To a solution of (R)-tert-butyl 3-(2,3-difluoro-6-methyl-4-(trimethylsilyl)benzoyl)piperidine-1-carboxylate (2 g, 4.9 mmol) in THF (20 mL) was added TEAF (0.22 g, 1.5 mmol) in THF (5 mL) at 0° C. The mixture was stirred for 4 h, after which brine was added, and the mixture was extracted with Et2O. The organic layer was washed with brine and dried over Na2SO4, concentrated. The residue was purified by column chromatography on silica gel to afford (R)-tert-butyl 3-(2,3-difluoro-6-methylbenzoyl)piperidine-1-carboxylate (1 g, 61%). 1H-NMR δ 7.07 (m, 1H), 6.90 (m, 1H), 4.10 (m, 2H), 3.92 (m, 2H), 2.21 (s, 3H), 1.97 (m, 2H), 1.60 (m, 4H), 1.49 (s, 9H), 1.30 (m, 3H).
