[OH:1][CH:2]([C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1)[CH2:3][CH2:4][C:5]([N:7]1[CH2:12][CH2:11][CH2:10][CH2:9][CH2:8]1)=[O:6].[Cr](Cl)([O-])(=O)=O.[NH+]1C=CC=CC=1>C(Cl)Cl>[O:1]=[C:2]([C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1)[CH2:3][CH2:4][C:5]([N:7]1[CH2:12][CH2:11][CH2:10][CH2:9][CH2:8]1)=[O:6]A mixture of 4-hydroxy-4-phenyl-1-piperidin-1-yl-butan-1-one (4.00 g, 16.2 mmol), prepared in the previous step, and pyridinium chlorochromate (5.23 g, 24.3 mmol) in 150 ml of methylene chloride was stirred at room temperature for 2.25 hours. The reaction was poured onto 400 g of silica gel (230-400 mesh) and the material eluted with methylene chloride-ethyl acetate. Isolation of the major component gave 4-oxo-4-phenyl-1-piperidin-1-yl-butan-1-one (3.66 g, 92%) as a green solid. Recrystallization of a portion of this solid from ethyl acetate-hexane gave an analytically pure sample, mp 52-54° C.
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