反应详情

温度

-2.5 °C

To a suspension of methyl 3-acetyl-5-bromo-4-hydroxybenzoate (75 g, 258 mmol) in THF (350 mL) at −50° C. under nitrogen was added sodium bis(trimethylsilyl)amide (1M in THF) (904 mL, 903.58 mmol) over a 15 min period. The dark solution was allowed to warm to −5-0° C. and stirred for 1 h. Carbon disulfide (24.8 mL, 413 mmol) was added in one portion to the solution at −20° C. The mixture was allowed to warm to RT and stirred for 24 hrs. The reaction mixture was cooled to −50° C., quenched slowly with a 15% aq. sol. H2SO4 (750 mL) (need to trap the H2S formed). The reaction was extracted 3 times with ethyl acetate. The organic phase was washed with brine, dried over magnesium sulfate and concentrated. This residue was triturated with DCM (500 mL), collected by filtration, washed with ether and dried under vacuum to give methyl 8-bromo-4-hydroxy-2-thioxo-2H-chromene-6-carboxylate (33.5 g, 41%) as an yellow solid. The filtrate was evaporated and the resulting dark gum was triturated with ethyl acetate (300 mL) to give a solid which was collected by filtration washed with ether and dried under vacuum to give a second batch of methyl 8-bromo-4-hydroxy-2-thioxo-2H-chromene-6-carboxylate (17.5 g, 22%) as a orange solid. Mass Spectrum: [M−H]− 314 for both batches.

1. temperatureto warm to RT
2. stirringstirred for 24 hrs
3. temperatureThe reaction mixture was cooled to −50° C.
4. customquenched slowly with a 15% aq. sol. H2SO4 (750 mL) (need to trap the H2S
5. customformed)
6. extractionThe reaction was extracted 3 times with ethyl acetate
7. washThe organic phase was washed with brine
8. dry with materialdried over magnesium sulfate
9. concentrationconcentrated
10. customThis residue was triturated with DCM (500 mL)
11. filtrationcollected by filtration
12. washwashed with ether
13. customdried under vacuum