The general procedure for the synthesis of ethyl 4-bromo-6-methoxy-1,5-naphthyridine-3-carboxylate from ethyl 6-methoxy-4-oxo-1,4-dihydro-1,5-naphthyridine-3-carboxylate was as follows: ethyl 6-methoxy-4-oxo-1,4-dihydro-1,5-naphthyridine-3-carboxylate (6.3 g, 25.4 mmol) was suspended under nitrogen protection in N,N- dimethylformamide (DMF, 20 mL) with stirring at room temperature. Phosphorus tribromide (2.5 mL, 26.7 mmol) was slowly added dropwise and the reaction mixture continued to be stirred for 30 minutes. Upon completion of the reaction, the mixture was cooled in an ice bath and water (120 mL) was slowly added, followed by addition of saturated aqueous sodium bicarbonate to adjust the pH to 7. The precipitate was collected by vacuum filtration, washed with water and dried under vacuum. The crude product was purified by silica gel column chromatography (eluent tapered from cyclohexane 100% to cyclohexane/ethyl acetate 95/5) to afford ethyl 4-bromo-6-methoxy-1,5-naphthyridine-3-carboxylate (6.6 g, 21 mmol, 83% yield).LC-MS analysis showed the molecular ion peak (M-H+) of the target compound was 311.
![6-Methoxy-4-oxo-1,4-dihydro-[1,5]naphthyridine-3-carboxylic acid ethyl ester](/CAS/20180703/GIF/724788-63-0.gif)
