To a magnetically stirred mixture of 4-benzyloxyindole (13.80 g, 0.062 mol), tetrabutylammonium hydrogen sulfate (1.05 g, 0.0031 mol) and finely ground sodium hydroxide (2.72 g, 0.068 mol) in 100 mL of dichloromethane at 0° C., was added 2-fluorobenzenesulfonyl chloride (13.25 g, 0.068 mol). After 18 hours stirring at ambient temperature, 2-fluorobenzenesulfonyl chloride (3.96 g, 0.020 mol) and finely ground sodium hydroxide (0.82 g, 0.020) were added. One hour later, the reaction mixture was washed sequentially with water (2×100 ML) and an aqueous K2CO3 solution (2 M, 100 mL). The aqueous fractions were combined and extracted with CH2Cl2 (2×45 mL). The organic fractions were combined, dried over MgSO4 and concentrated in vacuo. The resulting solid was recrystallized from 10:2 ethyl acetate/hexanes (100 mL) to give 4-benzyloxy-1-(2-fluorobenzenesulfonyl)-1H-indole as an off-white powder (21.48 g, 91%). MP 117-120° C.
