Patent ID: 7723518

Claim:
A process for preparing crystalline 9-hydroxy-3-(2-hydroxyethyl)-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one substantially free of 2-acetylbutyrolactone comprising the steps of a) reacting 2-amino-3-hydroxypyridine with a slight molar excess of 2-acetylbutyrolactone while azeotropically removing the water formed during the reaction in an organic solvent selected from the group consisting of 4-methyl-2-pentanol; a mixture of xylene and 4-methyl-2-pentanol; and chlorobenzene; in the presence of a catalytic amount of an acid at reflux temperature to form 9-hydroxy-3-(2-hydroxyethyl)-2-methyl-4H-pyrido[1,2-a ]-pyrimidin-4-one; b) working up the reaction mixture wherein the working up step comprises adding an alcohol and heating to reflux; c) allowing 9-hydroxy-3-(2-hydroxyethyl)-2-methyl-4H-pyrido[1,2-a]-pyrimidin-4-one to crystallize while cooling; d) collecting and washing the crystals with the organic solvent and drying in vacuo, yielding 9-hydroxy-3-(2-hydroxyethyl)-2-methyl-4H-pyrido[1,2-a]-pyrimidin-4-one; containing less than 0.3% residual 2-acetylbutyrolactone by weight.