136888-20-5

652160-72-0

General procedure for the synthesis of 2-bromo-5-fluoro-3-nitropyridine from 2-hydroxy-3-nitro-5-fluoropyridine: 117 g of 2-hydroxy-3-nitro-5-fluoropyridine was divided into 4 batches (30 g x 3 and 27 g x 1) and treated with phosphorus tribromide (3 equiv; 163 g x 3 and 155 g x 1) and catalytic amount of N,N-dimethylformamide (15 mL), respectively. DMF was carefully added at room temperature with attention to gas release.After 5 min, the reaction mixture was heated to 110 °C and maintained for 3 h. The reaction mixture was then purified by LC/MS. Complete consumption of the feedstock was confirmed by LC/MS monitoring. After cooling the reaction mixture to room temperature, the reaction flask was placed in an ice bath. Ice was added to the flask slowly and carefully in batches, noting the escape of gas due to HBr generation. The resulting liquid and black solid were poured into the beaker containing ice. Ethyl acetate was added and the mixture was subsequently extracted several times with ethyl acetate. The organic layer was washed sequentially with saturated sodium bicarbonate solution, water and brine, dried over anhydrous sodium sulfate and filtered. The product was dried overnight in a vacuum pump to give 123 g of 2-bromo-5-fluoro-3-nitropyridine as a brown solid in 77% yield. Note: The reaction was completed in 1 h. 1H NMR (δ, CDCl3): 8.52 (m, 1H), 7.93 (m, 1H).