5- Arylation diarylsulfide

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... 

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. 

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... 

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... 

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