GENERAL STEPS: To a solution of 2-chloro-5-nitrobenzoic acid (0.500 g, 2.48 mmol) in dichloromethane (8.3 mL) was slowly added oxalyl chloride (0.239 mL, 2.73 mmol), followed by the addition of N,N-dimethylformamide (1 drop) as a catalyst. The reaction mixture was stirred at room temperature for 2 hours to complete the generation of the acyl chloride. Subsequently, triethylamine (0.691 mL, 4.96 mmol) was added to the reaction system as a base, followed by the slow addition of a dichloromethane (1 mL) solution of pyridin-4-amine (0.467 g, 4.96 mmol). The reaction mixture was continued to be stirred at room temperature for 16 h to ensure complete amidation reaction. Upon completion of the reaction, purification was carried out by fast column chromatography using 0-100% ethyl acetate/hexane gradient elution to afford the target compound 2-chloro-5-nitro-N-(pyridin-4-yl)benzamide as a brown solid (0.401 g, 58% yield). The structure of the product was analyzed by 1H NMR (400 MHz, DMSO-d6) δ 11.10 (s, 1H), 8.64-8.45 (m, 3H), 8.37 (dd, J = 8.9, 2.8 Hz, 1H), 7.92 (d, J = 8.8 Hz, 1H), 7.73-7.61 (m, 2H); 13C NMR (101 MHz, DMSO-d6) δ 163.67, 150.56, 146.14, 145.04, 136.95, 131.40, 126.06, 124.00, 113.68; ESI-MS m/z 278 ([M + H]+) confirmed.
