[Br:1][C:2](Br)=[C:3]1[CH2:8][CH2:7][N:6]([C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10])[CH2:5][CH2:4]1.C1COCC1.[Cl-].[NH4+]>CO.[Zn]>[Br:1][CH:2]=[C:3]1[CH2:8][CH2:7][N:6]([C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10])[CH2:5][CH2:4]1
tert-Butyl 4-(dibromomethylene)piperidine-1-carboxylate (64 g, 0.18 mol) was dissolved in methanol (438 mL) and THF (220 mL) and the solution was cooled to 0° C. Ammonium chloride (77.14 g, 1.44 mol) was added and the reaction was stirred for 30 min. Zinc dust (47.13 g, 0.72 mol) was added and the reaction mixture was stirred at RT for 2.5 h. The mixture was filtered and the filtrate was evaporated to dryness. The residue was purified by silica gel chromatography using 230-400 mesh silica gel (2% ethyl acetate in hexane) to give the title compound (33 g). 1H NMR (500 MHz, CDCl3): δ 5.99 (s, 1H), 3.40 (m, 4H), 2.38 (m, 2H), 2.23 (m, 2H), 1.47 (s, 9H).
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