Example 1: Preparation of 4-(4-morpholinyl)benzoic acid by alkaline hydrolysis one-pot method using ethyl 4-fluorobenzoate and morpholine as raw materials. The procedure was as follows: ethyl 4-fluorobenzoate (3.5 g, 21 mmol) was mixed with morpholine (6.2 g, 70 mmol), and the reaction was heated at 130 °C for 12 hours until the ethyl 4-fluorobenzoate was completely converted. Subsequently, water (15 mL) and 20% NaOH solution (10 mL) were added to the reaction mixture and refluxing was continued for 3.5 hours. Upon completion of the reaction, the mixture was cooled to room temperature and acidified by adding 5% HCl solution with effective stirring. The precipitate was collected by filtration, washed with water and dried under vacuum at 60 °C to afford 4-morpholino benzoic acid (3.9 g) in 90% yield, melting point 275-277 °C. Mass spectrometric analysis showed the molecular ion peaks m/z 207 (100, M+).1H NMR (DMSO-d6) δ: 12.33 (br s, 1H), 7.78 (d, J=8.5 Hz. 2H), 6.95 (d, J=8.5 Hz, 2H), 3.72 (t, J=4.5 Hz, 2H), 3.23 (t, J=4.5 Hz, 2H).13C NMR (CDCl3) δ: 167.25, 153.90, 130.81, 119.91, 113.22, 65.87, 46.97.
