2-fluoro-5-(2-methyl-[1,3]dioxolan-2-yl)-benzenesulfonamide → 5-(2-Bromomethyl-[1,3]dioxolan-2-yl)-2-fluoro-benzenesulfonamide

A solution of 8.4 g (0.0225 mole) of phenyltrimethylammonium tribromide in 20 mL of CH3CN was added dropwise to a solution of 5.2 g (0.022 mole) 2-fluoro-5(2-methyl-[1,3]dioxolan-2-yl)-benzenesulfonamide III in 100 mL of CH3CN. The reaction was stirred at room temperature for 1 hr. The solvent was evaporated in vacuo. The residue was dissolved in EtOAc, washed with water, dried over Na2SO4 and evaporated. The residue was purified by column chromatography on silica gel eluting with CH2Cl2/Et2O::9/1 to give 4.6 g of IV (62%) as an oil. CH2Cl2/Et2O::9/1 single-spot material Rƒ 0.30.1H NMR (300 MHz CDCl3) δ: (3.68, s, 2H), (3.80,m , 2H), (4.21, m, 2H), 5.15, broad s, 2H), (7.26, t, 1H), (7.75, m, 1H), 8.15, dd, 1H).