Synthesis
General procedure for the synthesis of 2-chloro-6-nitrobenzothiazole from 2-chlorobenzothiazole: 11.08 g (6.42 mmol) of 2-chlorobenzothiazole and 8.56 mL of concentrated sulfuric acid were added to a 50 mL round-bottomed flask, and the reaction was stirred for 1.5 h at 10-17 °C. The reaction mixture became white. After the reaction mixture turned white, it was cooled to 12 °C, 714 mg (7.062 mmol) of potassium nitrate was slowly added, the reaction temperature was controlled to be lower than 18 °C, and stirring was continued for 1 hour. Subsequently, the reaction system was warmed to 25 °C, stirred for 1.5 h, and then slowly warmed to 40 °C. The progress of the reaction was monitored by thin layer chromatography (TLC) and after confirming the completion of the reaction, the mixture was cooled to room temperature and slowly poured into ice water. The precipitated solid was collected by filtration, washed with water to neutral (pH=7) and dried under vacuum to afford 2-chloro-6-nitrobenzothiazole in 87% yield.
References
[1] Bioorganic and Medicinal Chemistry Letters, 2005, vol. 15, # 14, p. 3328 - 3332
[2] Advanced Synthesis and Catalysis, 2017, vol. 359, # 11, p. 1837 - 1843
[3] Patent: WO2008/153325, 2008, A1. Location in patent: Page/Page column 36
[4] Beilstein Journal of Organic Chemistry, 2016, vol. 12, p. 2019 - 2025
[5] Farmaco, 1994, vol. 49, # 3, p. 153 - 166
