Sulfones from sulfoxides

Many other peroxy acids, such as trifluoroperacetic acid (equation 26), peroxydodecanoic acid (equation 27) and various perbenzoic acids " are also useful oxidants to give a high yield of sulfones from sulfoxides or directly from sulfides under suitable conditions. 

Solutions of KO2 and l8-crown-6 in DMSO cause oxidation of the solvent to die sulfone. The phosphorus-containing peroxy anion (EtO)2P03" obtained on reaction of KO2 widi diefiiyl chlorophosphate [(EtO)2POCl] in acetonitrile has been used to prepare sulfones from sulfoxides at 20 C. Similarly, various sulfoxides are readily oxidized chemoselectively to the sulfones in high yields by 2-nitrobenzene peroxysulfur intermediate (26) generated in situ from 2-nitrobenzenesulfonyl chloride and KO2 (Scheme 8 Ar = 2-N02C6H4). ... 

A number of other oxidants which produce sulfones from sulfoxides are known, such as N02BF4, ° oxygen with Ir or Rh catalysts, ozone,KHSOs (Oxone) and K2S20s. Oxone is a highly chemoselective oxidant for the conversion of sulfides to sulfones without affecting hydroxy or al-kenic groups (equation 37). Similarly flavin (14) oxidizes aryl methyl sulfoxides to sulfones fairly selectively. ... 

Osmium tetroxide is another chemoselective oxidant reported to yield sulfones from sulfoxides. Thus, treatment of a mixture of diphenyl sulfide and sulfoxide with OSO4 in boiling ether ftH 48 h affords di-... 

Peracetic acid (s. a. H202/CHfiOOH) Partial formation of sulfoxides from thioethers Sulfones from sulfoxides s. 13, 152 CHSC002H... 

Sulfones and sulfoxides (145) are obtained usually from the corresponding sulfide by oxidation (Scheme 75) (341). though some of them were prepared from a halothiazole and metal sulfinate (342). 2-Amino-5-acetamidophenylsulfonylthiazole has been prepared by direct heterocycli-zation (343. 344). 

S-Methyl-L-methionine chloride (Vitamin U) [1115-84-0] M 199.5, [a]p +33 (0.2M pK[ 1.9, pKj 7.9. Likely impurities are methionine, methionine sulfoxide and methionine sulfone. from water by adding a large excess of EtOH. Stored in a cool, dry place, protected from light. 

Our discussion concentrates on experimental information providing some insight into the difficulties and limitations of these studies. In places, results from quantum chemical calculations will be invoked for comparison however, a critical analysis of the application of these methods to sulfones and sulfoxides is beyond the scope of this section. As in previous reviews in this series3,6,7, we shall be concerned primarily with the geometrical aspects of molecular structures. 

Several theoretical and experimental characteristics of the sulfone and sulfoxide groups are substantially modified when these are incorporated within a cyclic array. As a rule, the smaller the ring size the larger the deviation from the normal expected properties and behavior of the sulfone and sulfoxide groups. 

The situation is entirely different in the three-membered ring sulfones and sulfoxides the facile thermolytic elimination of S02 from the former is probably their most distinctive (and dominant) chemical reaction, whereas the loss of SO from the latter characterizes both the thiirane and thiirene series2. 

This review is concerned with the formation of cation radicals and anion radicals from sulfoxides and sulfones. First the clear-cut evidence for this formation is summarized (ESR spectroscopy, pulse radiolysis in particular) followed by a discussion of the mechanisms of reactions with chemical oxidants and reductants in which such intermediates are proposed. In this section, the reactions of a-sulfonyl and oc-sulfinyl carbanions in which the electron transfer process has been proposed are also dealt with. The last section describes photochemical reactions involving anion and cation radicals of sulfoxides and sulfones. The electrochemistry of this class of compounds is covered in the chapter written by Simonet1 and is not discussed here some electrochemical data will however be used during the discussion of mechanisms (some reduction potential values are given in Table 1). 

Cation and anion radicals form from sulfoxides or sulfones by either chemical or electrochemical oxidation and reduction, respectively. The ability of compounds to accept... 

TABLE 6. ESR parameters for radical cations arising from sulfoxides or sulfones... 

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