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General procedure for the synthesis of 7-bromo-2-chloroquinoxaline from 7-bromo-2(1H)-quinoxalinone: 7-bromoquinoxalin-2-ol (2 g, 8.88 mmol) was added to dry phosphorus trichloride (7 mL) to form a suspension, followed by the addition of N,N-dimethylformamide (DMF, 2 drops). The reaction mixture was heated to 100 °C and the reaction was stirred at this temperature for 3 hours. After completion of the reaction, the mixture was cooled to room temperature. Excess phosphorous trichloride was evaporated under reduced pressure and the residue was dissolved in ethyl acetate (EtOAc) and added slowly dropwise to ice water under stirring. The aqueous phase was extracted three times with ethyl acetate, the organic layers were combined and washed with saturated sodium bicarbonate (NaHCO3) solution. Finally, the organic layer was concentrated to give 7-bromo-2-chloroquinoxaline as a solid product in 93% (2 g) yield.

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