Potassium acetate (2.5 g, 24.4 mmol) was added to a solution of 4-bromobenzenesulfonamide (2.00 g, 9.32 mmol) and bis(pinacolato)diboron (2.40 g, 9.32 mmol) in DMSO (20 mL) and the mixture was degassed for 45 minutes. Then [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (220 mg, 0.26 mmol) was added and the mixture was heated to 90C for 16 hours. Once cooled, the reaction mixture was diluted with EtOAc (30 mL), washed with water (3 x 30 mL), dried over MgSO4 and concentrated under vacuum. The residue was ground from Et2O (50 mL) and HCl (1 M, 50 mL), and the solid formed was dissolved in CH2Cl2 (30 mL) and filtered through a silica gel pad washed with Et2O, followed by concentration to give phenylsulfonamide-4-boronic acid as an off-white solid, 13% yield, 550 mg.
