Using 3-bromo-5-nitropyridin-2-ol (9.13 mmol, 2 g) as starting material, 2,3-dibromo-5-nitropyridine (2.23 g, 87% yield) was obtained by the reaction according to the synthesis of Intermediate 2 (Step B). The product was characterized by 1H NMR (300 MHz, CDCl3): δ 8.48-8.84 (m, 1H), 8.94-9.31 (m, 1H). eSI/MS analysis showed m/e of 267 [(M-I) , 100].
Synthesis of intermediate 7 (Method 2): 6-(3-methoxyphenyl)-5-phenylpyridin-3-amine. Step A: 3-bromo-5-nitropyridin-2-ol, POBr3 and PBr3 were heated and reacted at 120 °C for 3.5 hours. After completion of the reaction, the crude product was poured into an ice-water mixture and extracted with dichloromethane (DCM). The crude product was purified by fast chromatography on SiO2, eluting using a solvent mixture of hexane/ethyl acetate to give 2.63 g of the target product (73% yield). The 1H NMR (300 MHz, DMSO-d6) data of the product were: δ 8.95 (s, 1H), 9.18 (s, 1H).
