The general procedure for the synthesis of 5-methoxy-3-hydroxypyridine from 5-methoxy-3-pyridine pinacol borate was as follows: to a stirred suspension of sodium perborate tetrahydrate (7.86 g, 51.06 mmol) in water was added 3-methoxy-5-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)pyridine (4 g. 17.02 mmol) solution of THF/H2O (80 mL:80 mL) and the reaction was carried out at room temperature. The resulting reaction mixture was stirred at room temperature for 2 hours. Upon completion of the reaction, the reaction mixture was extracted with ethyl acetate (200 mL), followed by washing the organic layer with brine and drying over anhydrous sodium sulfate. The organic layer was concentrated under reduced pressure to give the crude product. The crude product was purified by column chromatography on silica gel (100-200 mesh) using a hexane solution of 20% ethyl acetate as eluent to give a final product of 1.5 g of 5-methoxypyridin-3-ol. LCMS analysis showed a molecular ion peak of 126 (M+H). Step 3 involved the conversion of 3-methoxy-5-hydroxypyridine to 3-methoxy-5-methoxymethoxypyridine.
