Synthesis
Anhydrous aluminum trichloride (110 mmol, 14.61 g) was added to a 250 mL three-necked flask under nitrogen protection, followed by the addition of 130 mL of dichloromethane. The reaction system was cooled to -78 °C and stirred at this temperature. A dichloromethane solution of 2-methyl-3-indane (100 mmol, 11.82 g) and 3-chloro-2-methylpropionyl chloride (100 mmol, 12.82 g) was added slowly and dropwise. After the reaction lasted for 24 h, the reaction mixture was slowly poured into dilute hydrochloric acid to terminate the reaction. The reaction mixture was washed sequentially with saturated aqueous sodium carbonate solution, water and saturated aqueous sodium chloride solution and then extracted with 100 mL of methylene chloride. The organic phases were combined and dried with anhydrous magnesium sulfate for 2 hours. After filtration, the solvent was removed by rotary evaporation and dried under vacuum to give 21.24 g of white solid in 95.4% yield. The resulting solid was slowly added to about 100 mL of concentrated sulfuric acid and heated to 85 °C for refluxing. After the reaction was completed, the reaction solution was slowly poured into about 500 mL of ice water, washed with saturated aqueous sodium carbonate solution to neutrality, and filtered to obtain 14.83 g of red solid in 83.4% yield. The above solid (79.6 mmol, 14.83 g) was dissolved in 100 mL of methanol, and sodium borohydride (160 mmol, 6.05 g) was added slowly and the reaction was stirred. After the reaction was completed, the methanol was evaporated, 100 mL of water was added, acidified with dilute hydrochloric acid, and then extracted with 200 mL of dichloromethane. The organic phases were combined and dried with anhydrous magnesium sulfate for 2 hours. After filtration, the solvent was removed by rotary evaporation and dried under vacuum to give 12.83 g of light yellow solid in 85.2% yield. The resulting solid (68 mmol, 12.83 g) was dissolved in about 150 mL of benzene, p-toluenesulfonic acid (1.3 mmol, 0.25 g) was added, and heated to 75 °C for reflux. Upon completion of the reaction, it was washed with saturated aqueous sodium carbonate to near neutrality and the organic phase was dried with anhydrous magnesium sulfate for 2 hours. The solid was removed by filtration, dried and dissolved in dichloromethane. Separation by column chromatography using petroleum ether as eluent gave 7.33 g of a pale yellow solid in 63.3% yield.
