C(Cl)(=O)C(Cl)=O.CS(C)=O.[CH3:11][C:12]1[CH:25]=[CH:24][C:15]([CH2:16][N:17]2[CH2:22][CH2:21][CH:20]([OH:23])[CH2:19][CH2:18]2)=[CH:14][CH:13]=1.C(N(CC)CC)C.[Cl-].[NH4+]>C(Cl)Cl>[CH3:11][C:12]1[CH:13]=[CH:14][C:15]([CH2:16][N:17]2[CH2:18][CH2:19][C:20](=[O:23])[CH2:21][CH2:22]2)=[CH:24][CH:25]=1
To 2.8 mL (32 mmol) of oxalyl chloride in 75 mL of CH2Cl2 at −78° C. was added 4.6 mL (64 mmol) of DMSO. To this mixture was added 5.3 g (26 mmol) of 1-(4-methylbenzyl)-4-piperidinol 123 in 10 mL of CH2Cl2, and the mixture was stirred 5 min in the cold. The mixture was quenched with 18 mL (129 mmol) of triethylamine and allowed to come to room temperature, and saturated aqueous ammonium chloride was added. The organic phase was washed with water and brine, dried, and evaporated to give 4.27 g (81%) of 1-(4-methylbenzyl)-4-piperidinone (124), which was used as is without further purification. GC/MS showed 100% purity with a molecular ion of 203.
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