Pyridine (0.38 ml, 4.65 mmol) and trifluoromethanesulfonic anhydride (0.39 ml, 2.32 mmol) were added to a solution of 5-(4-fluorobenzoyl)-6-hydroxy-2-methylsulfonylnaphthalene (0.4 g, 1.16 mmol), [prepared as described in Example 2, step 3 above], in methylene chloride (10 ml) at 0° C. After 0.5 h, additional amounts of pyridine (0.38 ml, 4.65 mmol) and trifluoromethanesulfonic anhydride (0.39 ml, 2.32 mmol) were added and stirring was continued. After 0.5 h, 1N sodium bisulfate was added and the stirring was continued for an additional 30 minutes. The organic layer was separated, washed with brine, and dried over sodium sulfate. The solvent was removed in vacuo to give 0.6 g of 5-(4-fluorobenzoyl)-6-trifluoromethylsulfonyloxy-2-methylsulfonylnaphthalene as an oil (90% yield).
