Diarylsulfides

As expected, the addition of arenediazonium ions to thiophenols does not involve the thiophenol molecule, but rather the thiophenoxide ion (Price and Tsunawaki, 1963). Dediazoniation with the formation of a diarylsulfide (6.16) is competitive with the formation of the diazo thioether 6.15 (Scheme 6-9 van Zwet et al., 1970). Whereas the early investigators detected only one isomer, (Z)- and (ii)-forms were... 

Both cis- and rrans-l-arylsulfonyl-2-arylsulfenyl propenes (56) underwent a Smiles rearrangement under electron impact at 20 and 70 eV and formed a diarylsulfide ion [M — 104]+ (equation 27a)39 through a process where a bond between the R C H group and the sulfide sulfur is formed and a rearomatization occurs by a loss of the neutral thiirene dioxide or a simultaneous expulsion of SOz and propyne. The ion m/z 148 was also obtained from all of the sulfonyl-sulfides, 56 (equation 27b) and here the loss of R2 seemed to be related to the bond strength39. In addition to the above compounds 56 exhibited some simple cleavages before and after sulfone-sulfinate rearrangements. 

On the contrary, arylalkylsulfides ArSR and diarylsulfides ArSAr, in general, can exhibit [206] an irreversible two-electron cathodic step at fairly negative potentials. 

More variation is available when the hetero-ring is closed using the suliinic acid functionality in a diarylsulfide carrying the suliinic acid at an ortho position (Scheme 11) (IV,C). 

The thiol-diarylsulfide 101 produced a Meisenheimer salt that underwent rearrangement and eventually resulted in the production of 1,3-dinitrothianthrene (75ZOR1440). 

A comparable positive influence as experienced with anodic dimerization of olefins, styrene in particular, exerts carbon anodes on the anodic formation of trisarene sulfonium cations by anodic coupling of diarylsulfide radical cations to arenes (226-228). 

Dilithiation of the diarylsulfide 528 and reaction with methyl chloroformate affords the 1,8-disubstituted thiox-anthone in ca. 40% overall yield from 3-methoxythiophenol (Scheme 210) <2005OL2739>. 

Sulfur can be introduced into a diazonium salt by the SN1 reaction shown in Figure 5.51. In order to prevent the reagent from effecting a double (rather than a mono-) arylation at the sulfur atom, potassium xanthogenate instead of sodium sulfide is used as the sulfur nucleophile. The resulting S-aryl xanthogenate C is hydrolyzed. In this way diarylsulfide-free aryl thiol B is obtained. 

Diarylsulfides are lithiated ortho to sulfur, but less efficiently than diaryl ethers dibenzothiophene 234 for example lithiates to give 235 and hence 236. Highlighting preferential lithiation at the more acidic positions ortho to O, 237 gives 238 rather than 239.107... 

Benzothiepines 69 have been synthesised by a gold-catalysed rearrangement of homopropargyl arylsulfoxides 68 <07JACS4160>. The dibenzothiepine 71 was synthesised by intramolecular Friedel-Crafts acylation of a diarylsulfide 70 which was formed by the copper mediated substitution of an appropriately substituted aryl derivative with thiophenol... 

The role of a peptizer is to enhance the mechanochemical degradation of a polymer, such as the mastication of natural mbber, and known peptizers are thiols and diarylsulfides. The mechanism of action is believed to be the redox decomposition of hydroperoxides (Scott, 1993b), as shown in Scheme 1.70(a) ... 

Depending on the nature of the counterion, triarylsulfonium salts are more or less stable. The most stable compounds have a non-nucleophilic counterion. On the other hand, the presence of a nucleophilic counterion such as a halide (Cl, Br or I) frequently results in the relatively facile decomposition by thermolysis to afford quantitatively the diarylsulfide and the corresponding aryl halide. The observation of the preferential relief of the steric strain in the case of phenyl-p-tolyl-(2,5-dimethylphenyl)sulfonium salts (23) was explained by the intramolecular decomposition of a first formed tetracoordinate intermediate. 35.36... 

The reaction of triarylsulfonium halides with sodium alkoxides at high temperatures afforded mixtures of alkyl aryl ethers (24), diarylsulfides, hydrocarbons and aldol resins or a ketone if the alkoxide is derived from a secondary alcohol.25,36,38-41... 

Triarylsulfonium halides reacted with sodium arylthiolates to afford mixtures of diarylsulfides. The reaction can be explained by a ligand coupling process taking place on a (arylthio)triarylsulfurane and is free of any competing free radical chain component as no diaryldisulfides were observed.25.39... 

The reaction of triarylsulfonium halides with piperidine, used as solvent, in the presence of potassium amide at 100-110°C afforded a mixture of the derived AT-arylpiperidine (25) in high yield, together with the diarylsulfide and/or arylthiol derived from the reagent by ligand exchange.39... 

Ellwood [33] described the synthesis of triarylsulfonium salts via reaction of a diarylsulfide, Lewis acid catalyst, and a halogen in the presence of an inert solvent. Anion exchange afforded the desired salt. 

Dektar and Hacker have studied the sensitized photolysis of sulfonium salts extensively [70,83]. Like diphenyliodonium cation, triphenylsulfonium is reduced by anthracene singlet to triphenylsulfur radical which cleaves incage to yield phenyl radical and diphenylsulfide [91]. Naphthalene sensitized photolysis of triarylsulfonium salts yielded some of the same photoproducts observed in direct photolysis, namely arylated diarylsulfides [94a] ... 

This result contrasts with the observations on anthracene sensitized photolysis, wherein no arylated diarylsulfides are observed. Naphthalene cation radical is sufficiently oxidizing (naphthalene Eox = 1.54 V versus SCE) to oxidize diphenylsulfide ( ox = 1.31 V versus SCE), whereas anthracene cation radical cannot (anthracene Eox = 1.09 V versus SCE) [94], Thus, diphenylsulfide cation radical/phenyl radical pair is formed by two sequential single electron transfer reactions in-cage, the subsequent chemistry being the same... 

Alkyl sulfides turned out to be good inhibitors because they react readily with peroxides to form sulfoxides and sulfones, whereas thiophenes and diarylsulfides, which form sulfoxides and sulfones more slowly (the sulfur electron pair is more involved in resonance stabilization), were not such good inhibitors. Experiments with the sulfides themselves showed them to react slowly with oxygen, therefore they were not acting in a sacrificial manner. 

The most troublesome consequence of using concentrated sulfuric acid is in its sulfonating property. An aromatic molecule is likely to be more easily oxidized to a cation radical if it contains electron-donor substituents. But these substituents also make the molecule more susceptible to electrophilic attack, i.e. to sulfonation. This is the case, for example, with aromatic ethers and diarylsulfides. For example, 1,4-dimethoxybenzene undergoes 70-90% sulfonation within a few minutes in concentrated sulfuric acid, and only a low concentration of the cation radical can be obtained (Nishinaga et al.,... 

Treatment of triarylsulfonium salts with vinyllithium leads to quantitative 5delds of styrene and diarylsulfide. Again, use of tri- -tolylsulfonium fluoroborate produces only -methylstyrene, ruling out benzyne routes. 

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