Under nitrogen protection, 100 g (0.62 mol) of 1,5-dihydroxynaphthalene (1) was dissolved in 500 mL (1.25 mol) of 10% NaOH solution and the reaction was carried out in a 2 L two-necked round bottom flask. Subsequently, 156 g (1.24 mol) of dimethyl sulfate was slowly added and the addition process lasted for 1 hour. After the reaction was carried out for 2 hours, the resulting precipitate was collected by vacuum filtration. The precipitate was sequentially washed twice with 200 mL of 5% KOH solution and three times with 200 mL of distilled water, followed by drying. The dried residue was completely dissolved in 1.5 L of benzene at 80 °C, which contained 300 g of activated carbon. The hot solution was filtered and left to cool to give 73 g of 1,5-dimethoxynaphthalene as white crystals. The product properties were as follows: yield 63%, melting point 181.9-182.3 °C, Rf value 0.49 [unfolding agent hexane:ethyl acetate (5:1)].1H-NMR (CDCl3, 400 MHz) data: δ 7.70 (d, J = 8.8 Hz, 2H), 7.38 (t, J = 8.0 Hz, 2H), 6.98 (d, J = 8.0 Hz , 2H), 3.94 (s, 6H).
