intermediate bridged cation and final addition of fluoride to the nortricyclic cation from both the exo or endo side (equation 120). 

The selective introduction of fluorine is of continuing interest not only because of the synthetic challenge but also because of the possibility of a dramatic change in biological activity. The fluoride-ion displacement of carbohydrate trifluoromethanesulfonates using tris(dimethylamino)sulfonium... 

Group transfer polymerization (GTP) requires either a nucleophilic or Lewis acid catalyst. Bifluoride (HF2) and fluoride ions, supplied by soluble reagents such as tris(dimethylamino)-sulfonium bifluoride, [(CH3)2N]3SHF2, and (w-C NF, are the most effective nucleophilic catalysts, although other nucleophiles (CN , acetate, p-nitrophenolate) are also useful. Zinc... 

Tris(dimethylam1no)sulfonium difluorotrimethylsilicate is a source of soluble organic fluoride ion of high anionic reactivity. Fluoride ion from this salt and other tris(dialkylamino)sulfonium difluorotrimethyl si 11 cates has... 

Tris(dialkylamino)sulfonium difluorotrimethylsilicates are very hygroscopic solids and great care must be taken to work under strictly anhydrous conditions. They are not sufficiently reactive to fluorinate carbonyl compounds or even alcohols. However, they are very soluble in organic solvents and are useful sources of unsolvated fluoride ion. The most commonly used reagent is the commercially available TASF. 

Tris(dialkylamino)sulfonium difluorotrimethylsilicates can convert halides to their corresponding fluorides under mild conditions, e.g. 3 to 4. 

Although tris(dialkylamino)sulfonium difluorotrimethylsilicates are not sufficiently reactive to fluorinate alcohols, they are able to convert trifluoromethanesulfonates to their corresponding fluorides under mild conditions. The mild conditions required to form the ester and to perform the fluorination step, has resulted in TASF (1) and related reagents finding wide application in the syntheses of fluorinated carbohydrates (see Table 10).5"76-78 It is of interest that this process is a modern development of the first reaction ever used to synthesize an organic fluoride in 1835 (see Introduction 1.2.). 

Super anions. Unlike quaternary ammonium fluorides, 1 can be obtained anhydrous, li reacts with enol silyl ethers to form an unsolvated tris(diethylamino)-sulfonium (TAS) enolate in which there is negligible interaction hetween the ions.3 The naked enolate undergoes C-alkylation at —78 to — 30°. ... 

ALDOL CONDENSATION Cesium fluoride. Dialkylboron trifluoromethane-sulfonates. Dichlorobis(cyclopentadi-enyl)zirconium. Diisobutylaluminum phenoxide. 2,5-Dimethylphenylpropi-onate. DimetIiyl(phenyllhio)aIuminum. Lithium iodide. Triethylborane. Tri-methylsilyl trifluoromethanesulfonate. Triphenyltin chloride. TrisCdiethyI-amino)sulfonium difluorotrimethyl-siliconate. 

Fluorine and sulfur (in the form of a methylthio group) are added to nucleophilic olefins with Markovmkov regioselectivity and anti stereoselectivity by di-methyl(methylthio)sulfonium fluoroborate and triethylamine tris(hydrogen fluoride) [177] (equation 21)... 

Tris(dimethylamino)sulfonium difluo-rotrimethylsilicate, 336 Xenon(II) fluoride, 345 Alkyl bromides Potassium permanganate, 258 Sodium bromide, 46 Tetraethylammonium bromide, 46 Alkyl iodides Aluminum iodide, 17 Potassium permanganate, 258 Sodium iodide, 46 Tetraethylammonium iodide, 46 Alkynes (see also Acetylenic carbonyl compounds, Diynes, Enynes, Propar-gyl alcohols)... 

Addition of a sulfenyl chloride to an alkene in the presence of silver fluoride affords (3-fluoro sulfides, as shown in equation (2).18 The same trans adducts can also be prepared from the sulfenyl chloride adducts and silver fluoride. An alternative procedure for the formal addition of methanesulfenyl fluoride to alkenes involves the use of dimethyl(methylthio)sulfonium tetrafluoroborate and triethylamine tris(hy-drofluoride) as in equation (3).19... 

NMO NMP Nu PPA PCC PDC phen Phth PPE PPTS Red-Al SEM Sia2BH TAS TBAF TBDMS TBDMS-C1 TBHP TCE TCNE TES Tf TFA TFAA THF THP TIPBS-C1 TIPS-C1 TMEDA TMS TMS-C1 TMS-CN Tol TosMIC TPP Tr Ts TTFA TTN N-methylmorpholine N-oxide jV-methyl-2-pyrrolidone nucleophile polyphosphoric acid pyridinium chlorochromate pyridinium dichromate 1,10-phenanthroline phthaloyl polyphosphate ester pyridinium p-toluenesulfonate sodium bis(methoxyethoxy)aluminum dihydride (3-trimethylsilylethoxy methyl disiamylborane tris(diethylamino)sulfonium tetra-n-butylammonium fluoride f-butyldimethylsilyl f-butyldimethylsilyl chloride f-butyl hydroperoxide 2,2,2-trichloroethanol tetracyanoethylene triethylsilyl triflyl (trifluoromethanesulfonyl) trifluoroacetic acid trifluoroacetic anhydride tetrahydrofuran tetrahydropyranyl 2,4,6-triisopropylbenzenesulfonyl chloride 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane tetramethylethylenediamine [ 1,2-bis(dimethylamino)ethane] trimethylsilyl trimethylsilyl chloride trimethylsilyl cyanide tolyl tosylmethyl isocyanide meso-tetraphenylporphyrin trityl (triphenylmethyl) tosyl (p-toluenesulfonyl) thallium trifluoroacetate thallium(III) nitrate... 

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