Reaction #632025

Reaction equation

ethyl 2-(5-oxo-6,7,8,9-tetrahydro-5H-benzo[7]annulen-6-yl)acetate

potassium hydroxide

→

2-(5-oxo-6,7,8,9-tetrahydro-5H-benzo[7]annulen-6-yl)acetic acid

Solvents

ethanol

Conditions

Workup

1. 1
   Temperaturethe resulting mixture was refluxed for 2 h
2. 2
   Otherthe EtOH was removed by evaporation
3. 3
   ExtractionThe residue was extracted with EtOAc twice (15 mL×2)
4. 4
   OtherThe aqueous layer was then transferred into a flask
5. 5
   Temperaturecooled with an ice-water bath
6. 6
   workup.ADDITIONHCl was added dropwise
7. 7
   workup.ADDITIONEtOAc (60 mL) was then added
8. 8
   Otherthe layers were separated
9. 9
   Extractionthe aqueous layer was extracted with EtOAc
10. 10
    WashThe combined extracts were washed with brine
11. 11
    DryingAfter being dried (MgSO4)
12. 12
    Filtrationfiltered
13. 13
    Concentrationconcentrated

Procedure

The compound of formula (Db), ethyl 2-(5-oxo-6,7,8,9-tetrahydro-5H-benzo[7]annulen-6-yl)acetate, (6.6 g, 26.8 mmol) was dissolved in ethanol (EtOH) (30 mL), then 10% potassium hydroxide (KOH) aqueous solution (37.5 mL, 67 mmol) was added and the resulting mixture was refluxed for 2 h. After cooling to ambient temperature, the EtOH was removed by evaporation. The residue was extracted with EtOAc twice (15 mL×2). The aqueous layer was then transferred into a flask and cooled with an ice-water bath, con. HCl was added dropwise to adjust pH to about 2.0. EtOAc (60 mL) was then added, the layers were separated, and the aqueous layer was extracted with EtOAc. The combined extracts were washed with brine. After being dried (MgSO4), filtered, and concentrated, the compound of formula (Dc), 2-(5-oxo-6,7,8,9-tetrahydro-5H-benzo[7]annulen-6-yl)acetic acid, was obtained as an orange oil (5.7 g, 97%); 1H NMR (300 MHz, CDCl3) δ: 7.71-7.68 (m, 1H), 7.41-7.20 (m, 3H), 3.37-3.31 (m, 1H), 3.12-2.91 (m, 3H), 2.57-2.49 (m, 1H), 2.15-1.90 (m, 2H), 1.75-1.62 (m, 2H); LC-MS: purity: 100%; MS (m/e): 219 (MH+).

Source