Sulfonic acids reductive desulfurization

Methyl-2-mercaptobenzimidazole 923 is oxidized with ozone to afford mainly sulfonic acid 924 at low temperature (Table 12, entry 1). The formation of desulfurized product 924 is most likely a result of partial oxidation, followed by intermolecular reduction by 923. At higher temperatures and in the presence of nucleophiles, substitution of the sulfonic acid group takes place <1996SC3241>. 2-Mercaptoimidazoline reacts similarly under these conditions. 

Cyclopropyl sulfones 3 are easily reduced to cyclopropanes 4 by treatment with sodium amalgam in refluxing ethanol. Yields above 80% have been reported.However, quite different reaction conditions are required to perform reductive desulfurization of cyclopropanesulfinic acids 5, i.e. the use of mercury(II) chloride, concentrated hydrochloric acid, and heat ethylmagnesium bromide followed by acid has also been used but yields were poor. ... 

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