Ethylene Glycol → 6-Bromo-2-tetralone ethylene ketal

HRID 1986614Notes

Reaction equation

HRID 1986614 reaction equation
[Br:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[CH2:8][C:7](=[O:12])[CH2:6][CH2:5]2.[CH2:13](O)[CH2:14][OH:15]>C1C=CC=CC=1.C1(C)C=CC(S(O)(=O)=O)=CC=1>[Br:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[CH2:8][C:7]1([O:15][CH2:14][CH2:13][O:12]1)[CH2:6][CH2:5]2

Participants

5

Reactant 2

HCID 174Ethylene GlycolHCID 27335536-Bromo-2-tetralone2×

Product 1

HCID 233778946-Bromo-2-tetralone ethylene ketalYield 78.1%

Reagents, catalysts & solvents 2

HCID 6101p-Toluenesulfonic acidCatalystHCID 241BenzeneSolvent

Procedure

To a solution of 6-bromo-2-tetralone (5.36 g, 23.8 mmol) in benzene (5 mL) was added ethylene glycol (1.46 mL, 26.1 mmol, 1.1 eq) and p-toluenesulfonic acid (1.5 mg, catalyst). The mixture was heated at reflux and a Dean-Stark trap was used to collect the water produced. After 6 hours, TLC (25% EtOAc/hexanes) showed no 6-bromo-2-tetralone (Rf˜0.5) left and a new spot (Rf˜0.6) formed. The reaction mixture was cooled to room temperature, washed with 10% aqueous NaOH (2 mL) and H2O (5×2 mL), dried (Na2SO4), and concentrated in vacuo. The crude residue was chromatographed on silica gel by eluting with 10% EtOAc/hexanes to give 5.0 g (78%) of 6′-bromo-3′,4′-dihydro-1′H-spiro[[1,3]dioxoiane-2,2′-naphthalene] as a brown oil. 1H NMR (300 MHz, CDCl3): δ 7.27 (s, 1H), 7.23 (d, 1H, J=8.1 Hz), 6.92 (d, 1H, J=8.1 Hz), 4.02 (s, 4H), 2.96 (t, 2H, J=6.9 Hz), 2.92 (s, 2H), 1.93 (t, 2H, J=6.9 Hz).

Workup

  1. temperatureThe mixture was heated
  2. temperatureat reflux
  3. customto collect the water
  4. customproduced
  5. waitleft
  6. customa new spot (Rf˜0.6) formed
  7. washwashed with 10% aqueous NaOH (2 mL) and H2O (5×2 mL)
  8. dry with materialdried (Na2SO4)
  9. concentrationconcentrated in vacuo
  10. customThe crude residue was chromatographed on silica gel
  11. washby eluting with 10% EtOAc/hexanes

Sources & evidence

ORD record
ord-c19b3f280bad45f8bb0e9c9f6673a1c8
Source dataset
uspto-grants-2009_06
Patent number
US07550467B2

Reaction notes

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