Step 1) Synthesis of 5-fluorobenzo[d]thiazole-2-thiol: 2,5-difluoroaniline (1.00 g, 7.75 mmol) and potassium ethylxanthate (2.73 g, 17.05 mmol) were dissolved in N,N-dimethylformamide (50 mL). The reaction mixture was heated to 120 °C for 10 hours. After completion of the reaction, the mixture was cooled to room temperature and diluted with deionized water (100 mL). The pH of the mixture was adjusted to 4-5 with 1 M hydrochloric acid, at which point a solid precipitated. The solid was collected by diafiltration and dried at 50 °C. Ultimately, 5-fluoro-2-mercaptobenzothiazole was obtained as a white solid (1.11 g, 76.5% yield) under vacuum. Mass spectrum (ESI, cation mode) m/z: 185.00 [M + H]+; 1H NMR (DMSO-d6, 600 MHz) δ (ppm): 13.98 (s, 1H), 7.55 (d, J = 8.2 Hz, 1H), 7.36-7.31 (m, 2H).
