Sulfuranes

MO calculations for the gas phase indicate that sulfurane intermediate (17) is more stable than the ion (18) by about 380 kJ moP, which suggests that sulfuranes may be important in the reaction of sulfenyl halides with alkenes in non-polar solvents (77JCS(P2)1019). 

S-Alkylthiiranium salts, e.g. (46), may be desulfurized by fluoride, chloride, bromide or iodide ions (Scheme 62) (78CC630). With chloride and bromide ion considerable dealkylation of (46) occurs. In salts less hindered than (46) nucleophilic attack on a ring carbon atom is common. When (46) is treated with bromide ion, only an 18% yield of alkene is obtained (compared to 100% with iodide ion), but the yield is quantitative if the methanesulfenyl bromide is removed by reaction with cyclohexene. Iodide ion has been used most generally. Sulfuranes may be intermediates, although in only one case was NMR evidence observed. Theoretical calculations favor a sulfurane structure (e.g. 17) in the gas phase, but polar solvents are likely to favor the thiiranium salt structure. 

Fluoride ion attacks the sulfur atom in 2,3-diphenylthiirene 1,1-dioxide to give ck-1,2-diphenylethylenesulfonyl fluoride (23%) and diphenylacetylene (35%). Bromide or iodide ion does not react (80JOC2604). Treatment of S-alkylthiirenium salts with chloride ion gives products of carbon attack, but the possibility of sulfur attack followed by addition of the sulfenyl chloride so produced to the alkyne has not been excluded (79MI50600). In fact the methanesulfenyl chloride formed from l-methyl-2,3-di- -butylthiirenium tetrafluoroborate has been trapped by reaction with 2-butyne. A sulfurane intermediate may be indicated by NMR experiments in liquid sulfur dioxide. 

Sulfurane reagent lor conversion of trans diols to epoxides, generally for dehydration of diols to olefins or cyclic ethers, and as an oxidizing agent... 

BIS[2,2,2-TRIFLUORO-l-PHENYL-l-(TEIFLUOROMETHYL) ETHOXY] DIPHENYL SULFURANE... 

B. Bis[2,2,2-trifiuoro-l-phenyl-l- trijlucrromethyl[ethoxy] Diphenyl Sulfurane. Carbon tetrachloride is distilled directly from phosphorous pentoxide into a dry, 2-1., three-necked flask fitted with stoppers until... 

The great reactivity of the sulfurane prepared by this procedure toward active hydrogen compounds, coupled with an indefinite shelf life in the absence of moisture, makes this compound a useful reagent for dehydrations,amide cleavage reactions, epoxide formation, sulfilimine syntheses, and certain oxidations and coupling reactions. 

Synthetic applications of organosulfur reagents are expanding rapidly. Stable sulfuranes are included for the first time in BIS[2,-2,2-TRIPLUORO-l-PHENYL-l-(TRIFLUOROMETHYL)ETHOXY] diphenyl SULFURANE and DIETHYLAMINOSULFUR TRI-FLUORIDE. The latter is used to transform an alcohol to a fluoride in p-NITROBENZYL FLUORIDE. The direct homologation of a ketone to a nitrile by use of p-TOLYLSULFONYLMETHYL ISOCYANIDE is illustrated in 2-ADAMANTANECARBONITRILE. Reagents with... 

Fluonnation with Diethylammosulfur Tnfluonde and Related Aminofluoro sulfuranes... 

When there is an a-hydrogen in the sulfide, the sulfuranes are unstable and cannot be isolated [775]. Sulfoxides [776] and sulfinyl fluorides [777] are oxidatively fluorinated with tluorine to give hexavalent sulfur compounds in yields up to 90%. 

Synthesis and stereochemical study of reactions of optically pure cyclic sulfuranes, S(rV)-derivatives and their Se(IV)- and Te(IV)-analogs 99YGK587. 

Sulfones have been prepared by three principally different strategies One-component methods include various isomerizations, rearrangements under degradation, and hydrolysis of oxygen-substituted dialkyl (diaryl) sulfuranes(VI). 

Oxidative cleavage of oxosulfonium ylides490 as well as of sulfoximines491 leads to sulfone formation. In the course of oxidations of dialkoxy sulfuranes(IV) by hydrogen peroxide492 or f-butyl hydroperoxide493, sulfone formation takes place (equation 99). 

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