DABSO as a SO₂ Source Usable for Direct Sulfonylative-Suzuki Coupling of Aryl Boronic Acids

Bis(sulfur dioxide)-1,4-diazabicyclo[2.2.2]octane adduct (DABSO) has been widely used as a SO₂ source since it was first applied to synthesis of sulfonyl compounds by Willis et al. in 2011.¹⁾ For example, Willis et al. have performed the (CH₃CN)₄CuBF₄ complex catalyzed direct sulfonylative-Suzuki coupling of aryl boronic acids with electrophiles using DABSO as a SO₂ source. In this reaction, nucleophilic aryl sulfinates are formed as a synthetic intermediate, and further react with various electrophiles like epoxides, in situ prepared chloroamines and an active fluorinating reagent (NFSI) to afford the related sulfones, sulfonamides and sulfonylfluorides.²⁾ DABSO can be used as a SO₂ surrogate reagent because gaseous SO₂ is highly toxic, so it is expected to be further applied to organic syntheses.