Imidazolium and Benzimidazolium Sulfonyl Salts: Versatile Functional Group Transfer Reagents

Imidazolium and benzimidazolium salts have been known for decades as ionic liquids and precursors to N-heterocyclic carbenes (NHCs). Lately, N-sulfonyl functionalized imidazolium and benzimidazolium salts have gained popularity as functional group transfer reagents. This review focusses on the facile use and transition of imidazolium and benzimidazolium sulfonyl salts from electrophilic hubs to photocatalytic reagents in order to efficiently transfer valuable functional groups onto organic molecules. These salts have been classified according to the functional groups they transfer e.g., arylsulfonyl, diazo, sulfonylazide, fluorosulfonyl, fluoroalkyl and thioaryl. Furthermore, this review highlights the usefulness of these reagents in biomedical and materials science.