To a mixture of 5-chloro-2-hydroxy-benzaldehyde (3.15 g, 20 mmol), KI (0.1 g) and K2CO3 (8.28 g, 60 mmol) in DMF (100 mL) was added 4-methanesulfonyloxy-piperidine-1-caboxylic acid tert-butyl ester (7.26 g, 26 mmol). The mixture was heated at 100° C. for 2 h, then cooled to room temperature and partitioned between ethyl acetate and water. The organic layer was washed with 1N NaOH (30 mL), water, and dried over anhydrous Na2SO4, concentrated to give the title compound as white solid (Yield: 5.3 g, 78%).
