Diphenyl sulfonium tetrafluoroborate

Several examples of the alkylation of sulfur ylides are known. " " This reaction is particularly useful for the synthesis of j-alkyl diphenylsulfonium salts which cannot otherwise be prepared from diphenyl sulfide, 5-alkyl iodides and silver tetrafluoroborate, since the latter reaction usually leads to a mixture of regioisomeric sulfonium salts. Diphenylsulfonium methanide on reaction with [ C]methyl iodide allows the synthesis of [ C]isopropyl diphenyl sulfonium salt which has been used for the synthesis of [ C]-2,3-epoxysqualene (Scheme 130, entry a). This reaction unfortunately is not general... 

Among the several examples given, the reaction of ( )-(55,67 )-4-rert-butoxycarbonyl-3-ethylidene-5,6-diphenyl-3,4,5,6-tetrahydro-2//-morpholin-2-one (20) with the ylide from racemic (diethylamino)(methyl)(oxo)(phenyl)sulfonium tetrafluoroborate to give the cyclopropane derivative 21 in 82% yield with 100% diastereofacial selectivitycan be mentioned. 

Related Reagents. 1-Benzenesulfinyl Piperidine Dimethyl (Methylthio)sulfonium Tetrafluoroborate W-Iodosuccinimide Diphenyl Sulfoxide. 

Related Reagents. Methyl Iodide Methyl Sulfate 1-Benzene-sulfinyl Piperidine Diphenyl Sulfoxide Dimethyl(methylthio) Sulfonium Tetrafluoroborate. 

The cationic polymerization of styrene sulfide has been reinvestigated by Van Craeynest (15). With triethyloxonium tetrafluoroborate as initiator, a rapid and quantitative polymerization was observed, followed by a slow degradation of die polymer to a mixture of cis and tram 2,5-diphenyl-l, 4-dithiane and as and tram 2,6-diphenyl-1,4-dithiane. Since the BF4 counter ion is not capable of forming a covalent bond, a back-biting reaction via sulfonium ions seems the plausible mechanism for the dimer formation. The polymerization initiated with dimethyl sulfate showed the same characteristics a fast polymerization is followed by degradation to the same mixture of isomeric diphenyl- 1,4-dithianes. However, the mwts-2,5-diphenyl derivative was the only isomer that crystallized from the solution. It is therefore reasonable to accept that with dimethyl sulfate also, the cyclic dimers of styrene sulfide are formed by a back-biting type of degradation of the polymer and not by the mechanism shown above. 

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