Reaktion #69491

Reaktionsgleichung

H2S

Carbon disulfide

H2SO4

methyl 3-acetyl-5-bromo-4-hydroxybenzoate

lithium bis(trimethylsilyl)amide

→

methyl 8-bromo-4-hydroxy-2-thioxo-2H-chromene-6-carboxylate

Ausbeute 63.5%

Lösungsmittel

DCM

Water

THF

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.STIRRINGthe mixture was stirred at room temperature overnight
2. 2
   Waschenthe THF layers was washed with water (2×350 mL)
3. 3
   Temperaturcooled to 0° C.
4. 4
   Sonstigeequipped with a bleach trap
5. 5
   Sonstigeformed
6. 6
   workup.STIRRINGThe mixture was stirred at room temperature for 3 h
7. 7
   workup.STIRRINGwas stirred at room temperature overnight
8. 8
   ExtraktionThe aqueous phase was extracted with DCM (2×)
9. 9
   Waschenwashed with brine
10. 10
    Trocknendried over MgSO4
11. 11
    Filtrationfiltered
12. 12
    Sonstigeevaporated
13. 13
    Sonstigeto afford an orange solid
14. 14
    SonstigeThis solid was triturated in diethyl ether
15. 15
    Filtrationfiltered
16. 16
    Sonstigedried

Vorschrift

To a suspension of methyl 3-acetyl-5-bromo-4-hydroxybenzoate (70 g, 243.52 mmol) in THF (700 mL) at −50° C. under nitrogen (flask equipped with a bleach trap) was added lithium bis(trimethylsilyl)amide (828 ml, 828 mmol). The dark solution was allowed to warm to −5° C. and stirred for 2 h. Carbon disulfide (22 mL, 365 mmol) was added in one portion to the solution at −20° C. then the mixture was stirred at room temperature overnight. Water (700 mL) was added, the THF layers was washed with water (2×350 mL). The aqueous phases were combined and cooled to 0° C. and quenched with H2SO4 (108 ml, 1948 mmol) in a vessel equipped with a bleach trap to neutralize the H2S formed. The mixture was stirred at room temperature for 3 h, DCM was added (700 mL) and mixture was stirred at room temperature overnight. The aqueous phase was extracted with DCM (2×). The organic phases were combined, washed with brine, dried over MgSO4, filtered and evaporated to afford an orange solid. This solid was triturated in diethyl ether, filtered and dried to give methyl 8-bromo-4-hydroxy-2-thioxo-2H-chromene-6-carboxylate (48.7 g, 63%) as a yellow/orange solid. Mass Spectrum: m/z [M+H]+=317.

Quelle