5-Bromonicotinic acid (10 g, 49.5 mmol) was dissolved in tert-butanol (100 mL) at 20 °C and triethylamine (15.2 g, 150 mmol) and DPPA (20.4 g, 74 mmol) were added. The mixture was stirred in toluene (100 mL) at 65 °C for 40 min, followed by heating to 100 °C under nitrogen protection for 22 h of reaction. After completion of the reaction, the mixture was cooled and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography using ethyl acetate/hexane as eluent to afford tert-butyl 5-bromopyridine-3-carboxylate (10.52 g, 78%) as a white solid.1H NMR (300 MHz, CDCl3) δ 8.32 (m, 3H), 6.97 (brs, 1H), 1.53 (s, 9H); MS (ES) m/z: 273, 275 (M+H+). Calculated analytical value C10H13N2O2Br: C, 43.98; H, 4.80; N, 10.26. Measured value: C, 43.88; H, 4.52; N, 10.20.
