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The ethyl 8-methoxy-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-(trifluoromethyl)-2H-chromene-3-carboxylate (0.21 g, 0.49 mmole) was dissolved in THF (3 mL) and cooled to 0° C. (ice bath). Hydrogen peroxide (0.25 g, 0.074 mmole) followed by 2.5N sodium hydroxide (0.20 mL) was added dropwise and the resulting solution was stirred for 3 hours. The contents were poured into water (20 mL) and acidified using 2.4 N HCl to pH around 1 and extracted with EtOAc (2×20 mL). The combined extracts were washed with brine (20 mL), dried over MgSO4, filtered and concentrated in vacuo to give a yellow oil which was subject to flash chromatography (silica gel) and eluted with 0-35% EtOAc/ hexanes to give yellow solid (0.1 g, 65%). LCMS m/z 319.0 (M+H). 1H NMR (CDCl3/400 MHz) 7.58 (s, 1H), 6.50 (s, 1H), 6.29 (s, 1H), 5.66 (q, 1H, J=7.0 Hz), 4.29 (m, 2H), 3.86 (s, 3H), 1.32 (m, 3H).

1. additionwas added dropwise
2. extractionextracted with EtOAc (2×20 mL)
3. washThe combined extracts were washed with brine (20 mL)
4. dry with materialdried over MgSO4
5. filtrationfiltered
6. concentrationconcentrated in vacuo
7. customto give a yellow oil which
8. washeluted with 0-35% EtOAc/ hexanes