Disulfides, hydroxy sulfenylation

Sulfonic acids are conveniently made by oxidation of the corresponding thiones or disulfides. Direct sulfonation is best effected with chlorosulfonic acid. Direct thiation can be achieved with sulfenyl chlotides to give 5-thiopyrimi-dines in excellent yields. For example, the reaction of 6-hydroxy-4(l//)-pytimidinone [4,6(1//,5//)-pyrimidinedione] 72 with benzylsulfenyl chloride or 2-methoxyphenylsulfenyl chloride gave the respective 5-thio derivatives 73 in 96% and 97% yields <1993SC2363, 2001JME3355>. 

In 1979 it was reported20 that by converting the 2-a-hydroxy group of 2-a-hydro-xyethyl-3,4-dimethylthiazolium salts to an ether, the enamine could be generated, as deduced from its product with the oxidizing agent diphenyl disulfide, generating a tetrahedral intermediate at the C2a position by sulfenylation (equation 2). This would be consistent with nucleophilic and/or redox reactivity of the enamine at the C2a position. 

Alkyl and aryl pyridyl disulfide-W oxides are also effective sulfenylating agents. Thus, treatment under prolonged reaction time of 2,2 -dipyridyl disulfide-)V,) -dioxide with 2 equiv of thiol generates s)mimetrical disulfides and 7V hydroxy-2-thiopyridone as shown in eq 3. ... 

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