反応 #89690

反応方程式

sodium bicarbonate

boron trifluoride etherate

t-butyl carbamate

5-allylcyclopent-2-enone

t-butyl carbamate

→

tert-butyl 3-allyl-4-oxocyclopentylcarbamate

収率 27.2%

溶媒

heptane

dichloromethane

反応条件

後処理

1. 1
   workup.STIRRINGmixture stirred for 15 min
2. 2
   その他separated
3. 3
   抽出The aqueous solution was extracted with dichloromethane (2×20 mL)
4. 4
   洗浄the combined organic solution was washed with water and saturated aqueous sodium chloride (20 mL each)
5. 5
   乾燥dried (Na2SO4)
6. 6
   濃縮concentrated 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
   洗浄eluted first with 85:15 heptane/ethyl acetate
10. 10
    その他to afford
11. 11
    その他recovered
12. 12
    その他with 4:1 heptane/ethyl acetate to afford
13. 13
    ろ過filtered
14. 14
    その他to remove most of the t-butyl carbamate
15. 15
    workup.ADDITIONthe filtrate was added to a column of silica gel (˜300 cc)
16. 16
    洗浄eluted with 6:3:1 heptane/dichloromethane/ethyl acetate

実験手順

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.

出典