反应详情

To a stirred solution of 4-bromo-o-phenylenediamine (3.1 g, 16.6 mmol) in 1-methyl-2-pyrrolidinone (150 mL) was added dropwise ethyl bromopyruvate at room temperature under nitrogen. After 20 hours, the reaction mixture was partitioned between water and diethyl ether. The organic phase was separated and the aqueous phase was extracted with diethyl ether twice more. The organic extracts were combined, washed twice with water, dried over magnesium sulfate, filtered, and the filtrate was concentrated to give an oil. The crude product was partially purified by flash chromatography over silica with dichloromethane to give a tan solid. The impure product was purified on a Chiralpak AS-H column with 95% carbon dioxide at 140 bar at 35° C. and 2 mL/min with 5% co-solvent (methanol:chloroform (80:20) to give 0.614 g (13%) of ethyl 6-bromo-2-quinoxalinecarboxylate as a tan solid. 1H NMR (CDCl3, 400 MHz): δ 9.52 (s, 1H), 8.37 (d, J=2 Hz, 1H), 8.16 (d, J=9 Hz, 1H), 7.93 (dd, J=9, 2 Hz, 1H), 4.59 (quartet, J=7 Hz, 2H), 1.50 (t, J=7 Hz, 3H). ESI-LCMS m/z 281 (M+H)+.

1. customthe reaction mixture was partitioned between water and diethyl ether
2. customThe organic phase was separated
3. extractionthe aqueous phase was extracted with diethyl ether twice more
4. washwashed twice with water
5. dry with materialdried over magnesium sulfate
6. filtrationfiltered
7. concentrationthe filtrate was concentrated
8. customto give an oil
9. customThe crude product was partially purified by flash chromatography over silica with dichloromethane
10. customto give a tan solid
11. customThe impure product was purified on a Chiralpak AS-H column with 95% carbon dioxide at 140 bar at 35° C.