[F:1][C:2]1[C:14]([F:15])=[C:13]([F:16])[C:12]([F:17])=[C:11]([F:18])[C:3]=1[O:4][CH:5]1[CH2:10][CH2:9][NH:8][CH2:7][CH2:6]1.[N+]([NH:22][C:23](N)=[O:24])([O-])=O.O>C(O)C>[NH2:22][C:23]([N:8]1[CH2:9][CH2:10][CH:5]([O:4][C:3]2[C:11]([F:18])=[C:12]([F:17])[C:13]([F:16])=[C:14]([F:15])[C:2]=2[F:1])[CH2:6][CH2:7]1)=[O:24]A solution of 4.0 g of 4-(2,3,4,5,6-pentafluorophenoxy)piperidine in 100 ml of 95% ethanol was treated with 1.73 g of nitrourea and then stirred at 65° C. for five hours. After cooling to room temperature, the reaction mixture was poured into water and extracted with ethyl acetate. The organic layer was washed with water followed by a saturated sodium chloride solution and dried over anhydrous magnesium sulfate. Filtration, followed by evaporation of the solvents afforded a residue which was purified by means of high pressure liquid chromatography (silica gel; elution with 5% methanol/dichloromethane). The resultant solid was recrystallized from hot isopropanol to yield 3.41 g (73.3%) of 1-aminocarbonyl-4-(2,3,4,5,6-pentafluorophenoxy)piperidine, m.p. 170°-172° C.
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