2,3-Dihydro-1,4-dioxino[2,3-b]pyridine

Synthesis

a-1) Synthesis of 2,3-dihydro-[1,4]dioxohexa[2,3-b]pyridine 2,3-Dihydroxypyridine (2.22 g, 20.0 mmol) was dissolved in N,N-dimethylformamide (100 mL) and potassium carbonate (5.52 g, 40.0 mmol) was added at room temperature. After stirring for 5 min, 1,2-dibromoethane (2.6 mL, 30.0 mmol) was added slowly and dropwise at the same temperature. The reaction mixture was heated to 90 °C and the reaction was stirred overnight. Upon completion of the reaction, the mixture was cooled to room temperature and filtered to remove the insoluble salt. The filtrate was concentrated under reduced pressure to remove the solvent and the resulting residue was dissolved in ethyl acetate. The suspension was filtered, the filter cake was washed with ethyl acetate, the filtrates were combined and concentrated again under reduced pressure to give 2,3-dihydro-1,4-dioxo[2,3-b]pyridine (157 mg, 5.7% yield) as a colorless oil. 1H-NMR (CDCl3) δ: 4.26-4.28 (2H, m), 4.42-4.44 (2H, m), 6.94 (1H, dd, J = 5.6, 7.6 Hz), 7.28 (1H, dd, J = 1.2, 7.6 Hz), 7.69 (1H, dd, J = 1.2, 5.6 Hz).

References

[1] Patent: US2010/280013, 2010, A1. Location in patent: Page/Page column 49
[2] Patent: WO2015/42397, 2015, A1. Location in patent: Paragraph 000788