Diethyl 2-(((6-methoxypyridin-3-yl)amino)methylene)malonate → Ethyl 4-hydroxy-6-methoxy-1,5-naphthyridine-3-carboxylate

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Reaction Steps

Dowtherm A (Fluka, 500 mL) was brought to boiling (250° C.) in a 2 L 3-neck flask fitted with a still-head and a reflux condenser. 2-[(6-Methoxypyridin-3-ylamino)methylene]malonic acid diethyl ester (100 g, 0.34 mole) was added portionwise over 5 min. The solution was heated at reflux for an additional 15 min, allowing some solvent to distil over. The resulting solution was cooled to room temperature and diluted with hexane (750 mL). The mixture was cooled in ice for 1 h, then the brown solid was filtered off, washed with hexane, and dried under vacuum to afford the title compound (61.72 g, 73%).

Provenance & Evidence