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Methanesulfenyl bromide

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. [Pg.154]

Thioglycosides can be activated for glycosylation reactions with sulfur electrophiles, e.g., with dimethylfmethylthio)sulfonium triflate or with methanesulfenyl bromide and silverfl + ) to form reactive sulfonium intermediates (F. Dasgupta, 1988). [Pg.271]

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. [Pg.154]

DMSO or other sulfoxides react with trimethylchlorosilanes (TCS) 14 or trimefhylsilyl bromide 16, via 789, to give the Sila-Pummerer product 1275. Rearrangement of 789 and further reaction with TCS 14 affords, with elimination of HMDSO 7 and via 1276 and 1277, methanesulfenyl chloride 1278, which is also accessible by chlorination of dimethyldisulfide, by treatment of DMSO with Me2SiCl2 48, with formation of silicon oil 56, or by reaction of DMSO with oxalyl chloride, whereupon CO and CO2 is evolved (cf also Section 8.2.2). On heating equimolar amounts of primary or secondary alcohols with DMSO and TCS 14 in benzene, formaldehyde acetals are formed in 76-96% yield [67]. Thus reaction of -butanol with DMSO and TCS 14 gives, via intermediate 1275 and the mixed acetal 1279, formaldehyde di-n-butyl acetal 1280 in 81% yield and methyl mercaptan (Scheme 8.26). Most importantly, use of DMSO-Dg furnishes acetals in which the 0,0 -methylene group is deuter-ated. Benzyl alcohol, however, affords, under these reaction conditions, 93% diben-zyl ether 1817 and no acetal [67]. [Pg.201]

This synthesis of sulfenyl chlorides can also be used in the aliphatic series although here the limitation applies that most alkylsulfur halides are too unstable to be isolated from solution. In general, and also in the aromatic series, sulfenyl chlorides are easier to prepare than the bromides, whilst the iodides are known only in a few cases and the fluorides not at all. As an example, Schneider,665 chlorinating methanethiol in anhydrous carbon tetrachloride at —15°, obtained dimethyl disulfide dichloride [chloro(methyl)(methylthio)-sulfonium chloride] which passed into methanesulfenyl chloride when allowed to warm slowly to room temperature ... [Pg.675]


See other pages where Methanesulfenyl bromide is mentioned: [Pg.223]    [Pg.179]    [Pg.214]    [Pg.223]    [Pg.179]    [Pg.214]    [Pg.177]    [Pg.264]    [Pg.177]    [Pg.177]    [Pg.177]   


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