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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 (1.62 g, 3.92 mmole) was dissolved in THF (25 mL) and cooled to 0° C. (ice bath). Hydrogen peroxide (0.67 g, 5.88 mmole) followed by 2.5 N sodium hydroxide (1.57 mL) was added dropwise and the resulting solution was stirred for 3 hours. The contents were poured into water (40 mL) and acidified using 2.4 N HCl to pH around 1 and extracted with EtOAc (2×40 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 0-100% EtOAc/hexanes to give yellow solid (0.84 g, 71%). GCMS m/z 302.0 (M+). LCMS m/z 303.0 (M+H). 1H NMR (CDCl3/400 MHz) 7.59 (s, 1H), 6.60 (s, 1H), 6.51 (s, 1H), 5.64 (q, 1H, J=7.0 Hz), 4.28 (m, 2H), 2.17 (s, 3H), 1.31 (m, 3H).

1. additionwas added dropwise
2. extractionextracted with EtOAc (2×40 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 0-100% EtOAc/hexanes