Lithium Bromide → 3,3-DI(3-Butenyl)cyclopentanone

Participants

Reaction Conditions

Reaction Steps

To a suspension of copper(I) iodide (2.6 g) and lithium bromide (1.2 g) in tetrahydrofuran (25 mL) was added dropwise a 0.5M tetrahydrofuran solution of 3-butenylmagnesium bromide (26.5 mL) under nitrogen atmosphere at −78° C. over 6 minutes, followed by stirring the reaction mixture at −78° C. for 40 minutes. Then, 5 minutes after addition of boron trifluoride diethyl ether complex (0.554 mL), to the reaction mixture was added 3-(3-butenyl)cyclopent-2-enone (0.6 g) obtained in Step 1. Half an hour later, after addition of boron trifluoride diethyl ether complex (0.250 mL), the reaction mixture was stirred at −78° C. for 2 hours, and further stirred at room temperature overnight after removing a dry-ice/ethanol bath. Then, after addition of saturated aqueous ammonium chloride solution and 28% aqueous ammonia solution, the reaction mixture was extracted with ethyl acetate. The organic layer was washed successively with aqueous ammonia solution and saturated brine, dried and concentrated. The residue was purified by column chromatography on silica gel to give 3,3-dibut-3-enylcyclopentanone (380 mg).

Provenance & Evidence