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

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).

1. customconsumption of starting material
2. temperatureThe reaction mixture was then cooled to 0° C. before the cautious addition of 50 mL water
3. additionthe contents of the flask were then poured into a 500 mL Erlenmeyer flask
4. additioncontaining 150 mL ice-cold 10% H2SO4
5. extractionThe mixture was then extracted with ether (2×200 mL)
6. washthe combined organics were washed successively with water (100 mL), and saturated aqueous NaHCO3 (100 mL)
7. dry with materialdried over Na2SO4
8. concentrationconcentrated under diminished pressure
9. customto give 6.05 g (quantitative) of the dimethylenone (Rf 0.55, 2:1 hexane/ethyl acetate)

ORD record

ord-b5b308eb1a65423b89528c7faaf3ab8d

Source dataset

uspto-grants-1998_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05808139