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The procedure of Van Allan and Deacon, Org. Synth. Coll. Vol. IV, 569, was adapted. A mixture of 1,2-diamino-4-chloro-5-fluorobenzene (528 mg, 3.29 mmol, Aldrich), potassium hydroxide (202 mg, 0.36 mmol), carbon disulfide (280 mg, 0.36 mmol), 95% ethanol (3 mL) and water (0.45 mL) was heated under reflux for 3 h. Activated charcoal (120 mg) was then added cautiously, and after the mixture has been heated at the refluxing temperature for 10 min the activated charcoal was removed by filtration. The filtrate was heated to 60°-70° C., warm water (3 mL) was added, and then acetic acid (0.25 mL) in water (0.5 mL) was added with good stirring for 4 h. The mixture was placed in a refrigerator overnight to give a mixture of brown and white crystals. The brown crystals were removed by washing with chloroform (5 mL). Recrystallization from hot EtOH/H2O gave pure title compound (420 mg, 63.5%, purity >99.57% by HPLC) as a white cubic crystals; top: 294°-6° C. (sub. from 250° C.). IR (KBr, cm-1): 3443, 3131, 3075, 1618, 1506, 1487, 1462. 1H NMR (DMSO-d6): δ 7.169 (d, J=9 Hz, 1H); 7.245 (d, J=6.6 Hz, 1H); 12.758 (s, 2H). HRMS: calcd for C7H4ClFN2S (M+) m/z: 201.9766, Found: 201.9779.

1. temperaturewas heated
2. temperatureunder reflux for 3 h
3. customwas removed by filtration
4. temperatureThe filtrate was heated to 60°-70° C.
5. temperaturewarm water (3 mL)
6. additionwas added
7. additionacetic acid (0.25 mL) in water (0.5 mL) was added
8. customwas placed in a refrigerator overnight
9. customto give
10. additiona mixture of brown and white crystals
11. customThe brown crystals were removed
12. washby washing with chloroform (5 mL)
13. customRecrystallization from hot EtOH/H2O