Allyl bromide → 2-Allylcyclopentanone

A stirred solution of methyl 2-carboxycyclopentanone (35.5 g, 250 mmol) in acetone (500 mL) was treated with anhydrous potassium carbonate (138 g, 1.0 mol) and allyl bromide (100 mL, 1.15 mol) and refluxed for 5 h. The mixture was cooled and filtered through Celite® (rinse filter cake with acetone), and the filtrate was concentrated in vacuo. The residual oil was dissolved in methanol (450 mL), treated with 6 N HCl (250 mL), and refluxed for 40 h. The solution was cooled to room temperature, concentrated in vacuo to remove most methanol, and diluted with water (200 mL). The aqueous solution was extracted with dichloromethane (3×250 mL), and the combined organic solution was washed with water, saturated aqueous sodium bicarbonate, and saturated aqueous sodium chloride (200 mL each), dried (Na2SO4), and gently (volatile product) concentrated in vacuo to 75 mL volume. This solution was loaded onto a silica gel column (˜500 cc) and eluted with dichloromethane to afford (after gentile concentration of fractions) 2-allylcyclopentanone (27.3 g, 88%) as a colorless oil. NMR (CDCl3): δ 5.65-5.75 (m, 1 H), 4.90-5.05 (m, 2 H), 2.40-2.50 (m, 1 H), 2.20-2.30 (m, 1 H), 1.85-2.15 (m, 5 H), 1.65-1.75 (m, 1 H), 1.45-1.55 (m, 1 H).

1. temperaturerefluxed for 5 h
2. temperatureThe mixture was cooled
3. filtrationfiltered through Celite® (rinse filter cake with acetone)
4. concentrationthe filtrate was concentrated in vacuo
5. dissolutionThe residual oil was dissolved in methanol (450 mL)
6. additiontreated with 6 N HCl (250 mL)
7. temperaturerefluxed for 40 h
8. concentrationconcentrated in vacuo
9. customto remove most methanol
10. additiondiluted with water (200 mL)
11. extractionThe aqueous solution was extracted with dichloromethane (3×250 mL)
12. washthe combined organic solution was washed with water, saturated aqueous sodium bicarbonate, and saturated aqueous sodium chloride (200 mL each)
13. dry with materialdried (Na2SO4), and gently (volatile product)
14. concentrationconcentrated in vacuo to 75 mL volume
15. washeluted with dichloromethane

ORD record

ord-2b7fb60892924ca693dbf6cb9543e8a5

Source dataset

uspto-grants-2016_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09440995B2