Tetrabutylammonium Fluoride → 5-Benzyloxy-2-fluoromethyl-pyran-4-one

To an ice/salt cooled solution of the sulfonate ester obtained in step 1 above ester (20.0 g, 64.4 mmol) in acetonitrile (120 mL) was added a mixture of a 75 wt % solution of tetrabutylammonium fluoride (35 g, 96.6 mmol) and 40 mL of acetonitrile. Additional tetrabutylammonium fluoride solution (35 g, 96.6 mmol) was added after 2.5 hrs and the reaction mixture was allowed to stir at room temperature for overnight. The reaction was concentrated in vacuo to give a dark red oil. The residue was diluted with 700 mL of ethyl acetate and washed 5 times with 120 mL of a 10% sodium hydrogen carbonate solution and twice with 120 mL of brine. The organic layer was dried over sodium sulfate, and concentrated to give a dark red oil. The crude product was purified by column chromatography on silica gel using a mixture of ethyl acetate and hexanes (1/1, v/v) as the eluant to give 5-benzyloxy-2-fluoromethyl-pyran-4-one as a waxy-like solid (10.0 g, 66% yield). 1H NMR (400 MHz, DMSO-D6) δ (ppm): 7.69 (s, 1H), 7.42-7.37 (m, 5H, H—Ar)), 6.57 (s, 1H), 5.36 (d, J=46.5 Hz, 2H, CFH2), 4.97 (m, 2H, OCH2).