Methylation of Cyclohexane-1,3-dione at the C2-Position; 2,2-Dimethylcyclohexane-1,3-dione

Tritch, K. J.; Brown, C. D.; Shudy, J. E.; Noland, W. E. ChemSpider Synthetic Pages 2017, 813, 1.

Cyclohexane-1,3-dione (5.00 g, 44.6 mmol, 1 eq.) was dissolved in acetone (100 mL) in a round-bottomed flask. Potassium carbonate (13.6 g, 2.2 eq.) was added, and then the resulting mixture was placed in an ice bath, and stirred for 15 min. Methyl iodide (6.1 mL, 2.2 eq.) was added. The resulting mixture was gradually warmed from 0 ºC to reflux over 2 h, and then was refluxed for 18 h more. The resulting cloudy, white mixture was allowed to cool to room temperature, and was then separated by suction filtration. The filter cake was washed with dichloromethane (25 mL). The filtrate was concentrated on a rotary evaporator, dissolved in water (50 mL) and dichloromethane (10 mL), and then extracted with dichloromethane (2 × 25 mL). The filter cake was placed in a conical flask with water (100 mL) and dichloromethane (50 mL). The resulting mixture was stirred for 10 min. The combined dichloromethane portions were washed with brine (25 mL), dried with sodium sulfate, filtered, and then concentrated on a rotary evaporator. The resulting yellow oil (6.08 g) was separated by column chromatography (1:8–1:1 ethyl acetate:hexane on SiO2). The desired fraction was concentrated on a rotary evaporator, and then dried under vacuum (0.1 mm Hg, room temperature, 2 h), giving a white powder (3.17 g).