Reacción #89690

Ecuación de reacción

sodium bicarbonate

boron trifluoride etherate

t-butyl carbamate

5-allylcyclopent-2-enone

t-butyl carbamate

→

tert-butyl 3-allyl-4-oxocyclopentylcarbamate

Rendimiento 27.2%

Disolventes

heptane

dichloromethane

Condiciones de reacción

Tratamiento posterior

1. 1
   workup.STIRRINGmixture stirred for 15 min
2. 2
   Otroseparated
3. 3
   ExtracciónThe aqueous solution was extracted with dichloromethane (2×20 mL)
4. 4
   Lavadothe combined organic solution was washed with water and saturated aqueous sodium chloride (20 mL each)
5. 5
   Secadodried (Na2SO4)
6. 6
   Concentraciónconcentrated in vacuo
7. 7
   workup.DISSOLUTIONThe residue was dissolved in minimum dichloromethane
8. 8
   workup.ADDITIONadded to a column of silica gel (˜300 cc)
9. 9
   Lavadoeluted first with 85:15 heptane/ethyl acetate
10. 10
    Otroto afford
11. 11
    Otrorecovered
12. 12
    Otrowith 4:1 heptane/ethyl acetate to afford
13. 13
    Filtraciónfiltered
14. 14
    Otroto remove most of the t-butyl carbamate
15. 15
    workup.ADDITIONthe filtrate was added to a column of silica gel (˜300 cc)
16. 16
    Lavadoeluted with 6:3:1 heptane/dichloromethane/ethyl acetate

Procedimiento

A stirred solution of 5-allylcyclopent-2-enone (2.20 g, 18 mmol), t-butyl carbamate (4.70 g, 40 mmol), and tetra-n-butylammonium bromide (6.45 g, 20 mmol) in anhydrous dichloromethane (40 mL) under nitrogen was cooled in an ice bath (3° C.) and treated dropwise with boron trifluoride etherate (2.22 mL, 18 mmol). The reaction mixture was allowed to warm to room temperature and stirred for 18 h. Saturated aqueous sodium bicarbonate (40 mL) was added and then mixture stirred for 15 min and separated. The aqueous solution was extracted with dichloromethane (2×20 mL) and the combined organic solution was washed with water and saturated aqueous sodium chloride (20 mL each), dried (Na2SO4), and concentrated in vacuo. The residue was dissolved in minimum dichloromethane and added to a column of silica gel (˜300 cc) and eluted first with 85:15 heptane/ethyl acetate to afford recovered starting material (0.3 5 g), then with 4:1 heptane/ethyl acetate to afford a mixture of t-butyl carbamate and subject compound. This mixture was warmed in heptane and filtered to remove most of the t-butyl carbamate, then the filtrate was added to a column of silica gel (˜300 cc) and eluted with 6:3:1 heptane/dichloromethane/ethyl acetate to afford tert-butyl 3-allyl-4-oxocyclopentylcarbamate 1.17 g (27%) as a pale amber solid. NMR (CDCl3): δ 5.60-5.75 (m, 1 H), 4.90-5.05 (m, 2 H), 4.50 (br s, 1 H), 4.00-4.25 (m, 1 H), 2.30-2.80 (m, 3 H), 2.20-2.30 (m, 1 H), 1.85-2.15 (m, 3 H), 1.38 (s, 9 H). MS (M+1): 240.1.

Fuente