Palladium-Catalyzed Borylation of Aryl Sulfoniums with Diborons

Palladium-catalyzed borylation of aryl sulfonium salts with bis(pinacolato)diboron has been achieved. Because of the sufficient reactivity of aryl sulfoniums and less catalyst-poisonous property of the leaving dialkyl sulfides, the present borylation proceeded under mild reaction conditions. Various functional groups, such as formyl, acetyl, cyano, nitro, and hydroxy groups, were well-tolerated. Aryl sulfoniums were easily prepared from the corresponding aryl sulfides and methyl triflate, and aryl sulfides could be transformed to the corresponding arylboronate esters in one-pot manners. The methylation selectively activated poorer leaving alkylsulfanyl units to culminate in selective borylation over chloro, tosyloxy, and better leaving arylsulfanyl and trifluoromethylsulfanyl units.