Synthesis
The general procedure for the synthesis of 2,4-dichlorothiazole from 2,4-thiazolidinedione was as follows: 2,4-thiazolidinedione (50 g, 0.43 mol) was dissolved in phosphorus trichloride (240 mL) and cooled to 5 °C. Pyridine (34 mL, 0.43 mol) was added slowly over 15 minutes. The reaction mixture was heated to 125°C and maintained at this temperature for 4 hours. After completion of the reaction, it was cooled to 22°C. Excess phosphorus trichloride was removed by vacuum distillation. The residue was slowly poured into water (1 L) pre-cooled to 5°C. The aqueous phase was extracted with dichloromethane (3 x 400mL). The organic phases were combined and the solvents were evaporated to give the target product 2,4-dichlorothiazole (50 g, 76% yield).EI/MS m/z: (35Cl35Cl/35Cl37Cl/37Cl37Cl)153/155/157(M+1)+.
References
[1] Patent: WO2008/36579, 2008, A1. Location in patent: Page/Page column 36-37
[2] Patent: US2005/234046, 2005, A1. Location in patent: Page/Page column 60
[3] Journal of the American Chemical Society, 2013, vol. 135, # 5, p. 1986 - 1996
[4] Patent: WO2013/149362, 2013, A1. Location in patent: Page/Page column 55
[5] Patent: WO2017/155909, 2017, A1. Location in patent: Paragraph 0159
