To a solution of 101e (20 g, 63 mmol) in anhydrous THF (400 mL) was added 2.4 M solution of n-butyllithium in hexane (65 mL) at −78° C. under N2 atmosphere. The clear yellow solution was stirred at −17° C. for 3 hr, when it showed a deep red-orange color. The reaction solution was re-cooled to −78° C., stirred rapidly and a solution of N-fluorobenzenesulfonimide (29 g, 92 mmol) in anhydrous THF (100 mL) was added in dropwise over 10 min. The reaction mixture was stirred at −78° C. for 5 min, −20° C. for 30 min, then room temperature for 1 h. The reaction mixture was poured into 150 mL of 50% aqueous NH4Cl and extracted with 300 mL of EtOAc. The separated organic phase was washed with 150 mL of water and 150 mL of brine, dried over Na2SO4, filtered, and concentrated in vacuo to give a residue which was purified by silica gel chromatography using EtOAc/CH2Cl2=1:5 as eluent to afford 101f (7 g, 33%) as yellow solid. LCMS (ESI) m/z 336 (M+H)+. 1HNMR (300 MHz, CDCl3) δ 7.53 (d, J=1.6 Hz, 1H), 7.08 (dd, J=2.0, 12.0 Hz, 1H), 5.90 (s, 1H), 4.24 (dd, J=5.2, 10.8 Hz, 2H), 4.06 (s, 2H), 3.98-3.91 (m, 2H), 2.26-2.19 (m, 1H), 1.45-1.42 (m, 1H), 1.42 (s, 6H), 1.30 (s, 9H).
