Sulfonyloxy group reaction with nucleophiles

Sulfonyloxy groups may undergo bimolecular replacement reactions with nucleophiles, either external or internal, according to their axial or equatorial disposition and/or potential neighboring-group participation. 

In a preliminary step, adjacent ester groups undergo initial hydrolysis or alcoholysis, by the base, to the oxide anion. This step is reasonable for carboxylic esters, which are rapidly hydrolyzed under the conditions usually employed, but is rather more surprising for sulfonic esters, which are usually hydrolyzed only slowly by the nucleophilic attack on sulfur required for this reaction. With these disulfonic esters, the ease of hydrolysis has been explained by the inductive effect of the adjacent sulfonyloxy group.7... 

Thio-D-xylopyranose has been the sugar of this type most thoroughly investigated. Its synthesis was reported in 1961, independently and simultaneously from three different laboratories. With sodium thiocyanate, l,2-0-isopropylidene-5-0-p-tolylsulfonyl-a-D-xylofuranose (211) gives a thiocyanate that reacts with sodium sulfide to give l,2-0-isopropylidene-5-thio-a-D-xylofuranose (212). A better synthesis is the treatment of 211 with sodium thiosulfate, followed by reduction of the resultant Bunte salt with sodium boro-hydride. The same compound 212 is obtained by nucleophilic replacement of the 5-sulfonyloxy group in 211 by treatment with potassium thioacetate followed by deacetylation to 212, or by the reaction of 211 with sodium a-toluenethioxide, followed by scission of the resultant S-benzyl compound with sodium in liquid ammonia. 

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