Synthesis
General procedure for the synthesis of 2-bromo-5-hydroxybenzoic acid from 2-bromo-5-methoxybenzoic acid: 5 g of 2-bromo-5-methoxybenzoic acid (purchased from Wako Pure Chemical Industries, Ltd.) was refluxed with 15 g of aluminum chloride in 150 mL of chlorobenzene for 2.5 hours. After completion of the reaction, the reaction mixture was cooled and poured into ice water. The aqueous phase was extracted three times with 250 mL of diethyl ether. The organic phases were combined and concentrated under reduced pressure to remove the solvent to give 4.2 g of 2-bromo-5-hydroxybenzoic acid. Subsequently, 3.9 g of the resulting 2-bromo-5-hydroxybenzoic acid was dissolved with 3.9 g of resorcinol (purchased from Tokyo Chemical Industry Co., Ltd.) in 9 mL of aqueous 4M NaOH and heated at 60 °C for 30 min. To the reaction solution, 1.8 mL of 10% copper sulfate aqueous solution was added and heating was continued for 10 min. At the end of the reaction, the precipitate formed was collected by filtration to obtain a white powder of Urea A.
References
[1] Yakugaku Zasshi, 1956, vol. 76, p. 1122,1125
[2] Chem.Abstr., 1957, p. 3505
[3] Journal of Medicinal Chemistry, 2002, vol. 45, # 12, p. 2388 - 2409
[4] Patent: US5519133, 1996, A
[5] Journal of Agricultural and Food Chemistry, 2008, vol. 56, # 2, p. 393 - 400
