Synthesis
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).
Purification Methods
Crystallise it from EtOH, AcOH (m 178-180o) or *C6H6. Also distil it in a vacuum. [Beilstein 6 III 5266, 6 IV 6554.]
References
[1] Journal of Chemical Research, 2010, # 9, p. 520 - 521
[2] Israel Journal of Chemistry, 2014, vol. 54, # 5-6, p. 796 - 816
[3] Chemistry - A European Journal, 2015, vol. 21, # 9, p. 3701 - 3707
[4] Angewandte Chemie - International Edition, 2017, vol. 56, # 12, p. 3383 - 3388
[5] Angew. Chem., 2017, vol. 129, # 12, p. 3432 - 3437,6
