Reaction #89688

Reaction equation

phenylselenyl chloride

2-allylcyclopentanone

lithium bis(tri-methylsilyl)amide tetrahydrofuran

→

2-allyl-5-(phenylselanyl)cyclopentanone

Yield 71.0%

Solvents

tetrahydrofuran

tetrahydrofuran

Conditions

Workup

1. 1
   Othertemperature below −55° C
2. 2
   workup.ADDITIONOnce the addition
3. 3
   workup.STIRRINGthe mixture stirred at −60 to −70° C. for 30 min
4. 4
   Temperatureto warm to 0° C
5. 5
   OtherThe reaction was quenched by addition of the solution to a rapidly stirred mixture of ethyl acetate (500 mL) and 5% aqueous citric acid (200 mL)
6. 6
   Otherthe organic layer was separated
7. 7
   ExtractionThe aqueous solution was extracted with ethyl acetate (2×100 mL)
8. 8
   Washthe combined organic solution was washed with saturated aqueous sodium chloride (200 mL)
9. 9
   Dryingdried (MgSO4)
10. 10
    Concentrationconcentrated in vacuo
11. 11
    workup.DISSOLUTIONThe residue was dissolved in heptane
12. 12
    Washeluted with 2:1 heptane/dichloromethane

Procedure

While under a nitrogen, a solution of 2-allylcyclopentanone (12.4 g, 100 mmol) in anhydrous tetrahydrofuran (100 mL) was cooled to −70° C. and treated with 1 N lithium bis(tri-methylsilyl)amide/tetrahydrofuran (200 mL, 200 mmol) at a rate to keep pot temperature below −55° C. Once the addition was complete, the mixture was stirred at −60 to −70° C. for one additional hour. A second solution of phenylselenyl chloride (19.5 g, 102 mmol) in anhydrous tetrahydrofuran (50 mL) was added dropwise and the mixture stirred at −60 to −70° C. for 30 min, then allowed to warm to 0° C. The reaction was quenched by addition of the solution to a rapidly stirred mixture of ethyl acetate (500 mL) and 5% aqueous citric acid (200 mL), and the organic layer was separated. The aqueous solution was extracted with ethyl acetate (2×100 mL) and the combined organic solution was washed with saturated aqueous sodium chloride (200 mL), dried (MgSO4), and concentrated in vacuo. The residue was dissolved in heptane and loaded onto a silica gel column (˜600 cc) and eluted with 2:1 heptane/dichloromethane, then with 1:1 heptane/dichloromethane to afford 2-allyl-5-(phenylselanyl)cyclopentanone (19.7 g, 71%) as a pale yellow oil. NMR (CDCl3): δ 7.40-7.50 (m, 2 H), 7.05-7.25 (m, 3 H), 5.50-5.70 (m, 1 H), 4.80-4.95 (m, 2 H), 3.45-3.75 (m, 1 H), 2.30-2.50 (m, 1 H), 1.80-2.25 (m, 5 H), 1.50-1.75 (m, 1 H). MS (M+1): 279.1/280.9 (for 2 major isotopes of Se).

Source