C(O)(=O)/C=C\C(O)=[O:5].[CH3:9][N:10]1[CH2:15][CH:14]=[C:13]([C:16]2[CH:21]=[CH:20][C:19]([CH3:22])=[CH:18][CH:17]=2)[CH2:12][CH2:11]1.[Br-].[Na+].BrBr.C(=O)([O-])[O-].[K+].[K+].[OH-].[Na+]>O.C(Cl)(Cl)Cl>[CH3:9][N:10]1[CH2:11][CH2:12][C:13]2([C:16]3[CH:17]=[CH:18][C:19]([CH3:22])=[CH:20][CH:21]=3)[CH:14]([O:5]2)[CH2:15]11-Methyl-4-(4-methylphenyl)-1,2,3,6-tetrahydropyridine maleate (5.0 g, 16.4 mmoles, described in Example 3) is suspended in water (60 ml) and a solution of sodium bromide (5.15 g, 49.9 mmoles) and bromine (0.84 ml) in water (50 ml) is added dropwise to the cooled mixture (<5° C.). The reaction mixture is stirred for 15 min., potassium carbonate (20 g) is added followed by chloroform (100 ml) and a solution of sodium hydroxide pellets (680 mg) in water (10 ml). After stirring vigorously for 15 min., the layers are separated and the aqueous solution is extracted with chloroform. The combined extracts are washed with brine, dried (MgSO4) and evaporated. The residue is triturated with pentane to give the title compound, mp 124°-125.5° C.
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