Ethyl orthoformate → 7-Aminopyrido[4,3-d]pyrimidin-4(3H)-one

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Reaction Steps

Crude 4,6-diamino-3-pyridylcarboxamide (9.2 g) is heated in purified (EtO)3CH (distilled from Na, 60 mL) at 170° C. for 1.5 d. After removing the solvent, the residue is dissolved in hot 2M NaOH, filtered, neutralized (conc. HCl) and cooled to give 7-amino-4-oxo-3H-pyrido[4,3-d]pyrimidine (3.57 g, 69% from the nitrile) as a light brown solid. 1H NMR (DMSO) δ 11.79 (1H, brs), 8.74 (1H, s), 7.97 (1H, s), 6.76 (2H, brs), 6.38 (1H, s).

Provenance & Evidence