Sulphenic acid

Preparation.—It is possible to review syntheses of sulphenic acids and to refer now to stable products as well as fleeting species that need to be trapped in order to verify their existence. Further details of the stable penicillin-derived sulphenic acid (72) described in Volume 3 are available. The anion of (72) is, however, 

Elimination reactions leading to simple sulphenic acids have been described earlier in this chapter, in the review of recent literature covering properties of 

While Cope-type elimination from -alkylidenesulphinamides gives a sulphenic acid, this undergoes further condensation reactions in the absence of a trapping agent, but, in the presence of trimethylsilyl chloride, the trimethylsilyl ester (a convenient stable source of the sulphenic acid) is formed.  

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Jones and coworkers200 found that a variety of sulphenic acids may be generated by thermolysis of the readily available /J-cyanosulphoxides (equation 81) and observed their highly regiospecific addition also to non-conjugated alkynes (Table 12). As expected for a pericyclic mechanism, the reaction afforded the product of a stereospecific cis-addition. However, the regioselectivity of the addition suggests that the partial carbon-sulphur bond in the transition state 148 is polarized in such a way that the carbon atom has some cationic character (equation 82). 

For a recent discussion on the stereochemical aspects of the Diels-Alder reaction with vinyl sulphoxides see References 662, 663. It should be pointed out that vinyl sulphoxides can be considered in [2 + 4]-cycloadditions as acetylene synthons since the sulphinyl moiety may be removed from the product by sulphenic acid elimination. Paquette and coworkers took advantage of this fact in the synthesis of properly substituted anthracenes 562664, (equation 360). 

In a set of volumes on sulphur-containing functional groups, the volume on the sulphonium group appeared in 1981 (in two parts). The present volume deals with sulphones and sulphoxides and further volumes, one on derivatives of sulphinic acids and another on derivatives of sulphenic acids, are now in the course of preparation, with a volume on sulphonic acid derivatives planned for the more distant future. 

The Chemistry of Sulphinic Acids, Esters and Derivatives The Chemistry of Sulphenic Acids, Esters and Derivatives... 

Reaction of the carbanion of chloromethyl phenyl sulphoxide 409 with carbonyl compounds yields the corresponding 0-hydroxy adducts 410 in 68-79% yield. Each of these compounds appears to be a single isomer (equation 242). Treatment of adducts 410 with dilute potassium hydroxide in methanol at room temperature gives the epoxy sulphoxides 411 (equation 243). The ease of this intramolecular displacement of chloride ion contrasts with a great difficulty in displacing chloride ion from chloromethyl phenyl sulphoxide by external nucleophiles . When chloromethyl methyl sulphoxide 412 is reacted with unsymmetrical ketones in the presence of potassium tcrt-butoxide in tert-butanol oxiranes are directly formed as a mixture of diastereoisomers (equation 244). a-Sulphinyl epoxides 413 rearrange to a-sulphinyl aldehydes 414 or ketones, which can be transformed by elimination of sulphenic acid into a, 8-unsaturated aldehydes or ketones (equation 245). The lithium salts (410a) of a-chloro-/ -hydroxyalkyl... 

G. Capozzi, G. Modena, and L. Pasquato, in The Chemistry of Sulphenic Acids and Their Derivatives, S. Patai, ed., Wiley, Chichester, 1990, pp. 446-460. 

S. Patai, ed., The Chemistry of Sulphenic Acids and Their Derivatives, Wiley, Chichester, 1990. 

Sulphoxides and selenoxides undergo syn elimination under thermal conditions. A 1,4-elimination of sulphenic acid from an allyl sulphoxide leads to dienes (equation 20)50. Precursor sulphoxides are generated by oxidation of corresponding sulphides. This reaction, however, did not give good results when applied to more complicated systems51. 

The chemistry of sulphinic acids, esters and their derivatives The chemistry of sulphenic acids and their derivatives The chemistry of enols... 

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