Sulfonic from thiols

Tributyltin hydride, 316 Zinc iodide, 280 From alkyl halides Lithium aluminum hydride-Ceri-um(III) chloride, 159 Palladium catalysts, 230 Sodium cyanoborohydride-Tin(II) chloride, 280 From alkyl sulfonates Lithium triethylborohydride, 153 From thiols... 

SECTION 138 Halides and Sulfonates from Alcohols and Thiols... 

Cysteic acid is obtained in nearly quantitative yield from cysteine with aqueous hydrogen peroxide in the presence of iron(II) ions.397 Molybdates and tungstates have also been used as effective catalysts for similar transformations.398 An excellent route for the oxidation of 2-thioethanol to isothionic acid has been developed.399 Heteropolyoxometallates supported on alumina400 can also be used to oxidize a range of organo-sulfur compounds. For example, alkyl monosulfides to sulfoxides and sulfones, and thiols to sulfonic acids are a few possibilities (Figure 3.98). 

SECTION 138 HALIDES AND SULFONATES FROM ALCOHOLS AND THIOLS... 

General Reaction Chemistry of Sulfonic Acids. Sulfonic acids may be used to produce sulfonic acid esters, which are derived from epoxides, olefins, alkynes, aHenes, and ketenes, as shown in Figure 1 (10). Sulfonic acids may be converted to sulfonamides via reaction with an amine in the presence of phosphoms oxychloride [10025-87-3] POCl (H)- Because sulfonic acids are generally not converted directiy to sulfonamides, the reaction most likely involves a sulfonyl chloride intermediate. Phosphoms pentachlotide [10026-13-8] and phosphoms pentabromide [7789-69-7] can be used to convert sulfonic acids to the corresponding sulfonyl haUdes (12,13). The conversion may also be accompHshed by continuous electrolysis of thiols or disulfides in the presence of aqueous HCl [7647-01-0] (14) or by direct sulfonation with chlorosulfuric acid. Sulfonyl fluorides are typically prepared by direct sulfonation with fluorosulfutic acid [7789-21-17, or by reaction of the sulfonic acid or sulfonate with fluorosulfutic acid. Halogenation of sulfonic acids, which avoids production of a sulfonyl haUde, can be achieved under oxidative halogenation conditions (15). 

Photooxidafions are also iudustriaHy significant. A widely used treatment for removal of thiols from petroleum distillates is air iu the presence of sulfonated phthalocyanines (cobalt or vanadium complexes). Studies of this photoreaction (53) with the analogous ziuc phthalocyanine show a facile photooxidation of thiols, and the rate is enhanced further by cationic surfactants. For the perfume iudustry, rose oxide is produced iu low toimage quantifies by singlet oxygen oxidation of citroneUol (54). Rose bengal is the photosensitizer. 

Zhang and coworkers have reported on a palladium-catalyzed carbon-sulfur cross-coupling of aryl perfluoroalkoxysulfonates with thiols (Scheme 7.78) [91]. The fluorous substrates were obtained from commercially available phenols by treatment with perfluorooctanesulfonyl fluoride (C8F17S02F) under basic conditions. Various thiols were reacted with a slight excess of the perfluorinated sulfonates in a... 

Apart from complex formation involving metal ions (as discussed in Chapter 4), crown ethers have been shown to associate with a variety of both charged and uncharged guest molecules. Typical guests include ammonium salts, the guanidinium ion, diazonium salts, water, alcohols, amines, molecular halogens, substituted hydrazines, p-toluene sulfonic acid, phenols, thiols and nitriles. 

Figure 4.8. The sulfur cycle where S° is elemental sulfur, H2S is hydrogen sulfide, S2032" is thiosulfate, SO32" is sulfite, SO/- is sulfate, R-OSO3H represents a sulfate ester, R-SO3H a sulfonic acid, R-S-R a thioether, and R-SH a thiol. (Adapted from Coyne MS. Soil Microbiology An Experimental Approach. Boston Delmar Publishers 1999.)...

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