Hydrochloric Acid → 4-Oxo-3-phenyl-4H-pyrido[2,1-a]phthalazine-1-carboxylic acid

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Reaction Steps

11 g of methyl 4-oxo-3-phenyl-4H-pyrido[2,1-a]phthalazine-1-carboxylate are taken up in 300 ml of ethanol under argon, whereupon a solution of 3.7 g of potassium hydroxide in 30 ml of water is added thereto and the mixture is heated under reflux until the reaction has finished. The reaction mixture is then cooled to room temperature and poured into 2200 ml of water. The mixture is adjusted to pH 7 by adding 1N aqueous hydrochloric acid and impurities are removed by two-fold extraction with 300 ml of methylene chloride each time. The aqueous phase is acidified to pH 1 with 2N aqueous hydrochloric acid and the crystals formed are removed by filtration under suction. After repeated washing with water and drying in vacuo, there is obtained 4-oxo-3-phenyl-4H-pyrido[2,1-a]phthalazine-1-carboxylic acid as yellow crystals of m.p. 236°-237° (dec.).

Provenance & Evidence