Synthesis
General procedure for the synthesis of 2,5-dichlorobenzothiazole from 2-mercapto-5-chlorobenzothiazole: 5-chlorobenzothiazole-2-thiol (2 g, 9.9 mmol, purchased from Aldrich) was slowly added to thionyl chloride (20 mL, purchased from Aldrich) and stirred for 1 hour at room temperature. The reaction mixture was then heated to 50 °C and maintained for 15 minutes. Upon completion of the reaction, the mixture was cooled to room temperature, slowly poured into ice water and stirring was continued for 30 minutes. The reaction product precipitated out of the solution as a yellow solid and was collected by vacuum filtration, dried under a stream of air followed by high vacuum drying to afford 1.92 g of the target compound 2,5-dichlorobenzothiazole in 96% yield. The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 8.18 (d, J = 8.7 Hz, 1H), 8.1 (d, J = 2.0 Hz, 1H), 7.59 (dd, J = 8.7,2.1 Hz, 1H).
References
[1] Patent: US2005/250820, 2005, A1. Location in patent: Page/Page column 71
[2] Synthesis (Germany), 2018, vol. 50, # 10, p. 2027 - 2032
[3] Patent: WO2014/176258, 2014, A1. Location in patent: Page/Page column 29
[4] Patent: WO2007/146066, 2007, A2. Location in patent: Page/Page column 88
[5] Patent: WO2009/55357, 2009, A1. Location in patent: Page/Page column 35
