Synthesis
General procedure for the synthesis of 3-bromo-2-chloroquinoline from 3-bromoquinolin-2(1H)-one: Phosphorus trichloride (3.42 g, 22.28 mmol) was slowly added dropwise to a stirred suspension of 3-bromo-1H-quinolin-2-one (4.16 g, 18.57 mmol) in acetonitrile (30 mL) at room temperature. The reaction mixture was heated to reflux for 3 hours. Upon completion of the reaction, it was cooled to room temperature, the reaction solution was carefully poured into crushed ice (70 mL) and the pH was adjusted to 9 with 10% potassium carbonate solution (40 mL).The resulting precipitate was collected by filtration, washed with water and dried under vacuum to afford 3-bromo-2-chloroquinoline as a white solid (4.00 g, 89% yield) with a melting point of 101-103 °C (literature value: 96-98 °C). The product was confirmed by 1H NMR (DMSO-d6, 400 MHz): δ 8.95 (s, 1H), 8.03 (d, 1H, J = 8.0 Hz), 7.98 (d, 1H, J = 8.8 Hz), 7.90-7.84 (m, 1H), 7.74-7.69 (m, 1H); 13C NMR (DMSO-d6, 400 MHz ) confirmed: δ 148.1, 145.4, 142.1, 131.3, 128.1, 127.8, 127.6, 127.2, 115.6. Elemental analysis (C9H5BrClN, Mr = 242.50): calculated values C 44.58, H 2.08, N 5.78; measured values C 44.46, H 2.07, N 5.79. LCMS (ESI+) m/z 242, 244 [M+H]+.
References
[1] Tetrahedron, 2013, vol. 69, # 45, p. 9512 - 9519
[2] Organic and Biomolecular Chemistry, 2016, vol. 14, # 40, p. 9622 - 9628
