3,5-Dimethylcyclohex-2-en-1-one → HCID 23529876, compound

Participants

Reaction Steps

A 1M solution of vinylmagnesium bromide in THF (90 ml, 90 mmol) was cooled in dry ice-acetone bath to −20° C. in an inert atmosphere and CuCl (4.45 g, 45 mmol) was added in one portion. The mixture was stirred for 30 min and a solution of 3,5-dimethyl-2-cyclohexen-1-one (41) (3.73 g, 30 mmol) in THF (40 ml) was added dropwise keeping the reaction temperature at −20° C. The cooling bath was removed and the reaction mixture was allowed to reach room temperature for 2 h. Saturated aqueous NH4Cl (50 ml) was added thoroughly while cooling with ice bath. Hexane (150 ml) was then added and the aqueous layer was separated and extracted with hexane (2100 ml). The combined organic extracts were washed with 20% aqueous acetic acid (100 ml) and with saturated aqueous NaHCO3 (3200 ml). The extract was dried over MgSO4, filtered and evaporated. The crude product was purified by flash chromatography on silica gel (light petroleum ether-ethyl acetate, 20:1) to give 42 (2.4 g, 52%) as a colorless oil. 1H-NMR (CDCl3, TMS): 0.99 (3H, d, 6 Hz, 5-CH3); 1.11 (3H, s, 3-CH3); 1.2-2.6 (7H, m, ring protons); 4.94 and 5.01 (total 2H, both d, 17 and 10.5 Hz, CH2═) and 5.64 ppm (1H, dd, 17 and 11 Hz, ═CH).

Provenance & Evidence