Synthesis
(2) 10.0 g of intermediate (II) was added to a three-necked flask containing 50 mL of ethanol, 4.8 g of iron powder was added, and refluxed for 0.5 hours. Subsequently, 1 mL of 6 mol/L sulfuric acid solution was slowly added dropwise. After the dropwise addition, the reaction was continued to reflux for 1 hour. After the reaction was completed, the pH of the reaction solution was adjusted to 8 with NaOH solution and cooled to 50 °C. Add 0.2 g of activated carbon and reflux for 0.5 h. Perform hot filtration into a crystallization flask and cool the crystals. The crystals were washed with ethanol and dried to give 9.60 g of intermediate (III) in 95.1% yield, melting point 96.3-98.2 °C.
References
[1] Journal of Chemical Research - Part S, 2002, # 12, p. 601 - 603
[2] Patent: CN108250091, 2018, A. Location in patent: Paragraph 0032; 0034; 0040
[3] Indian Journal of Chemistry, Section B: Organic Chemistry Including Medicinal Chemistry, 1994, vol. 33, # 7, p. 690 - 691
[4] Patent: CN106083621, 2016, A. Location in patent: Paragraph 0021-0025
[5] Patent: CN107935872, 2018, A. Location in patent: Paragraph 0034-0063; 0067-0074
