Synthesis
Step 1: Preparation of 4-hydroxycarbazole; Nickel Nguyenay (35 g) was added to a reactor equipped with 1 L of water, followed by 1,2,3,9-tetrahydrocarbazol-4-one (50 g) and sodium hydroxide (15 g). The reaction mixture was heated to reflux and maintained for about 20 hours. Upon completion of the reaction, the catalyst was removed by filtration and the filtrate was subsequently acidified to precipitate the solid product. The solid was collected by filtration and dried to give the crude 4-hydroxycarbazole. For further purification, the crude product can be dissolved in 10% sodium hydroxide solution, decolorized by activated carbon, and then the pH adjusted with dilute hydrochloric acid to precipitate the product. Finally, off-white to light gray 4-hydroxycarbazole crystals were obtained with a yield of about 50%.
References
[1] Journal of Organic Chemistry, 2006, vol. 71, # 22, p. 8384 - 8389
[2] Patent: WO2005/113502, 2005, A1. Location in patent: Page/Page column 14
[3] Bioorganic and Medicinal Chemistry Letters, 2002, vol. 12, # 20, p. 2957 - 2961
[4] Journal of the Chemical Society, 1955, p. 3475
[5] Journal of Labelled Compounds and Radiopharmaceuticals, 2005, vol. 48, # 6, p. 407 - 419
