To a 250 mL three neck flask fitted with a thermometer, condenser, stirbar, under argon was added the bis-methanesulfonyl derivative 6 (44 g, 0.091 mol) dissolved in DMF (200 mL). Lithium chloride (5.8 g, 0.136 mol) was added in one portion. The reaction mixture was heated to 80° C. with an oil bath. After 90 min the reaction was allowed to cool to room temperature and diluted with 50% ethyl acetate in hexanes (880 mL). The layers were separated and the organic layer was washed with water (2×550 mL) and brine (550 mL). The organic layer was dried over MgSO4, filtered and concentrated under reduced pressure to 35 g (90%) of the chlorosulfonamide 7 as a yellow viscous oil. HPLC analysis showed a purity of 95%. 1H NMR (300 MHz, CDCl3) δ 7.3-7.7 (m, 10H), 4.6-4.8 (m, 1H), 3.6-4.0 (m, 5H), 2.9 (s, 3H), 1.1 (s, 9H).
