[CH3:1][C:2]1[CH:7]=[C:6]([C:8]([F:11])([F:10])[F:9])[CH:5]=[CH:4][C:3]=1[CH:12]1[CH2:17][CH:16]([C:18]([O:20]C)=[O:19])[CH2:15][CH2:14][N:13]1[C:22]([O:24][CH3:25])=[O:23].[Br-].[Li+].C(N(CC)CC)C>C(#N)C.O>[CH3:25][O:24][C:22]([N:13]1[CH2:14][CH2:15][CH:16]([C:18]([OH:20])=[O:19])[CH2:17][CH:12]1[C:3]1[CH:4]=[CH:5][C:6]([C:8]([F:11])([F:9])[F:10])=[CH:7][C:2]=1[CH3:1])=[O:23]
Dimethyl 2-(2-methyl-4-(trifluoromethyl)phenyl)piperidine-1,4-dicarboxylate (8.9 g, 24.77 mmol) was dissolved in acetonitrile (80 mL). Water (1.6 mL), lithium bromide (17.21 g, 198.14 mmol), and triethylamine (13.73 mL, 99.07 mmol) were added. The mixture was heated at reflux for 2.5 h. After cooling it was diluted with water and extracted with EtOAc twice and the combined organic layer washed with water. The combined aqueous layer was acidified with 2 M HCl and extracted three times with EtOAc. The combined organic layer was dried over Na2SO4, filtered and evaporated to give crude 1-(methoxycarbonyl)-2-(2-methyl-4-(trifluoromethyl)phenyl)piperidine-4-carboxylic acid (7.79 g, 91%). MS m/z 344 (M−H)−
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