For example, the aliphatic sultone 2 can be named as 3-hydroxy-1-propanesulfonic acid sultone, propane-1, 3-sultone, or more simply as propane γ-sultone. Sultones are important heterocyclic compounds that can introduce alkyl chains carrying the sulfonic acid functionalities and can therefore be used as sulfoalkylating agents. Some review articles have also been published on sultone chemistry in earlier literature, 4− 8 but there is no literature survey covering the recent developments in sultone synthesis. This review compiles the recent developments (focusing on the period 2000− 2011) in the synthesis of sultones.

2. SYNTHESIS OF SULTONES Because sultones are synthetically very useful heterocycles in organic synthesis, many groups are currently working on sultone chemistry. 9− 26 Most of the earlier procedures for sultone synthesis involved either carbanion-mediated sulfonate intermolecular or intramolecular coupling reactions (CSIC reactions) 27 or sulfonation of olefins with dioxane− sulfur trioxide. Recently, many powerful methodologies have been developed for the synthesis of the sultones, such as intramolecular Diels− Alder reactions, ring-closing metathesis, Pdcatalyzed intramolecular coupling reactions, Rh-catalyzed C− H insertion, Rh-catalyzed carbene cyclization cycloaddition cascade reactions, etc. For clear presentation, the syntheses of sultones have been divided into two categories:(i) asymmetric synthesis and (ii) nonasymmetric synthesis, which were then subdivided according to their reaction types. 2.1. Asymmetric Synthesis of Sultones Asymmetric syntheses of sultones became an attractive goal for the researchers because chiral sultones can offer novel possibilities for stereoselective transformations. There have been several new developments in the asymmetric synthesis of sultones in the recent literature, which are discussed in the following sections.