25.3 g of 4a,5,8,8a-tetrahydro-1,4-naphthoquinone was suspended in 120 g of water, 33.6 g of O was added, and the reaction was heated to reflux and stirred for 3 hours. 57 g of dimethyl sulfate was added to the reaction solution slowly, and the reaction was continued to be heated and refluxed for another 5 hours after the reaction. The reaction solution was cooled down to room temperature, and then the reaction solution was extracted three times with 100 mL of n-hexane, and the combined organic phases were washed with water in order and saturated with saline water. The combined organic phases were washed with water, washed with saturated brine, dried with anhydrous sodium sulfate, filtered and evaporated, and the residue was purified by silica gel column chromatography to obtain 5,8-dimethoxy-1,4-dihydronaphthalene 25.1 g, yield 88%. 19 grams of 5,8-dimethoxy-1,4-dihydronaphthalene dissolved in 40 ml of DMSO, to the solution, add 3.4 grams of potassium tert-butanol, room temperature reaction for 6 hours, cooled to room temperature, the reaction solution was poured into 2 liters of ice water, with 100 ml of hexane extracted for three times, the combined organic phases sequentially washed with water, saturated brine, anhydrous sodium sulfate drying, filtration, evaporation and residue with silica gel column chromatography. The residue was purified by silica gel column chromatography to obtain 18 g of 5,8-dimethoxy-1,2-dihydronaphthalene in 95 % yield.
