5-bromo, reaction with mercaptans

Transformations of various 2-bromo-substituted derivatives of [l,3,4]thiadiazolo[3,2-tf]pyrimidines are shown in Scheme 27. Thus, reaction of 218 with dimethylamine gave 219 in medium yield <2005JHC1105>, treatment of 220 with mercaptans afforded 221 in good yield <1999IZV1154>, whereas reaction of 222 with hetarylamines and hetarylmercaptanes yielded 223 <1993IZV1954, 1994KGS560>. 

The interaction of alkyl halides with mercaptans or alkaline mercaptides prodnces thioalkyl derivatives. This is a typical nncleophilic substitution reaction, and one cannot tell by the nature of products whether or not it proceeds through the ion-radical stage. However, the version of the reaction between 5-bromo-5-nitro-l,3-dioxan and sodium ethylmercaptide can be explained only by the intermediate stage involving electron transfer. As found (Zorin et al. 1983), this reaction in DMSO leads to diethyldisulfide (yield 95%), sodium bromide (quantitative yield), and 5,5 -bis(5-nitro-l,3-dioxanyl) (yield 90%). UV irradiation markedly accelerates this reaction, whereas benzene nitro derivatives decelerate it. The result obtained shows that the process begins with the formation of ethylthiyl radicals and anion-radical of the substrate. Ethylthiyl radicals dimerize (diethyldisulfide is obtained), and anion-radicals of the substrate decompose monomolecularly to give 5-nitro-l,3-dioxa-5-cyclohexyl radicals. The latter radicals recombine and form the final dioxanyl (Scheme 4.4). 

For the determination of alkyl- and arylmercaptans, reaction with acrylonitrile followed by analysis of unreacted excess has been recommended [135]. Atkinson and Natoli [171] proposed an indirect catalytic method. The determination of tertiary and secondary thiols has been discussed [172]. Kawahara [173] proposes to detect trace amounts of mercaptans in the form of pentafluorobenzyl esters prepared from a-bromo-... 

The synthesis of benzo[6]thiophenes by the PPA-promoted cyclization of (arylthio)acetaldehyde dimethyl or diethyl acetals [Eq. (4)] was introduced by Tilak287, 288 in 1950 and improved in 1951.289 The acetals are readily prepared from aryl mercaptans and bromo-acetaldehyde dimethyl (or diethyl) acetal in the presence of sodium ethoxide, or by reaction of an aryllithium compound with [(MeO)2CHCH2S]2.290 Diethyl acetal as starting material sometimes gives better yields of product than the corresponding dimethyl acetal.291 Optimum yields of benzo[6]thiophenes are obtained when cyclization of the acetals is carried out under reduced pressure so that the lower boiling benzo[6]thiophenes distill as soon as they are formed. Experimental conditions for obtaining optimum yields vary from case... 

Gem-dibromocyclopropanes can be converted into synthetically useful cyclopropanone equivalents by a process consisting of lithium-halogen exchange followed by reaction of lithiocyclopropane (113) with dimethyl disulfide (Scheme 43) . The resulting bromo-methylthio derivative (114) undergoes a variety of substitution reactions. Methanolysis gives S,0-dimethylketal (115) which can be converted into l,l bis(methyl-thio)cyclopropane (116) with methyl mercaptan in trifluoroacetic acid. Reaction of 114 with other nucleophiles provides the derivatives shown in Scheme 44 . The sulfur-... 

Four ethylthiocodides have been reported to exist. a-Ethylthiocodide results from heating bromo- or /3-chlorocodide with ethyl mercaptan and aqueous sodium hydroxide at 100° C. [2] it is isomerized to fi-ethylthiocodide on heating with alcoholic sodium ethoxide, a reaction that occurs when bromo- and /3-chlorocodide are heated with ethyl mercaptan and alcoholic sodium ethoxide [1-2]. From the latter reaotion a small quantity of a substanoe named y-othylthiocodido was... 

Benzisothiazolones 385 containing sulphur leaving groups were prepared via thioderivatives 383 [103,124]. The functionahsation of the nitrogen atom with a sulphur containing chain was achieved in two different ways depending on the substituent linked to the sulphur atom. The first one consists in the reaction of sulfides 384 (R = Me, Ph) with the sodium salt of saccharin 363 (R = H) in DMF affording 383. Alternatively, compounds 383 (25-60 overall yields) were prepared from the chloromethyl derivative 365 (R = H) and the appropriate mercaptan in the presence of DBU/MeCN or TEA/THF. Thiophenol reacted with bromo derivative 368 (R = H) in the presence of TEA. Sulfones n = 2) or sulfoxides (n = 1) 385 were prepared with m-chloroperbenzoic acid and their distribution depended on the stoichiometry of the oxidant and on the kind of R and R on 383 (Scheme 92). 

Preparation by reaction of 30% methyl mercaptan with 2-(p-bromo benzoyl)-4-tert-butylphenol in the presence of sodium methoxide in refluxing methanol for 4 days (34%) [817]. 

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