[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][CH:11]([CH2:14][NH2:15])[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].[Cl:16][C:17]1[N:22]=[C:21]([Cl:23])[C:20]([Cl:24])=[C:19](Cl)[C:18]=1[Cl:26].C(=O)([O-])[O-].[K+].[K+]>CN(C)C=O>[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][CH:11]([CH2:14][NH:15][C:19]2[C:18]([Cl:26])=[C:17]([Cl:16])[N:22]=[C:21]([Cl:23])[C:20]=2[Cl:24])[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2]A stirred suspension of 1-t-butoxycarbonyl-4-(aminomethyl)piperidine (16.1 g, 75.0 mmol), pentachloropyridine (20.7 g, 82.5 mmol) and potassium carbonate (20.7 g, 150 mmol) in dimethylformamide (180 mL) is heated at 60° C. for 2 hours. Excess dimethylformamide is removed in vacuo and the residue is taken into water and chloroform. The phases are separated and the aqueous phase is extracted into chloroform (×2). The combined organic extracts are dried (sodium sulfate), filtered and concentrated in vacuo. Filtration through a silica plug eluting with a gradient of 30% diethyl ether-hexane then 60% diethyl ether-hexane provides 1-t-butoxycarbonyl-4-(2,3,5,6-tetrachloropyridin-4-ylaminomethyl)piperidine (18.5 g, 57%).
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