Carbon Disulfide → 6-fluoro-2H-imidazo[1,5-a]pyridine-3-thione

In a round-bottomed flask, (5-fluoropyridin-2-yl)methylamine dihydrochloride (600 mg, 3.0 mmol) was suspended in methanol (16 ml). Triethylamine (1.4 ml, 10.0 mmol) was added followed by carbon disulfide (1.4 ml, 23.2 mmol). The reaction mixture was stirred at reflux (oil bath temperature=75° C.) overnight then cooled to room temperature and then concentrated. The residue was partitioned between dichloromethane and water. The aqueous layer was extracted with dichloromethane then the organic layers were combined, dried over sodium sulfate, filtered and concentrated. The residue was absorbed on silica gel and chromatographed with EtOAc/hexanes (gradient 0-60% EtOAc) to afford 169 mg (33%) of 6-fluoro-2H-imidazo[1,5-a]pyridine-3-thione as an orange solid. 1H NMR (DMSO-d6, 300 MHz): δ (ppm) 13.47 (br. s., 1H), 8.04 (dd, J=4.9, 1.1 Hz, 1H), 7.43-7.56 (m, 2H), 6.88 (ddd, J=10.0, 7.9, 2.1 Hz, 1H).