Aryl phenyl sulphones

Sulphone cleavage is involved in a number of otherwise unrelated observations 2-(hydroxyamino)aryl phenyl sulphones or bis-(2-hydroxy-amino)aryl sulphones disproportionate into arylsulphinate and 2-hydroxy-2 -(arylsulphonyl)azoxybenzene (135) in aq. NaOH at 20 while... 

Electrochemical reduction of aryl sulphones in methanol leads to cleavage of one carbon-sulphur bond in a two-electron process. Alkyl aryl sulphones with an electron donating substituent in the aryl ring give the arenesulphinic acid and an alkane [68, 69]. Methyl phenyl sulphone and alkyl aryl sulphones with an electron withdrawing substituent in the aryl ring are cleaved to the substituted arene and the alkylsulphinic acid [70], see Scheme 5.2. In addition, a bulky orfAo-substituent such as tert.-butyl favours cleavage to the arene and alkanesulphinic acid [71]. 

Retinol Derivatives. Aryl sulphones have been used in two new syntheses in the vitamin A series. Reaction of /8-cyclocitryl phenyl sulphone (102) with the bromo-compound (103) gives the intermediate sulphone (104), which on base-catalysed elimination affords methyl retinoate (98). Alternatively retinol (99) has been prepared in high yield by condensation of the C15 bromide (105) with the C5 hydroxy-sulphone (106), followed by elimination of sulphinic acid. The syntheses... 

Ring Substitution of Aryl Sulphones.—The influence of the sulphonyl group on reactions of substituted phenyl sulphones has been studied in relation to nucleophilic substitution of p-h dogenophenyl aryr or trifluoromethyl aryl sulphones/ by phenoxide anions and other species. 

Peroxybenzoic acid readily oxidizes aryl and alkyl sulphoxides in acetone, methylene chloride or chloroform solutions, to the sulphone in high yield . The reaction is second order and acid catalysed as is the reaction with peracetic acid . The rate of oxidation is about five times faster than when peracetic acid is used. Other work considering the oxidation of sulphoxides with peracids gathered kinetic evidence and showed that the reaction was indeed second order and that the reaction involved nucleophilic attack by the sulphoxide sulphur atom on the peracid moiety. A further study by the same authors showed that with benzyl and phenyl alkyl sulphoxides the rate of reaction was very sensitive to the inductive effect of the alkyl group. Support for the nucleophilic attack by the sulphur atom on the peracid in acidic solution was forthcoming from other sources . ... 

The anodic oxidation reaction of sulphoxides was not much studied, and just a few reports are available so far. The conversion into the corresponding sulphones of some phenyl alkyl and diaryl sulphoxides (oxidation potential for 86 + 2.07 V vs. SCE in acetonitrile/NaC104 electrolyte, Pt anode) has been reported. Similarly, diphenyl suiphoxide was long known to be transformed in a quantitative yield into the sulphone (Pt anode, solvent glacial acetic acid). Additional examples of the oxidation of a suiphoxide function attached to aryl groups are available . 

Aryl glycosides of 2-amino-2-deoxy sugars, as might be expected, can be prepared by similar techniques as was illustrated by the synthesis of phenyl 3,4,6-tri-0-acetyl-2-acetamido-2-deoxy-p-D-glucoside and -D-galactoside by toluene -sulphonic acid catalysed reactions between phenol and the hexosamine penta-acetates These products were then anomerised using zinc chloride as catalyst to provide means of obtaining -anomers. 

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-... 

A number of functional group can be converted to phenols, e.g. Sulphonic acids and amino groups which have already been mentioned. Phenyl esters can be hydrolysed (Following fig.). Aryl ethers can be cleaved. The bond between the alkyl group and oxygen is specifically cleaved because the Ar-OH bond is too strong to be cleaved. 

Forbes and co-workers9 have extensively studied the ultra-violet absorption spectra of several series of disubstituted benzene derivatives acetophenones, benzoic adds, benzaldehydes, phenylbenzoates, acetanilides- nitrobenzenes, anilines, fluorobenzenes, chlorobenzenes, phenols and anisoles. They have collected valuable data and interpreted them in terms of the resonance and steric interactions of substituents. Baliab. and co-workers27 have studied the absorption spectra of aryl sulphones and sulphoxides. The absorption spectra of substituted phenylazides28 and phenyl isothiocyanates29 have been discussed by Rao et al. 

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