3,4-Dihydro-1H-[1,4]oxazino[4,3-a]benzimidazol-8-amine is a by-product in the synthesis of 4-(2,4-Diaminophenyl)-3-morpholinone (D416610) which is used in the synthesis of 5-Chloro-N-({(5S)-2-oxo-3- [4-(3-oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl}methyl)thiophene-2-carboxamide (BAY 59-7939) as an antithrombotic agent.