1303587-99-6

943995-31-1

106-93-4

1303587-99-6

To 4-amino-2-chloropyrimidin-5-ol (67; 3.75 g, 25.8 mmol) and 1,2-dibromoethane (4.85 g, 25.8 mmol) was added potassium carbonate (10.68 g, 77.4 mmol) in dichloromethane (2500 mL). The reaction mixture was heated to reflux for 4 hours. Upon completion of the reaction, the insoluble solids were removed by filtration. The filtrate was concentrated and the resulting residue was purified by column chromatography to afford the target compound 2-chloro-7,8-dihydro-6H-pyrimido[5,4-b][1,4]oxazine (68; 3.18 g, 72% yield). Mass spectrometry (ESI) analysis: calculated value (C6H6ClN3O): 171.58; measured value: 173 [M + H].