[CH3:1]C(C)([O-])C.[K+].[CH3:7][C:8](=[CH:12][CH2:13][CH:14]1[CH2:19][CH:18]2[C:16]([CH3:20])([CH2:17]2)[C:15]1([CH3:22])[CH3:21])[C:9](=[O:11])[CH3:10].CI.O>O1CCCC1>[CH3:7][C:8]([CH3:1])([CH:12]=[CH:13][CH:14]1[CH2:19][CH:18]2[C:16]([CH3:20])([CH2:17]2)[C:15]1([CH3:22])[CH3:21])[C:9](=[O:11])[CH3:10]5.0 g (43 mmol) of potassium tert-butoxide dissolved in 50 ml of tetrahydrofuran was added to the solution of 8.7 g (40 mmol) of 3-methyl-5-(1,2,2-trimethylbicyclo-[3.1.0]hex-3-yl)pent-3-en-2-one in 50 ml of the same solvent at -40° C. After 5 minutes of stirring at -35° C. 7.0 g (45 mmol) of methyl iodide was added rapidly and stirring continued at -20° C. for 10 minutes. The reaction mixture was poured on 200 ml of water and worked up as usual. Flash chromatography of the crude product (silica gel; eluent: hexane/MTBE 9:1) followed by Kugelrohr distillation at 150° C./0.1 Torr gave 7.3 g (78% yield) of 3,3-dimethyl-5-(1,2,2-trimethylbicyclo[3.1.0]hex-3-yl)pent-4-en-2-one.
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