Example 17A1 Synthesis of 1-(2,2,2-trifluoroacetyl)piperidine-4-carboxylic acid: to a solution of piperidine-4-carboxylic acid (4 g, 30.97 mmol) in dichloromethane (20 mL) was added slowly and dropwise to trifluoromethanesulfonic anhydride (7.8 g) at 0 °C. The reaction mixture was stirred at 0 °C overnight. After completion of the reaction, the reaction solution was diluted with water, the organic layer was separated and concentrated. The crude product was purified by silica gel column chromatography to afford the title compound in 70% yield as a white solid.
