[Synthesis]
5'-Chloro-2'-hydroxy-[1,1'-biphenyl]-3-carboxylic acid (Compound 2a, 2.31 g, 9.3 mmol) was used as a raw material and suspended in a mixed solution of 50% sulfuric acid (15 mL) and acetic acid (120 mL). Subsequently, a solution of sodium nitrate (NaNO3, 1.70 g, 20 mmol) dissolved in 25% sulfuric acid (6.5 mL) was slowly added to this suspension. The reaction mixture was stirred at room temperature for 1 hour. Upon completion of the reaction, the mixture was diluted with water (150 mL) to induce precipitation of the product. The precipitate was collected by filtration, washed with water and dried to afford the target product 5'-chloro-2'-hydroxy-3'-nitro-[1,1'-biphenyl]-3-carboxylic acid (Compound 2b) as a yellow-green solid (2.53 g, 92% yield, 97% purity, HPLC Method B). The structure of the product was determined by 1H-NMR (DMSO-d6) δ: 7.58 (t, J = 7.7 Hz, 1H), 7.75-7.78 (m, 2H), 7.97 (td, J1 = 1.4, J2 = 7.7 Hz, 1H), 8.05 (d, J = 2.7 Hz, 1H), 8.09 (t, J = 1.5 Hz, 1H), 10.73 (s , 1H), 12.98 (s, 1H) ppm; 13C-NMR (150 MHz, DMSO-d6) δ: 123.75,124.23,129.22,129.48,130.75,131.28,134.21,134.24,135.91,136.48,137.80,149.17, 167.50 ppm; mass spectrum (MS) m/z [M-H]? : 292.0 Confirmed. |