O=P(Cl)(Cl)[Cl:3].CN([CH:9]=[O:10])C.[CH2:11]([O:13][C:14]([N:16]1[CH2:21][CH2:20][CH2:19][CH2:18][C:17]1=O)=[O:15])[CH3:12].C([O-])(=O)C.[Na+]>O>[Cl:3][C:19]1[CH2:20][CH2:21][N:16]([C:14]([O:13][CH2:11][CH3:12])=[O:15])[CH2:17][C:18]=1[CH:9]=[O:10]POCl3 (2.18 g, 23.4 mmol) was added very slowly to 2.7 ml of dry DMF at 0° C. The mixture obtained was stirred at 25° C. for 15 minutes. After the reaction temperature had been reduced again to 0° C., N-ethoxycarbonylpiperidone (11.7 mmol) was added. The reaction mixture obtained was stirred at 25° C. for 3 hours. Thereafter, sodium acetate (7 g) and water (8.5 ml) were added and the mixture was stirred. The reaction mixture was extracted with benzene. The organic phase was washed successively with water, sodium carbonate and saturated sodium chloride solution. After the organic phase had been dried over sodium sulfate, the solvent was removed under reduced pressure. The crude product obtained was employed in the next stage without further purification. The crude yield was 63%.
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