7-Bromo-3,4-dihydro-2H-pyrido[3,2-b][1,4]oxazine

Synthesis

3,4-Dihydro-2H-pyrido[3,2-b][1,4]oxazine (500 mg, 3.67 mmol) was used as starting material and dissolved in DMF (10 mL). To this solution was added N-bromosuccinimide (NBS, 719 mg, 4.04 mmol) at 0 °C. The reaction mixture was stirred continuously for 2 h at 0 °C. Upon completion of the reaction, the reaction was quenched with saturated aqueous NaHCO3 solution and stirring was continued for 20 min at 0 °C. The resulting precipitate was collected by filtration and the solid product was washed with water and dried under vacuum to afford 7-bromo-3,4-dihydro-2H-pyrido[3,2-b]-1,4-oxazine (549 mg, 2.55 mmol, 69.5% yield) as a brown solid. The product was analyzed by mass spectrometry (ESI+) with a measured value of 215.2 (M + H).1H NMR (300 MHz, CDCl3) δ: 3.50-3.58 (2H, m), 4.18-4.26 (2H, m), 4.82 (1H, brs), 7.10 (1H, d, J = 1.9 Hz), 7.72 (1H, d, J = 2.3 Hz).

References

[1] Patent: WO2018/30550, 2018, A1. Location in patent: Paragraph 0596
[2] Patent: EP2341052, 2011, A1. Location in patent: Page/Page column 40
[3] Acta Chemica Scandinavica (1947-1973), 1971, vol. 25, p. 3135 - 3143
[4] Patent: KR101576386, 2015, B1. Location in patent: Paragraph 0158-0160