Preparation of 9-hydroxy-3- (2-hydroxyethyl) -2-methyl-4H-pyrido [1,2-a] pyrimidin-4-one and its crystals

A process for preparing 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 excess of 2-acetylbutyrolactone in chlorobenzene in the presence of a catalytic amount of an acid at reflux temperature while water formed during the reaction is removed azeotropically; b) processing the reaction mixture; c) allowing the 9-hydroxy-3- (2-hydroxyethyl) -2-methyl-4H-pyrido [1,2-a] pyrimidin-4-one crystallize while cooling; d) collecting and washing the crystals with chlorobenzene and drying in vacuo to give 9-hydroxy-3- (2-hydroxyethyl) -2-methyl- 4H-pyrido [1,2-a] pyrimidin-4-one; It is containing less than 0.3% residual 2-acetylbutyrolactone of.