Preparation
1.1 Purification of Isophorone
Isophorone is a colorless, readily polymerizable liquid with a boiling point of 212–213 °C. It is prepared by condensation of acetone under alkaline conditions. Crude isophorone was collected by vacuum distillation at 84–85 °C/1.6 kPa, and stored in the dark for later use.
1.2 Synthesis of 2,3-Oxyphorone
55 mL of methanol (or ethanol), a certain amount of sodium hydroxide solution, and a phase transfer catalyst were added to a three-necked flask and stirred under an ice-water bath. 20.0 g of isophorone was slowly added dropwise using a constant-pressure funnel, maintaining the reaction temperature at 15 °C. After 20 min, the solution changed from beige to reddish-brown. At this point, 30% hydrogen peroxide was slowly added dropwise, maintaining the reaction temperature as before. After 10 min, the mixture was heated in a water bath, and the color of the reaction solution gradually lightened. The reaction was monitored by TLC.
After 1.5 h, the mixture was extracted three times with dichloromethane. The combined organic layers were washed twice with water and dried over anhydrous sodium sulfate. The organic solvent was first evaporated off, followed by vacuum distillation. The fraction collected at 81–83 °C/1.9 kPa was 3,5,5-Trimethylcyclohexane-1,2-dione, with a yield of 90% (literature value 84%).;
