Sulphonyl sulphoxides

Sulphonyl phosphates, reactions of 638 Sulphonyl radicals 215 cyclization of 1099 ESR spectra of 1090-1093 formation of 1094-1098 structure of 1090-1094 thermodynamic data for 1094 Sulphonyl sulphenes 196 Sulphonyl sulphoxides alkylation of 311 synthesis of 262... 

Formation of hydrogen bonds between phenols and naphthols on the one hand, and dimethyl, divinyl, diphenyl sulphoxides and other sulphinyl or sulphonyl derivatives on the other, have also been documented in the literature95-97. 

Intramolecular hydrogen bonds between sulphinyl or sulphonyl groups and hydroxyl groups have also been described106,107. The IR shifts Vjq in these experiments were found at around 1005-1010cm 1108 U0. Several other papers which describe hydrogen bonds of sulphoxides and sulphones are given in References 111-120. 

D. Protonation of the Sulphinyl or Sulphonyl Oxygen Atoms and Basicities of Sulphoxides and Sulphones... 

The use of chlorine as an oxidizing agent for the conversion of sulphoxides into sulphones is completely unsuccessful under anhydrous conditions. In aqueous solutions, the sulphone is formed but this is usually part of a complex mixture of chlorinated sulphoxides, chlorinated sulphones and sulphonyl chlorides89, so that the reaction is usually not very useful as a preparative method for alkyl sulphones. Dimethyl sulphone has however been obtained in 70% yield in one isolated case90. In methanol solution dibenzyl sulphoxide is cleanly oxidized to dibenzyl sulphone and benzyl sulphonyl chloride in reasonable overall yield91. 

A few studies are reported which describe the direct oxidation of sulphoxides to sulphonic acids, sulphonyl halides, thiosulphonates and sulphate. These reactions will be considered in this section but it should be noted that they are rarely of synthetic utility. 

As has been mentioned in an earlier section, aqueous chlorination of sulphoxides leads to sulphones. If excess reagents are used, sulphonyl chlorides may be formed directly from sulphoxides in good yields (equation 75)89,90,193. In order for this reaction to be synthetically useful, the sulphoxide used should be symmetrical. The product is presumably formed in a stepwise manner via the sulphinyl chloride [RS(0)C1] and the sulphinic acid [RS(0)0H]. In the case of chloromethyl dichloromethyl sulphoxide, the only sulphonyl chloride formed is chloromethanesulphonyl chloride (equation 76) and this may be readily separated from the other products by distillation90,193. Similarly, oxidation of dichloromethyl methyl sulphoxide and methyl trichloromethyl sulphoxide with chlorine in aqueous acetic acid leads to the formation of methanesulphonyl chloride in 75% and 86% yields respectively. Other species are also produced but these are much more volatile and thus easily removed (equations 77 and 78). In the absence of acetic acid the yields are somewhat reduced. 

Absorption spectroscopy of sulphonyl radicals 1093, 1094 of sulphoxides 895, 897, 902-905 Acetoxysulphones 953 electrochemical reactions of 1036, 1037 / -Acyloxysulphones, desulphonylation of 948 Alcohols... 

Since sulphones 204 are easily available compounds one would expect that they could be used as starting materials for the preparation of sulphoxides via the selective removal of one oxygen atom from the sulphonyl group (equation 112). Up to now, there is only one example reported of a direct reduction of a sulphone to a sulphoxide. The bicyclic dideuterio sulphone 205 after 24 h treatment with three-fold excess of diisobutyl aluminium hydride in boiling dichloromethane gave the corresponding sulphoxide 206 in 36% yield (equation 113). A two-step procedure for the selective reduction of sulphones to sulphoxides, which involves an initial reaction of sulphone 204 with aryldiazonium tetrafluoroborate 207 to form aryloxysulphoxonium salt 208 and its subsequent reduction (equation 114), was alluded to by Shimagaki and coworkers and... 

Photolysis of sulphonyl azides in dimethyl sulphoxide with 2537 A light gives IV-sulphonylsulphoximines 12 in 15—50% yield 5>. The reaction was formulated as going via a nitrene intermediate which was trapped by the nucleophilic solvent... 

In contrast to the problems encountered on photolysis of alkyl- and aryl-sulphonyl azides, we have found that ferrocenylsulphonyl azide 74 is smoothly decomposed by 3500 A light in cyclohexane or in benzene to give ferrocene 15, ferrocenylsulphonamide 16 and the novel bridged [2]ferrocenophanethiazine 1,1-dioxide 17 24>. The yield of 17 varied with the nature of the solvent, being 13.3% in cyclohexane, 67% in benzene, and zero in dimethyl sulphoxide or DMSO/benzene 25>. 

Dimethyl sulphoxide (amounting to slightly more than equimolar with azide and less than 1% overall concentration in solution in methanol) accelerates the copper-catalyzed decomposition and the only product formed (97%) is the sulphoximine (21). Even in the absence of copper, DMSO and benzenesulphonyl azide were found to undergo a slow reaction in boiling methanol to give 21 (< 40%). It was suggested33) that the sulphonyl azide itself (slow) or the copper complex 24 (fast)... 

Direct sulphanylation of activated methylene groups to form methyl thioethers is possible under basic conditions, when the stabilized carbanion reacts with 5-methyl methanethiosulphonate. The reaction has been applied successfully in, for example, reactions with p-keto sulphoxides [59] and a-sulphonyl acetic esters [60] (Scheme 4.13). 

Sulphoxides, sulphates and sulphonyl compounds have also been used as substrates in stannane-mediated reductions. Gethin and Simpkins reported the Bu3SnH-mediated removal of the tosyl group in substrate (79) in their preparation of protected thymine polyoxin C (equation 53)293. Similarly, Xu and Lu described the removal of the tosyl group in 80 under similar conditions during their synthesis of pentabromopseudilin (equation 54)294. Padwa and his associates utilised B SnH to remove the sulphone moiety in cyclopentenone (81) (equation 55)295, while Wnuk and coworkers discuss... 

Sulphoxides, sulphates and sulphonyl compounds have also been used as substrates in stannane-mediated reductions. Gethin and Simpkins reported the Bu3SnH-mediated removal of the tosyl group in substrate (79) in their preparation of protected thymine... 

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