Cl.[CH2:2]([N:9]1[CH2:14][CH2:13][C:12](=O)[CH:11]([C:16]([O:18][CH3:19])=[O:17])[CH2:10]1)[C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1.Cl.[OH-].[Na+]>C(O)CO>[CH3:19][O:18][C:16]([CH:11]1[CH2:10][N:9]([CH2:2][C:3]2[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=2)[CH2:14][CH2:13][C:12]21[CH2:5][CH2:4][CH2:3][CH2:2]2)=[O:17]A mixture of 20.0 gm (70.4 mMol) 1-benzyl-3-methoxycarbonyl-4-oxopiperidine hydrochloride in 60 mL ethylene glycol was cooled in an ice bath as 24 gm hydrogen chloride were added. The slurry was heated at 70° C. for 2 hours and was then poured into 200 mL ice water. The pH was adjusted to about 8 with 5N sodium hydroxide and the resulting mixture extracted well with diethyl ether. The organic extracts were combined, dried over sodium sulfate, and concentrated under reduced pressure to provide 21 gm 8-benzyl-8-azaspiro[4,5]decane-6-carboxylic acid methyl ester.
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