Diaryl chalcogenides

Table 8 Oxidation and peak potentials of diaryl chalcogenides...

Unlike the aryl methyl selenides, the alkyl aryl selenides with alkyl groups of two carbons or more are able to undergo scission of the radical cation at the Cgp-Se bond, yielding the ArSe radical (Fig. 35). This can impact product distribution, particularly under conditions in which water is not present to react with the radical cation. Trends in ease of oxidation typically seen in series of chalcogen compounds can still be observed, and are consistent with trends in the diaryl chalcogenides and aryl methyl chalcogenides. 

Carbon monoxide diverts the coupling of diaryliodonium salts and arylboronic acids to the generation of diaryl ketones. Additive carbonylation leading to P-substituted butenolides is observed when propargylic alcohols and diaryl chalcogenides are subjected to the carbonylation conditions. 

A particularly valuable route to phenoxathiin utilizes the long-known reactions of diphenyl ether with sulfur in the presence of aluminum chloride. Thianthrene was similarly prepared from sulfur and benzene. These harsh conditions would not be suitable for the preparation of electron-rich alkoxylated dibenzo compounds (181). For the construction of compounds (181), a strategy involving electrophilic ring closure of preformed alkoxylated diaryl chalcogenides (180) was used. Thus, treatment of compounds (180) with sulfur dichloride in dry chloroform provided the derived phenoxathiins (181) in satisfactory yields <88JCS(Pl)2095>. 

Reproduced with permission from Mukherjee N, Chatterjee T, Ranu BC. Reaction under ballmilling solvent-, ligand-, and metal-free synthesis of unsymmetrical diaryl chalcogenides. J Org Chem 2013 78 11110-4, Copyright 2013, American Chemical Society. 

Sequential synthesis of the and anions by electrochemical reduction of the elements Se or Te provides a route to both dialky 1-di- and monoselenides and tellurides [35]. Ultrasound has also been used to promote the electrochemical synthesis of unsymmetrical diaryl chalcogenides typified by 4-phenylseleno- and -tellurobenzonitrile [228]. However, the rate enhancements observed when electrochemical reactions are exposed to ultrasound would appear to stem from the increase in mass transport rather than cavitational effects [229]. 

The diaryl telluride, alkyl aryl telluride, and dialkyl telluride carrying sulfopropyl groups were prepared and were found to be the most efficient tellurium based inhibitors of thioredoxin reductase ever tested. The results clearly showed that of the four cyclic aryl alkyl chalcogenides 162-165, all primitive analogues of vitamin E, only the tellurium compound, 165, showed interesting inhibition characteristics. 

Reaction of aryl diazonium tetrafluoroborate 90 and diaryl dichalcogenides (disul-fane, diselenide, and ditelluride) 91 under ball milling at ambient temperature was applied in the synthesis of unsymmetrical aryl chalcogenides 92 by Ranu et al. 

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