Dess-Martin periodinane (12 g, 28.3 mmol) was added to a solution of Example 3 (3.0 g, 7.6 mmol) in THF (20 mL) and CH2Cl2 (30 mL) at room temperature. The reaction mixture was stirred at room temperature for 18 h and CH2Cl2 (50 mL), aq. 15% Na2S2O3 solution (25 mL), and aq. 2M Na2CO3 solution (25 mL) were added. The mixture was stirred for 1 h and the layers were separated. The organic layer was dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure to give 2.9 g (97%) of the Example 5.
