Diaryl sulphones

Truce also examined a few examples of the cleavage of sulphones with sodium in liquid ammonia97 and found essentially similar results except that diaryl sulphones were reduced to sulphinate salts instead of to arylthiolates as with the lithium reductions. Dialkyl sulphones were unreactive towards sodium in liquid ammonia. 

Of some relevance in this connection is a study216 on the structure of the anion radicals formed when diaryl sulphones react with n-butyllithium in hexane-HMPA solution under an argon atmosphere. Apparently, a dehydrogenative cyclization and a further one-electron reduction occurs to produce the anion radicals of substituted dibenzothiophene-S, S-dioxides. These anion radicals were studied by ESR spectroscopy. 

Consequently, in conducting aprotic media, most of the diaryl sulphones follow the scheme written below for diphenyl sulphone ... 

The influence of the steric effect in the ortho position is particularly well demonstrated in Table 3, giving, among others, data for two amino diaryl sulphones. 

TABLE 5. Analytical and coulometric data concerning some diaryl sulphones and related compounds in aprotic conditions... 

Dialkyl sulphones are not reducible at a mercury cathode. Aryl alkyl and diaryl sulphones are however reduced with cleavage of a carbon-sulphur bond. Polaro-graphic half-wave potentials for this process are given in Table 5.6. One-electron addition in aprotic media to phenyl methyl sulphone [66] and to diphenyl sulphone [67] leads in both cases to a delocalised radical-anion in which the sulphone grorqj can be described as contributing a vacant symmetrical dx-orbital to the conjugated system. Phenyl methyl sulphone radical-anion is prepared and characterised in liq-... 

Preparations from sulphinic acids, SO2, other simple sulphur compounds, and sulphonyl halides are reported in the papers that are listed (with brief details) at the end of this section. The AlClj-catalysed rearrangement of an aryl arenesulphonate gives the corresponding diaryl sulphone. ... 

The polarographic reduction potentials of the sulphonic acids and derivatives (25 X = heteroatomic groups) and the carbocyclic (25 X = Ph) and heterocyclic sulphones could be well rationalized by HMO calculations. Mesomeric interaction between the conjugated v systems and the SOagroup in diaryl sulphones does not affect the S==0 bonds the case of cyclic sulphones derived from thiophens is different, a finding recently established by i.r. data. ... 

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