N([O-])=O.[Na+].[NH2:5][C:6]1[CH:11]=[C:10]([F:12])[C:9]([N:13]2[CH2:18][CH2:17][C:16](=[O:19])[CH2:15][CH2:14]2)=[C:8]([F:20])[CH:7]=1.[N-:21]=[N+:22]=[N-].[Na+].C([O-])(=O)C.[Na+]>Cl>[N:5]([C:6]1[CH:11]=[C:10]([F:12])[C:9]([N:13]2[CH2:14][CH2:15][C:16](=[O:19])[CH2:17][CH2:18]2)=[C:8]([F:20])[CH:7]=1)=[N+:21]=[N-:22]
Sodium nitrite (2.40 g, 35.30 mmol) was added to an ice cooled solution of 1-(4-amino-2,6-difluorophenyl)-piperidin-4-one (4.00 g, 17.69 mmol), obtained in Preparation 17, in 6 N HCl (10 ml) and the resulting solution was stirred at 0° C. for 0.5 h. The reaction mixture was quenched with an aqueous solution of sodium azide (2.30 g, 35.3 mmol) and sodium acetate (29.0 g, 353 mmol). The reaction mixture was extracted with ethylacetate (100 ml×2) and the combined extract was washed with water followed by brine. The ethylacetate extract was dried over sodium sulfate and concentrated under reduced pressure. The resulting residue was purified by column chromatography (ethylacetate/pet ether; 1:9) to yield the title compound (2.20 g, 55%).
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