Alkyl S-[3]betylates (S,S-dialkyl-S-3[(alkyloxy)sulfonyl]propylsulfonium salts), the first examples of S-betylates (sulfonioalkanesulfonic esters), have been synthesized by two routes, and their suitability as intermediates in the transformation of alcohols by nucleophilic substitution reactions examined. They have been found to react readily in stoichiometric phase transfer processes, including substrate–reagent ion-pair reactions, like their previously studied nitrogen analogues, with the following particular features: (a) they may be used with basic nucleophiles (unlike [2]betylates), (b) they are more simply made from commercially available starting materials than [3]betylates, and (c) they can be made by a route that avoids a final alkylation step.