General procedure for the synthesis of 1-(4-nitrophenyl)piperidin-4-ol from 4-hydroxypiperidine and p-fluoronitrobenzene: 4-hydroxypiperidine (2.12 g, 15.0 mmol) and p-fluoronitrobenzene (1.82 g, 18.0 mmol) were dissolved in N,N-dimethylformamide (DMF, 15 ml) and potassium carbonate (2.52 g, 18.0 mmol) was added . The reaction mixture was stirred at 85°C for 1 hour. After completion of the reaction, the solvent was removed by distillation under reduced pressure. Water was added to the residue which was then extracted with chloroform. The organic phase was dried with anhydrous magnesium sulfate and the solvent was again removed by reduced pressure distillation. The crude product obtained was purified by silica gel column chromatography (eluent: chloroform-acetonitrile) to give 1-(4-nitrophenyl)piperidin-4-ol (3.10 g, 93% yield). The melting point of the product was 115.6-117 °C. 1H-NMR (CDCl3/TMS) δppm: 1.62-1.74 (m, 2H), 1.99-2.02 (m, 2H), 2.87-2.95 (m, 2H), 3.47-3.54 (m, 2H), 3.82-3.88 (m, 1H), 6.85 (d, J=8.7 Hz, 2H), 7.19 (d, J=8.7Hz, 2H).
