The invention relates to a method of manufacture of dimiracetam (2,5-dioxohexahydro-1 H-pyrrolo[1,2-a]imidazole), characterized in that a 4-oxo-butanoic acid ester is condensed with glycinamide in a one-pot reaction with a controlled pH. The reaction may be performed in aqueous solution or in an anhydrous lower alcohol solution.