Synthesis
Methyl 5-bromo-2-naphthalenecarboxylate was synthesized as follows: 5-bromo-2-naphthalenecarboxylic acid (17.33 g, 69 mmol) was added to the reaction vial with methanol (250 mL) under nitrogen protection and stirred well. Subsequently, thionyl chloride (5.84 mL, 80 mmol) was added slowly dropwise at 25-30 °C, and the drop was completed in about 15-30 min, the reaction mixture showed light yellow color. The reaction mixture was heated to reflux for 3.25 hours. Upon completion of the reaction, the yellow solution was concentrated under reduced pressure to give 137.4 g of concentrate, which was subsequently placed in a refrigerator overnight for crystallization. On the following day, the thick mixture was obtained by filtration and the solid was washed with cold methanol (100 mL). The solid was dried under vacuum at 50 °C to give 11.39 g of the intermediate 5-bromo-2-naphthalenecarboxylic acid methyl ester as white crystals. The second product was treated by the same method and washed with cold methanol (100 mL) and dried to give 1.31 g of white crystals. The total yield was 69% and two batches of product were obtained.
References
[1] Synthetic Communications, 2011, vol. 41, # 13, p. 2017 - 2024
[2] Patent: US2004/6229, 2004, A1. Location in patent: Page/Page column 15
[3] Helvetica Chimica Acta, 1938, vol. 21, p. 62,65
[4] Journal of Medicinal Chemistry, 2004, vol. 47, # 8, p. 1893 - 1899
[5] Patent: WO2017/147328, 2017, A1. Location in patent: Paragraph 0328
