The Renaissance of Alkali Metabisulfites as SO2 Surrogates

Abstract The upsurge of interest in the development of methodologies for the construction of sulfur-containing compounds via the use of expedient reagents has established sustainable tools in organic chemistry. This review focuses on sulfonylation reactions using inorganic sulfites (Na 2 S 2 O 5 or K 2 S 2 O 5 ) as the sulfur dioxide surrogates. Compared to the bis-adduct with DABCO, which is an excellent surrogate of gaseous SO 2 , the use of sodium or potassium metabisulfites as SO 2 surrogates are equally efficient. The objective of the current review is to exemplify recent sulfonylation reactions using inorganic sulfites. For better understanding, the review is categorized according to the mode of reactions: transition-metal-catalyzed SO 2 insertion, metal-free SO 2 insertion, and visible-light-mediated SO 2 insertion. All the reactions in each of the sections are illustrated with selected examples with a pertinent explanation of the proposed mechanism. 1 Introduction 2 Outlines of the Reactions Involving SO 2 Insertion 2.1 Transition-Metal-Catalyzed SO 2 Insertion 2.2 Transition-Metal-Free SO 2 Insertion 2.3 Visible-Light-Mediated SO 2 Insertion 3 Conclusion and Outlook