To a mixture of 7-bromo-4-hydroxy-2-oxo-2H-thiochromene-3-carboxylic acid methyl ester (Example 5 e) (220 mg, 0.70 mmol) in THF (8 mL) was added potassium benzyltrifluoroborate (138 mg, 0.70 mmol), Cs2CO3 (682 mg, 2.09 mmol), PdCl2(PPh3)2 (49 mg, 0.07 mmol) and then water (2 mL). The resulting mixture was refluxed overnight (18 h). After cooling, the reaction mixture was diluted with water (75 mL) and acidified using 1 N HCl to pH 4. The precipitate was collected, rinsed with water and the solid dissolved in CH2Cl2. The CH2Cl2 solution was dried over MgSO4, filtered, concentrated and the crude product purified by silica gel chromatography (5%-100% EtOAc/CH2Cl2) to provide 7-benzyl-4-hydroxy-2-oxo-2H-thiochromene-3-carboxylic acid methyl ester (99 mg). 1H NMR (200 MHz, CDCl3): δ (ppm)=15.2 (s, 1H), 8.25 (d, J=8.2 Hz, 1H), 7.36-7.16 (m, 7H), 4.04 (s, 2H), 4.00 (s, 3H).
