Reaction #487583

Reaction equation

dimethyl 7-oxo-6,7,8,9-tetrahydro-5H-benzo[7]annulene-6,8-dicarboxylate

KOH

→

8,9-dihydro-5H-benzo[7]annulen-7(6H)-one

Yield 57.0%

Solvents

ethanol

Conditions

Workup

1. 1
   TemperatureAfter cooling to ambient temperature
2. 2
   Otherthe volatiles were evaporated
3. 3
   workup.ADDITIONTo the residue was added 120 mL of 2N HCl at 0° C.
4. 4
   Extractionthe crude product was extracted by EtOAc (200 mL×2)
5. 5
   WashThe combined extracts were washed with brine
6. 6
   DryingAfter being dried (MgSO4)
7. 7
   Filtrationfiltered
8. 8
   Concentrationconcentrated
9. 9
   Otherthe residue was purified by flash column chromatography on silica gel (hexanes/EtOAc 8:1)

Procedure

The crude dimethyl 7-oxo-6,7,8,9-tetrahydro-5H-benzo[7]annulene-6,8-dicarboxylate was dissolved in 200 mL of ethanol (EtOH) and then 100 mL of 2 N KOH. The resulting mixture was refluxed at 85° C. for 17 h. After cooling to ambient temperature, the volatiles were evaporated. To the residue was added 120 mL of 2N HCl at 0° C., the crude product was extracted by EtOAc (200 mL×2). The combined extracts were washed with brine. After being dried (MgSO4), filtered, and concentrated, the residue was purified by flash column chromatography on silica gel (hexanes/EtOAc 8:1) to afford 6.6 g (57%) of 8,9-dihydro-5H-benzo[7]annulen-7(6H)-one as a white solid: mp 40-41° C.; 1H NMR (300 MHz, CDCl3) δ: 7.21 (m, 4H), 2.94-2.90 (m, 4H), 2.63-2.60 (m, 4H); LC-MS: 161 (M+H)+.

Source