General procedure for the synthesis of methyl 3-(piperidin-4-yl)benzoate hydrochloride from methanol and the compound (CAS: 726185-55-3): 500 mg (2.069 mmol) of 3-(4-piperidinyl)benzoate hydrochloride was mixed with 10 mL of saturated HCl methanol solution and the reaction was stirred at room temperature overnight. After completion of the reaction, the reaction mixture was concentrated by distillation under reduced pressure. The concentrated residue was mixed with 3 mL of isopropanol and stirred, followed by filtration. The filter cake was washed with ether and dried at 60 °C in a recirculating air dryer. A final 390 mg (74% yield) of colorless crystalline product was obtained, and thin layer chromatography (TLC) showed an Rf value of 0.34 (unfolding agent: EI D). Infrared spectra (IR, KBr press method) of the product showed a characteristic absorption peak of carbonyl (C=O) at 1728 cm-1 . Electrospray ionization mass spectrometry (ESI-MS) analysis showed a molecular ion peak (M+H)+ of 220, as well as peaks of (M+Cl+HCl) of 290/292/294 (corresponding to Cl2 isotope pattern).
