4-Bromo-3-methoxyphenol (5 g, 24.75 mmol) and pinacol ester of bisboronic acid (9.43 g, 37.13 mmol) were dissolved in dioxane (50 mL), and anhydrous potassium acetate (6.1 g, 74.25 mmol) and [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloride dichloromethane complex (2 g. 2.47 mmol). The reaction mixture was heated to 80 °C and stirred for 16 h under nitrogen protection. After completion of the reaction, it was cooled to room temperature, the reaction mixture was diluted with ethyl acetate (50 mL) and filtered through diatomaceous earth. The filtrate was concentrated under reduced pressure and the residue was purified by silica gel column chromatography (eluent ratio of petroleum ether: ethyl acetate = 1:1) to afford the target product, 3-methoxy-4-boronic acid pinacol ester phenol (17-c), as a pale yellow solid (2.8 g, 45% yield). The product was analyzed by mass spectrometry (LC-MS, ESI): m/z = 251 [M + H]+.
