The general procedure for the synthesis of 3-fluoro-4-hydroxypyridine from 3-fluoropyridine-4-boronic acid was as follows: under standard reaction conditions, CuSO4-5H2O (0.049 g, 0.2 mmol) and 6.7 mol% acetamide (20 mg) were dissolved in methanol, followed by addition of 2 mmol of phenylboronic acid. The reaction mixture was placed in an oil bath preheated to 60 °C and kept under constant stirring at atmospheric pressure. The reaction progress was monitored by thin layer chromatography (TLC). After completion of the reaction, the mixture was washed twice with hot ethyl acetate to remove unreacted reactants and by-products. After removal of hot ethyl acetate by evaporation, the crude product was purified by column chromatography on silica gel (260 mesh) with an eluent ratio of petroleum ether:ethyl acetate (25:75). The recovered catalyst could be used directly in the next round of reaction. The final product was structurally confirmed by 1H NMR and 13C NMR spectra.
