Radicals and Sulfur Dioxide: A Versatile Combination for the Construction of Sulfonyl‐Containing Molecules

Abstract

Molecules containing a sulfonyl functionality, such as sulfones, sulfonyl chlorides or sulfonamides play an important role in organic chemistry and have found widespread application, especially in the construction of biologically active compounds. Recently, methods for the synthesis of the sulfonyl moiety utilizing sulfur dioxide as a key building block have received considerable attention. In this context, radical-based transformations with sulfur dioxide have emerged as a new and attractive approach for the construction of the sulfonyl functional group. This short review highlights recent advances in the use of sulfur dioxide in radical reactions and covers the historical background, which forms the basis for these current progresses. Limitations of the existing methods and potential further developments will be discussed.

Metal Free Sulfonylative Spirocyclization of Alkenyl and Alkynyl Amides via Insertion of Sulfur Dioxide

“…[12a] Subsequently, Wu pioneered the use of DABSO for the generation of aryl sulfonyl radicals which were shown to partake in a variety of elegant transformations. [13,14] However, spirocyclization with DABSO derived sulfonyl radicals remains elusive. Furthermore, only a handful of reports exist for the synthesis of functionalized azaspiro [4,5]-decanes.…”

Three‐Component C–H Bond Sulfonylation of Imidazoheterocycles by Visible‐Light Organophotoredox Catalysis

“…[ 6 ] More recently, a multicomponent reaction involving two pre‐activated sulfur‐free partners and SO 2 has emerged as an appealing route for the direct introduction of the sulfone moiety. [ 7,8 ] The importance of this approach relies on the development of bench‐stable and easy handled SO 2 surrogates which circumvent the toxicity and the drawbacks associated with handling gaseous sulfur dioxide. [ 9 ] In the omnipresent field of C–H bond functionalization, sulfonylation has also become a subject of significant work with achievements made using one sulfur partner often sulfonates or sulfonyl halides.…”

Direct Metal‐ and Reagent‐Free Sulfonylation of Phenols with Sodium Sulfinates by Electrosynthesis

“…Aryl sulfones are used in many different areas, especially in pharmaceutical sciences . In active pharmaceutical ingredients the sulfone group represents an important structural motif . Significant representatives among them are the antibiotic dapsone ( 1 ), which is used for the treatment of leprosy and malaria.…”