2-Cyclohexen-1-one, 3-ethoxy-5,5-dimethyl- → 2-Cyclohexenone, 5,5-dimethyl-

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Reaction Steps

To a flame-dried 100 mL round-bottomed flask containing lithium aluminum hydride (0.95 g, 24.4 mmol, 0.5 mol equiv) in 35 mL anhydrous ether under nitrogen atmosphere at 0° C. was added 8.20 g (48.7 mmol) 3-ethoxy-5,5-dimethylcyclohex-2-en-1-one (7) portionwise through a syringe as a solution in 10 ml anhydrous ether. The reaction mixture was allowed to warm to room temperature, and after 4 h, TLC analysis indicated complete consumption of starting material. The reaction mixture was then cooled to 0° C. before the cautious addition of 50 mL water, and the contents of the flask were then poured into a 500 mL Erlenmeyer flask containing 150 mL ice-cold 10% H2SO4. The mixture was then extracted with ether (2×200 mL), and the combined organics were washed successively with water (100 mL), and saturated aqueous NaHCO3 (100 mL), dried over Na2SO4, and concentrated under diminished pressure to give 6.05 g (quantitative) of the dimethylenone (Rf 0.55, 2:1 hexane/ethyl acetate). 1H NMR (400 MHz, CDCl3) δ 1.05 (s, 6H, geminal-CH3 's), 2.23 (dd, 2H, CHCH2), 2.28 (s, 2H, COCH2), 6.03 (ddd, 1H, 2-H), 6.87 ppm (ddd, 1H, 3-H).

Provenance & Evidence