Lithium diisopropylamide (10.9 mmol, 2M tetrahydrofuran) was added to a solution of piperidine-1,4-dicarboxylic acid mono-tert-butyl ester (1.00 g, 4.36 mmol) in tetrahydrofuran (25 mL) at 0° C. After 1.5 h 2-fluorobenzyl bromide (0.788 mL, 6.54 mmol) was added, the reaction mixture was allowed to warm to room temperature and stirred overnight. The reaction was quenched with the addition of water (10 mL) followed by 1M hydrochloric acid (10 mL). The aqueous layer was extracted with ethyl acetate (3×50 mL), the organic layers collected, concentrated under reduced pressure and crude product purified by column chromatography to give 0.330 g, (22 %) of 4-(2-fluoro-benzyl)-piperidine-1,4-dicarboxylic acid mono-tert-butyl ester. 1H-NMR (CD3Cl3, 300 MHz) δ 7.11-7.00 (m, 5H), 4.00 (br., 2H), 2.92 (s, 2H), 2.90 (br., 2H), 2.05 (br., 2H), 1.46 (br., 2H), 1.44 (s, 9H).
