Potassium Iodide → Ethyl 6-iodoquinoxaline-2-carboxylate

Temperature

0 °C

To a mixture of compound 8 (1.37 g, 6.31 mmol) in a 50% aqueous fluoroboric acid solution (10 mL), at 0° C., was added dropwise, a solution of sodium nitrite (480 mg, 6.96 mmol) in water (3 mL). The reaction mixture was stirred for an additional hour at 0° C. and a solution of potassium iodide (1.57 g, 9.46 mmol) in water (5 mL) was added. The reaction was stirred at 0° C. for 1 h and then warmed at 50° C. until no more gas evolution was observed (1 h). After cooling to room temperature, the mixture was basified with a saturated aqueous sodium carbonate solution (60 mL) and extracted with dichloromethane (3×40 mL). The combined organic layers were washed with a 5% aqueous sodium bisulfite solution (2×30 mL), dried on magnesium sulfate, filtered and concentrated under vacuum. The crude product was purified by chromatography (Al2O3, CH2Cl2) to give compound 9 (0.68 g, 2.07 mmol) as a yellow solid. Yield 33%; Rf (Al2O3, CH2Cl2) 0.80; mp 160-162° C.; IR (KBr) ν 1103, 1151, 1230, 1237, 1717 cm−1; 1H NMR (400 MHz, CDCl3) δ 1.51 (t, 3H, J=7 Hz), 4.59 (q, 2H, J=7 Hz), 7.99 (d, 1H, J=9 Hz), 8.10 (dd, 1H, J=2.9 Hz), 8.62 (d, 1H, J=2 Hz), 9.51 (s, 1H); MS m/z 328 (M+, 19), 284 (43), 256 (100), 128 (29), 101 (50), 75 (30).

1. additionat 0° C., was added dropwise
2. stirringThe reaction was stirred at 0° C. for 1 h
3. temperaturewarmed at 50° C. until no more gas evolution
4. custom(1 h)
5. temperatureAfter cooling to room temperature
6. extractionextracted with dichloromethane (3×40 mL)
7. washThe combined organic layers were washed with a 5% aqueous sodium bisulfite solution (2×30 mL)
8. customdried on magnesium sulfate
9. filtrationfiltered
10. concentrationconcentrated under vacuum
11. customThe crude product was purified by chromatography (Al2O3, CH2Cl2)

ORD record

ord-48269f89069d40ed9a5e4a1a629f81f2

Source dataset

uspto-grants-2015_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09125937B2